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BY
UJ/2006/EV/0199
MAY 2014

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CHAPTER ONE
INTRODUCTION
1.1
BACKGROUND TO THE STUDY
Dampness is the presence of unwanted moisture in the structure of a building, either the result of intrusion from outside or condensation from within the structure, the moisture penetrates vulnerable materials or finishes, dissolve soluble salts from the building materials such as calcium sulphate, and may also carry soluble salts from its source. Occupants of damp or mouldy buildings are at increased risk of experiencing health problems such as respiratory symptoms, respiratory infections, allergic rhinitis and asthma. A high proportion of the unwanted moisture enables the growth of various fungi and rot in wood, Plaster and paint deteriorate and wallpaper loosens. Stains from the water, salts and from mould mars surfaces.
Moulds can grow where there is a lot of moisture from structural problems such as leaky roofs or high humidity levels. Airborne mould concentrations have the potential to be inhaled and cause serious health effects in human. Dampness in buildings is caused by condensation, rain penetration or rising damp.
A damp proof course is a course of some impermeable material laid in the foundation walls of building near the ground to prevent dampness from rising into the building. It is a horizontal barrier in a wall designed to prevent moisture rising through the structure by capillary action. This is a course of material that is impermeable that is laid in the foundation walls of buildings near the ground, so as to avoid and prevent dampness from rising into the building. It can also be described as a waterproof membrane that is used as a protection against damp.

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In Nigeria today, especially in Jos North Local government area, where this research was carried out, so many houses visited randomly have dampness affecting it. This trend is dominant, more also that quacks are all over the place, who lack the techniques of construction. In the light of this, prospective landlords who want their lands developed would rather go for quacks to develop the land neglecting the basic standards. As such, faulty construction which will include seepage will occur. Forgetting to put in a DPC or putting it in at the wrong height is a very costly mistake that cannot be easily rectified. Historically
Buildings were built without a DPC. The inside walls, especially in the winter would be damp. Moisture un-checked, can & will rise up the wall to a height of approximately 1m.
(KCS, 2013) With the obvious desire to have a dry place to live some smart persons came up with the idea of incorporating a damp proof course in the walls. This was formed using a water impermeable material like Slate or Clay tile. Often this was just laid butted together & bedded in mortar. This produced a reasonable DPC. However, laid in a single course water could still by pass where the slates or tiles were butted together.
In some buildings 2- overlapping layers were used, thus making it an even more effective barrier. Modern buildings have a DPC that is made using a Bitumen re-enforced strip similar to roofing felt or Plastic; these come in various qualities depending on budget. (You get what you pay for). It is better using a DPC that is constructed using Elastomeric bitumen with a high tensile reinforcement. The type of DPC to be used depends on the site conditions on which the building is constructed as well as the building construction rules. ( Kcs, 2013)
However, most buildings in low-income countries are not lined with damp proof courses.
This could be as a result of poor enforcement of building regulations and also the cost of damp proof materials.

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In some countries worldwide, dampness in buildings are characterized by visible wetting of walls, ceilings and floors, blistering of paints, bulging of plaster, mould growth on surfaces and fabrics, rotten timber and sulphate attacks on brickworks (Trotman et al., 2004). Aside placing the performance of building structures under high risks (Oliver, 1997), the presence of dampness in buildings also have serious health implications on inhabitants living in the buildings (Palomaki & Reijula, 2008).
1.2 STATEMENT OF THE PROBLEM
It is observed that most buildings in low-income areas in Nigeria are not lined with damp proof courses because visible or physical deterioration on the wall are observed. It is observed in most buildings, deterioration on walls, paints, plaster, and seepage (rise in water level on the walls). This has made some landlords adopt the use of tiles to salvage this deterioration. However, this does not really make up for the solution to the lingering problem; rather it’s just a temporary measure which in no time will revert back by causing the tiles to develop cracks due to absorption of water. In addition, further observations shows that appliances, equipments, kitchen utensils made of metals are seen to have developed rust. This could be as a result of humidity been experienced. During the rainy season, it is observed that materials made of wool such as rug carpets develop stange which makes the occupant uncomfortable. This is indeed very worrisome. The type of DPC to be used depends on the site conditions on which the building is constructed as well as the building construction rules.
(KCS, 2013)
1.3 AIM AND OBJECTIVES
The aim of this research is to appraise the use of damp proof course (DPC) and membranes
(DPM) in residential buildings in Jos; A case study of Rusau and Angwa-Jarawa.
To achieve the aim of this research, the following objectives would be pursued;
(i) To determine the extent of use of DPC in residential buildings in the study area

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(ii) To assess the challenges and benefits of the use of DPC in residential building.
(iii)To assess the factors influencing the adoption of DPC/DPM.
1.4 SCOPE OF THE STUDY
The scope of this research is based on the use of damp proof course (DPC) and damp proof membrane (DPM) in some selected residential buildings in Jos, through physical inspection of the surface of these residential building and issue out questionnaire. The inspection of the
DPC will be at least 150mm from ground level (GL) using a measurable tape.
1.6 STUDY AREA
The study area is made up of two settlements, that is, Rusau and Angwan- Jarawa of Jos
North Local Area in Plateau State. The residential buildings in these settlements are mainly made up of bungalows, a few high- rise residential buildings.
1.7 JUSTIFICATION FOR THE RESEARCH
It is commonly observed in some parts of the country especially in the study area, buildings visibly seen with rise in damp on walls with defects such as deterioration of paints, plaster, rust visibly observed on metals in the room, mold growth. This could be as a result of faulty construction details or non compliance to details. This has necessitated the need to research into an assessment of the cause and remedial measures.

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CHAPTER TWO
LITERATURE REVIEW
2.1 THE CONCEPT OF DAMPNESS IN BUILDINGS
Dampness is the presence of unwanted moisture in the structure of a building, either the result of intrusion from outside or condensation from within the structure, the moisture penetrates vulnerable materials or finishes, dissolve soluble salts from the building materials such as calcium sulphate, and may also carry soluble salts from its source. Occupants of damp or mouldy buildings are at increased risk of experiencing health problems such as respiratory symptoms, respiratory infections, allergic rhinitis and asthma. A high proportion of the unwanted moisture enables the growth of various fungi and rot in wood, Plaster and paint deteriorate and wallpaper loosens. Stains from the water, salts and from mold mars surfaces.
Molds can grow where there is a lot of moisture from structural problems such as leaky roofs or high humidity levels (see plate 5). Airborne mold concentrations have the potential to be inhaled and cause serious health effects in human. Dampness in buildings is caused by condensation, rain penetration or rising damp.
Dampness in walls of buildings may lead to physical, biological or chemical deterioration of building materials. It is an important factor since it determines the quality of air in relation to human health and comfort and also the structural integrity of timber products in buildings
(Haverinen-Shaughnessy, 2007; King et al., 2000).Over the years dampness has received several definitions from different experts, but all point to one thing, that is, water present in

7 buildings which is not supposed to be there. According to The Canadian Wood Council,
CWC (2000), dampness can be defined as water penetration through the walls and certain elements of the building, especially where the building is close to a water source. Dampness is one of the subject areas littered with misconceptions and confusions over terminology and thinking (Halim et al., 2012; Burkinshaw & Parrett, 2004). According to Seeley (1994), dampness is the wetting of structural elements through moisture rise by capillary action. It can be described as excessive moisture contained within building materials and components which has the tendency to cause adverse movements or deterioration and which can result in unacceptable internal environmental conditions (Briffet, 1994). Dampness in a building also involves an excess of moisture that causes cosmetic problems, spoils decoration, deteriorate fabrics and causes structural problems or conditions that is of adverse effects to the health of occupants (Oxley, 2003). It is one of the most serious structural effects and can occur in the walls of both old and modern types of construction (Hetreed, 2008; Burkinshaw & Parrett,
2004). Dampness in walls spoils paints and interior decorations, encourages mould and rots growth, hampers aesthetics (see plate 4), poses threats to the health of occupants through providing breeding conditions for mosquitoes, bacteria and fungal growths. It undermines structural integrity of wall elements, reduces thermal insulation property of building materials as well as affects the comfort of the occupants (Trotman et al., 2004; Mbachu, 1999).
2.2 RISING DAMP
Water can enter a building in many ways, invariably causing damage to the building’s structure and decorations. One of the most common routes of entry is rising damp, whereby water from the ground is drawn up into the pores of bricks, mortar and other materials used to construct walls and floors (see plates 1and 3). The speed at which this process occurs depends on many factors, including the nature of the ground, type of wall or floor construction and environmental conditions both inside and outside the building. In most cases rising damp is

8 fairly slow to develop and may be present for several years before the appearance of damp patches, blistered paint, stained and peeling wallpaper, (see plate 4) or floor timbers rotted by fungal decay highlight the problem. (Rentokil Initial plc., 2009 ). The foundation of the building and the foundation walls are usually in direct contact with the sub-soil. The ground water level rises and drops depending on the season. This ground water rises through the fabric of the walling materials and passes through to the superstructure. This rising damp has the adverse effect of damaging fittings and finishes applied to the building. For this reason precaution should be taken to prevent this dampness from rising. The process of preventing the passage of moisture to the interior of a building through the walls, floors, etc. is referred to as damp proofing. Damp proofing is achieved by the use of damp proof course (DPC) and damp proof membrane (DPM). While the damp proof membrane (DPM) is defined as an impervious material placed horizontally at the floor level to prevent moisture penetration into the interior of the building (see plates 2 and 3). The movement of water or moisture into the building is most times upward through the foundation of wall from the ground. Paint laid
(D.P.C) should be protected on both sides with bitumen to prevent corrosion of the laid, as it is in contact with cement mortar. Care should be taken to ensure a good bonding between slate or brick and the mortar. (NBTE, 2008).

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Fig 1; Traditional treatments ( Rentokil, 2009 )
Fig. 2: Traditional treatment. ( Rentokil, 2009 )
The objectives with any rising damp treatment are to:

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(i) Prevent water from rising in walls above the level at which the new damp-proof course is installed
(ii) Deal with ancillary problems such as fungal decay, blocked wall cavities and plaster contaminated with hygroscopic (moisture-absorbing) salts carried up in the ground water
(iii) Prevent lateral movement of water to the internal face of cellars and basements below the level of the new damp-proof course
(iv) Provide a dry internal wall surface, suitable for decoration.
Treatments designed to meet these objectives have been many and varied, and include:
(i) Undercutting walls at an appropriate mortar joint line and inserting slate, bitumen or plastic
(ii) Installing an electro-osmotic system
(iii) Drilling and injecting the walls with an organic solvent based damp-proofing fluid.
These methods may be effective but may suffer from access or odour problems.
Attempts at camouflaging include coating the wall with a layer of metal foil, bitumen or sealer. In reality, this only serves to hide the dampness and its effects rather than curing the underlying cause.
2.2.1 Mold and Condensation In The Home
Mould is a fungal growth. It grows in homes under the right conditions of dampness, darkness & poor ventilation: e.g. bathrooms or kitchens, cluttered storage or basement areas, flooded areas, plumbing pipes and outdoors in humid environments. Walls, timber, carpet, furniture and fabrics can harbour mould if they stay damp for extended periods of time.
Indoor condensation can cause damage to fabrics, discolour paint (see plate 4) and wallpaper but, more importantly, it promotes conditions suitable for the growth of mould. When water is heated it changes into vapour. Condensation occurs when the vapour cools and changes it

11 back into liquid. When air is humid condensation will occur at the slightest drop in temperature. For example, the droplets of water that forms on the mirror or window of an unventilated bathroom while taking a hot shower or bath. In most Western Australian homes, indoor condensation is the main source of moisture for the growth of mould.
(New York City, 2000 ).
2.2.2 Health Effects Of Mold
Not all people are adversely affected by mould. However it can emit particles that may cause some people to sneeze. This is not necessarily an allergy; like a dust storm, it is a reaction to the particles in the air. Often, moulds can also release a musty odour which can be disagreeable. Toxic moulds produce mycotoxins that can pose serious health risks. Some studies claimed that exposure to high levels of mycotoxins can lead to neurological problems and in some cases death. Prolonged exposure may be particularly harmful.
A 2009 World Health Organisation report entitled "Children Living in Homes with Problems of Damp" stated that: "Excess moisture leads – on almost all indoor materials – to growth of microbes such as moulds, fungi and bacteria, which subsequently emit spores, cells, fragments and volatile organic compounds into the indoor air. Moreover, dampness initiates chemical and/or biological degradation of materials, which also causes pollution of the indoor air. Exposure to microbial contaminants is clinically associated with respiratory symptoms, allergies, asthma and immunological reactions. Dampness has therefore been suggested to be a strong and consistent indicator of risk for asthma and respiratory symptoms such as cough and wheeze." (New York City,2000.) Asthma is one of the most common health effects associated with dampness. Asthma is heightened due to condensation, moisture, humidity, and water intrusion, which all contribute to indoor moisture. Mould infestation is a major trigger for asthma. Another health effect associated with dampness is the presence of bacteria in an indoor environment. Bacteria require water to grow and multiply. Bacteria transmit

12 diseases, therefore putting occupants’ health at risk by water intrusion into the indoor environment. Water removal and drying of wet building materials within 4days will likely prevent mold and bacteria growth, therefore reducing occupants’ vulnerability to diseases.
Research in this area has not been conclusive (New York City, 2000).
Symptoms caused by mould allergy may include: i.
Respiratory illness or asthma; ii.
Watery, itchy, red eyes; iii.
Chronic cough; iv.
Headaches or migraines; v.
Rashes (dermatitis); vi.
Tiredness; vii.
Sinus problems, blocked nose; and viii.
Frequent sneezing;
Individuals with persistent health problems that may be fungi-related are advised to see their
GP for a referral to a practitioner trained in environmental medicine or related specialties and are knowledgeable about these types of exposures (New York City, 2000.)
2.3 CAUSES OF DAMPNESS
(i) Water introduced during construction : During bricklaying and plastering, tones of water are introduced into the walls. The wall remains damp until a hot season has passed.
(ii) Penetration of water through roofs, parapets and chimneys : roof may admit fine rain particularly in exposed situation. Roofs must be laid to an adequate pitch, securely fixed and with a generous overhang at eaves to present such penetration.

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Parapets and chimneys can collect and deliver water to parts of the building below roof level unless they have adequate damp-proof courses and flashings.
(iii) Penetration of water through walls : penetration occurs most commonly through walls exposed to the prevailing wet wind or where evaporation is retarded.
Sometimes the fault may be from a leaking gutter or down pipe.
(iv) Penetration of water through broken/decayed plumbing pipes placed in walls could also cause dampness.
(v) Rising damp : moisture from the ground rising in a porous wall may be caused by:- a) Absence of damp-proof courses.
Fig 3: Absence of DPC ii) Bridging of damp-proof course internally by floor screed laid which is not keyed to the
DPC. in the wall (Fig 12.2) or external rendering (Fig 12.3) which is liable to crack, and allow moisture to rise.

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Fig. 4: solid floor bridging DPC Fig 5: Bridging of DPC by External rendering iii) Bridging by earth deposited against the outside of a wall
Fig 6: Bridging by earth iv) Bridging caused by mortar dropping and other debris in cavity walls

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Fig 7: Bridging by mortar droppings
2.3 CONDENSATION
Condensation comes from water vapour within the building. Factors contribute to the condensation of water in buildings are: high humidity of indoor air, poor ventilation and low temperature of the walls and other surfaces.
Common sources may include cooking, bathing, dishwashers, etc. The moisture in the air condenses on cold surfaces, sometimes inside the walls called interstitial condensation. Buildings with poorly insulated walls are very prone to this problem. It often causes damage similar to damp in a building and often appears in similar places. This is because it occurs in the "dead air" pockets that accumulate in both horizontal and vertical corners (i.e. out of circulating air patterns).
Moisture condenses on the interiors of buildings due to specific interactions between the roof and wall. Leaks most commonly occur on flat-roofed buildings (Godish, Thad 2001). Certain building materials and mechanisms can be used to prevent condensation from occurring in these areas, therefore reducing structural dampness and potential mold infestation. In many cases, the insulation between the roof and wall is compressed, leading to a decrease in thermal resistance
(Prowler, Don, 2011). Due to the lack of thermal resistance, condensation occurs, which leads to water damage in the indoor environment. In most cases where moisture is not addressed

16 quickly enough, mold and mildew develop. Another issue is that wind washing up into the crevice where the roof and wall intersect reduces the efficiency of the insulation (Living With
My Home. Pillar To Post, Inc. Retrieved 20 November 2011). This results in condensation and risk for mold growth.
2.3.1 Controlling Condensation And Mould
The main ways of controlling condensation & mould are: i.
Ventilation ii.
Heating iii.
Insulation iv.
Removal a) Ventilation i.
Open windows and doors to ventilate the home and reduce the humidity level. Don’t forget the attic, basement and crawl spaces; ii.
Install and use mechanical ventilation (exhaust fans) that are vented to outside air, particularly in the bathroom and in the kitchen while cooking. This can eliminate much of the moisture that builds up from everyday activities; and iii.
Consider installing ventilation over appliances producing moisture, such as dryers, stoves, & kerosene heaters, or leave windows ajar while they are on. b) Heating i.
Keep indoor moisture low. Relative humidity should be below 60% (ideally
30%-50%). Relative humidity can be measured with a humidity meter, a small, inexpensive instrument available at most hardware stores; ii.
Maintain low constant heat when weather is cold or wet. Continuous, even heating is better than short bursts; and iii.
Install heating in the bathroom such as heat globes.

17 c) Insulation
Condensation forms more easily on cold surfaces, for example walls and ceilings. In many cases, those surfaces can be made warmer by improving insulation and insulate hot and cold surfaces, such as water pipes.
2.3.2 Removing Mould a) Eradicate mould when it occurs. It is hard to remove when it has been there a while; b) Do not dry brush the area. This could release spores into the air which can spread the mould further as well as cause an allergic reaction in some people; and
There are several treatments for mould: i.
Tea Tree Oil is effective. A 3% solution or 2 teaspoons in a spray bottle with 2 cups of water will suffice. Shake well before each use; ii.
Kill mould from surfaces with an 80% white fermented vinegar solution
(available from supermarkets). After applying the mixture, leave for at least 20 minutes and then lightly sponge with clean water; iii.
Remove the mould physically. Killing, but not removing the mould may
allow it to grow back; and don’t use bleach. Bleach has a high pH which makes it ineffective to kill mould. It simply bleaches it, so it looks like it has disappeared. a. Produce less moisture
1.
Put a lid on saucepans to keep the steam inside.
2.
Do not leave kettles boiling.
3.
Dry washing outside if possible. Otherwise, hang it up in the bathroom, close the door and have the window open or a fan working continuously while it dries.
4.
Try to avoid using paraffin or bottled-gas heaters that do not have an exhaust pipe to the outside. Burning paraffin or gas produces considerable amounts of water. b. Ventilate to remove moisture

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1.
Ventilate all rooms at regular intervals to remove humid air. Note that tight buildings require more active ventilation!
2.
Mechanical ventilation systems should not be stopped.
3.
Cooking, bathing and showering all produce steam. Open the window or put on the fan, and close the door to prevent the damp air circulating into other rooms.
4.
At other times, leave all the doors to different rooms open to allow the air to circulate.
5.
To avoid condensation in bedrooms, open the windows for 15 minutes each morning.
Human breathing puts considerable moisture into the indoor air.
6.
Move items of furniture away from the wall slightly so that air can pass behind them.
Leave the doors of cupboards open from time to time to air them.
7.
Do not ventilate cold basements when the outside temperature exceeds the inside temperature because the humidity of the warm air will condensate on the cold surfaces. In summer, only ventilate basements at night when outdoor temperatures have dropped. c. Insulate your building or heat your home a little more
1.
Thermal comfort ranges are very subjective. When at home, the ideal temperature usually ranges between 19-22 degrees Celsius in the living rooms, including the kitchen and bathroom, and 16-20 degrees Celsius in the bedrooms.
2.
When away from home, the temperature in the rooms should not drop under 15 degrees Celsius to avoid condensation and increased humidity levels.
3.
Do not heat up cold bedrooms in the evening by opening the door to heated rooms.
The warm and humid air will condensate on the cold walls of the bedroom.

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4.
Good insulation of the building helps preventing mould growth due to higher temperature of the walls. Again: note that tight windows and buildings require more active ventilation!
When the cause of the mould is related to building faults (leakages etc.) and/or the mould is also present in the building structure and material, it is recommended to get professional help.
In this case, it may be useful to consult a national or local source of information to guide you in your selection of a suitable contractor.
If mould growth is due to condensation and the mould area is less than 1m2 (i.e., 1 metre high by 1 metre wide or roughly 3 feet high by 3 feet wide) and is not caused by sewage or other contaminated water, you can probably manage the job yourself following these guidelines or some of those listed in the references, such as the guidelines of the US
Environment Protection Agency (EPA). Many national institutes have also published guidance documents in national languages (see examples in French, German and Spanish under “Further reading”). Whether the job is undertaken by a contractor or yourself, care has to be taken to avoid personal exposure to microscopic mould spores and the spread of spores within the building. If you yourself are undertaking the task of the mould removal, use a protective mask which covers your nose and mouth, wear goggles (without ventilation holes) to avoid getting mould or mould spores in your eyes, and protect your hands by wearing rubber gloves, preferably long ones. Chemical disinfection and the use of biocides are not recommended as a routine practice for mould control as it may be toxic for the occupants.
The application of disinfecting substances also does not solve the cause of the problem, and therefore may provide more health risks than benefits.
2.3.3 General Household Maintenance
1.
Check the roof for leaks and broken tiles regularly;
2.
Fix leaky plumbing as soon as possible;

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3.
Ensure weep holes on the outside of the building are not blocked. Weep holes allow drainage of water and the escape of vapour pressure from internal walls;
4.
Over winter and spring the weep holes in window frames (aluminium frames) can get clogged. If clogged, water will stand in the lower window frame sections;
5.
Check for doors or windows that may have broken seals;
6.
Ensure vents and air ducts are not clogged;
7.
Check for leaky toilets and that bathtub & kitchen sinks seals are undamaged;
8.
Swollen or crumbling walls or buckling floor boards should be removed; and
9.
Check for stained ceiling or wall tiles.
10.
Clean your bathroom frequently;
11.
Clothes & shoes must be dry before storing them;
12.
Clean evaporation trays in air conditioners, & refrigerators frequently; .Cool mist or ultrasonic humidifiers should be cleaned according to manufacturer's instructions and refill with fresh water daily;
13.
Wipe away moisture on windows and walls to keep your home dry;
14.
Carpets/rugs should be regularly aired & cleaned to prevent mould harbourage; and if flooding occurs it is important to clean & dry the area immediately or preferably within 24-48 hours to prevent mould growing. Water-damaged carpets & building materials can harbour moulds & bacteria. It may be necessary to remove the carpet as the mould may be impossible to remove completely.
Wardrobe/cupboard
· Allow plenty of ventilation in wardrobes. Leave doors open if possible.
· If your wardrobe has been affected by mould growth, investigate the source of moisture and treat as soon as possible. Remove mould and allow to completely dry.

21 i.
Use a semi-gloss paint on wooden surfaces. Untreated woods are more prone to moisture absorbency than semi-gloss painted surfaces and treated timbers. ii.
Consider installing sky lights in darker areas; iii.
Minimise the number of indoor plants; iv.
When filling your bath, add cold first, this reduces the steam produced; and v.
Let the sun into your home by opening curtains.
( New York City, 2000.)
2.3.4 Garden Maintenance i.
Don’t let the building foundation stay wet. Provide drainage from roof guttering and slope the ground away from the foundation of the building. ii.
Ensure garden beds are not higher than the foundation of the building. This will prevent moisture migrating into the wall. iii.
Clean roof gutters regularly. iv.
Downpipes should drain into soakwells to ensure drainage away from the house; v.
Prune overhanging trees near the roof.
Rentokil first developed a cost-effective chemical injection system in 1974, although the requirement for rigorous field testing prevented its complete introduction until 1980. The system was very effective, but Rentokil’s Research and Development Division continued to refine and improve the damp-proofing fluid and its method of application. The result is a new system which:
(i) Uses the latest and best materials
(ii) Uses water as the solvent with the associated benefits of low odour and low flammability
(iii) Takes into account health, safety and environmental regulations
(iv) Meets all of the stated objectives for an effective damp-proofing treatment.

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2.4 RISING DAMP TREATMENT
Before treatment is carried out, a careful survey is necessary to determine the following requirements:
(i) Joint or brick injection
(ii) Height at which the damp-proof course will be injected
(iii) Location of the injection points
(iv) Depth of the injection points
(v) Angle of the injection points, which should normally be horizontal
(vi) The quantity of fluid to be used.
These factors are important to ensure that the damp-proof course is installed in the correct position in relation to floor and ground levels, and that the fluid permeates sufficiently into the injected area to create a continuous horizontal damp-proof course (New York City, 2000.)
2.4.1 Joint brick/ block injection
It is also important to rectify other faults, which may be allowing the walls to become damp.
These may include faulty rendering, leaking rainwater disposal systems, high ground levels and poor drainage. Plaster which has become contaminated with salts, some of which may be hygroscopic, must be removed, while below the level of the damp-proof course it may be necessary to apply a specialised coating system to the walls and floors to prevent lateral movement of ground water into the area. This process is known as “tanking”.(
Rentokil , 2009)

23 fig 8: Brick injection
In many cases, damp is caused by "bridging" of a damp-proof course that is otherwise working effectively. For example a flower bed next to an affected wall might result in soil being piled up against the wall above the level of the DPC. In this example, moisture from the ground would be able to ingress through the wall from the soil. Such a damp problem could be rectified by simply lowering the flower bed to below DPC level. Where a rising damp problem is caused by a lack of a damp-proof course (common in buildings over approximately 100 years old) or by a failed damp-proof course (comparatively rare) there are a wide range of possible solutions available. These include:
 Replacement physical damp proof course
 Injection of a liquid or cream chemical damp proof course (DPC Injection)
 Porous tubes / other evaporative methods e.g. Schrijver
 Land drainage
 Electrical-osmotic systems
(a) Replacement physical damp proof course: A physical damp proof course made from plastic can be installed into an existing building by cutting into short sections of the mortar

24 course, and installing short sections of the damp proof course material. This method can provide an extremely effective barrier to rising damp, but is not widely used as it requires experienced contractors to carry out if structural movement is to be avoided and takes considerably longer to install than other types of rising damp treatment. The cost is also several times higher than for other types of rising damp treatment
(b) Injection of a liquid or cream chemical damp proof course (DPC Injection) : Injection of a liquid or cream into bricks or mortar is the most common method of treating rising damp.
Liquid-injection products were introduced in the 1950s and were typically installed using funnels (gravity feed method) or pressured injection pumps. The effectiveness of liquid injection damp proofing products is dependent on the type of formulation and the skill of the installer. In practice injection times tend to be lower than those required to provide a damp proof course of optimum effectiveness. A paper published in Building and Environment in
1990 made the following calculations about injection times: "The results of these calculations for a range of bricks and one building stone suggest that when high pressure injection is used the time of injection is unlikely to be less than five minutes per hole and may exceed 20 minutes per hole even for relatively permeable and porous materials. The times calculated for low pressure infusion of repellents range from 8 hours to 44 hours" (I'Anson, S J; Hoff,1990).
In more recent years patented damp-proofing creams EP patent 1106590 have taken over from liquid products due to improved ease of application. As with liquid products these are based on silane/siloxane active ingredients which line the pores of the mortar to repel damp.
The effectiveness of liquid and cream based rising damp treatments varies considerably between products due to variations in product formulations. Independent test certifications such as British Board of Agreement (BBA) certificates are available for some products, showing that they have met a minimum requirement for product performance.

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(d) Porous tubes: Porous tubes are installed along a mortar course. In theory these are supposed to encourage evaporation and reduce the rise of the damp. No independent test certification is available for this type of product and tests carried out by the Building
Research Establishment suggest that they are not effective at controlling rising damp. "Porous ceramic tubes were an early attempt to produce a method of combating rising damp; in the
1920s this technique was marketed by British Knapen. Tests were written up in the Building
Research Station Annual Report of 1930: 'There have been tests to determine the effect on the rate of evaporation of moisture of inclined porous clay tubes set in specimens of brickwork and natural stone. Laboratory experiments and field tests have been carried out. Results indicate that no useful increase in the rate of evaporation of moisture results from the use of these tubes.'(Trotman, et’al, 2014).
(e) Land drainage: It has been suggested that improving drainage around walls affected by rising damp can help to reduce the height of rise by reducing the amount of water available to be absorbed into the capillaries of the wall. Typically a trench would be excavated around the affected wall into which a porous pipe would be laid. The trench would then be back-filled with a porous material such as a single-sized aggregate, forming a French drain. Such a system would obviously have the practical disadvantage of being suitable only for the treatment of outside walls and would be impractical where other buildings are close by or where a building has shallow footings. Although the theory of reducing rising damp by reducing the amount of moisture in the underlying ground would appear to be sound, there is little data to suggest that it is effective in practice. Indeed, G and I Massari stated in the
ICCROM publication "Damp Buildings Old and New" that little effect was observed with
"open trenching" and no effect was observed with "covered trenching.’’ (G and I Massar,
2014)

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(f) Electrical-osmotic systems: These attempts to control rising damp through the phenomenon of electro osmosis. Whilst there is evidence to suggest that these systems can be useful in moving salts in walls (Ottosen, et’al, 2014) there is little in the way of independent data to demonstrate effectiveness in treating rising damp. The BRE publication
"Understanding Dampness" makes the following observations about electro osmotic systems for the treatment of rising damp: "There are two types: active and passive; neither has been approved by a recognised laboratory. By far the greater number of systems are of the passive kind, where there is no external source of electricity. They have always been something of a controversial issue. On theoretical grounds, it remains a mystery as to how they can work; their effectiveness has not been demonstrated in the laboratory and field evidence is disappointing.
(Trotman, et‘al, 2014).
2.5 DAMP PROOFING
Damp proofing in construction is a type of moisture control applied to building walls and floors to prevent moisture from passing into the interior spaces. Damp problems are one of the most frequent problems encountered in homes. Damp proofing is defined by the
American Society for Testing and Materials (ASTM) as a material that resists the passage of water with no hydro-static pressure and waterproof as a treatment that resists the passage of water under pressure (Greenlaw, Bruce, 2003). Generally damp proofing keeps moisture out of a building where vapour barriers keep interior moisture from getting into walls. Moisture resistance is not necessarily absolute: it is usually defined by a specific test method, limits, and engineering tolerances.
Damp proofing is accomplished in several ways including:
(i) A damp-proof course (DPC) is a barrier in a masonry wall designed to resist moisture rising through the structure by capillary action such as through a

27 phenomenon known as rising damp. The damp proof course may be horizontal or vertical (Punmia, B. C., A. K. Jain, and Arun Kumar Jain,2008) . A DPC layer is usually laid below all masonry walls, regardless if the wall is a load bearing wall or a partition wall.
(ii) A damp-proof membrane (DPM) is a membrane material applied to prevent moisture transmission. A common example is polyethylene sheeting laid under a concrete slab to prevent the concrete from gaining moisture through capillary action (Gorse, Christopher A., and David Johnston, 2012). A DPM may be used for the DPC.
(iii) Integral damp proofing in concrete involves adding materials to the concrete mix to make the concrete itself impermeable. (Punmia, B. C., A. K. Jain, and
Arun Kumar Jain, 2008 )
(iv) Surface coating with thin water proof materials for resistance to nonpressurized moisture such as rain water or a coating of cement sprayed on such as shotcrete which can resist water under pressure. (Punmia, B. C., A. K.
Jain, and Arun Kumar Jain, 2008 )
(v) Cavity wall construction, such as rain screen construction, is where the interior walls are separated from the exterior walls by a cavity. (Punmia, B. C.,
A. K. Jain, and Arun Kumar Jain, 2008 )
(vi) Pressure grouting cracks and joints in masonry materials.
2.6 DAMP PROOF COURSE (DPC)
All modern buildings have what is known as a Damp Proof Course. It is usually abbreviated to 'DPC', and in most buildings less than 30 years old, it consists of a DPM,

28 which is a Damp Proof Membrane, an impermeable layer of material, most often a polyethylene or bitumen-polymer, that is laid in the bedding joint between two courses of bricks. Its purpose is to prevent moisture from the outdoor environment and the ground rising up through the brickwork via capillary action, which can render the walls damp and the building unusable. Ground-level damp proof courses have been mandatory in all
British buildings since the Public Health Act of 1875. There are a number of alternatives to the modern DPC-on-a-roll, and these are sometimes found on older properties, particularly those built prior to the Second World War. The most commonly encountered alternatives are the brick damp course and the slate DPC. The brick DPC uses a clay brick with a very low absorption rate as a barrier to rising damp. The slate versions also rely on the impermeability of the slate to stop the 'wicking' of water via capillary action.
The "ground-level DPC" is actually required to be at least 150mm above the ground level.
This is to reduce the incidence of 'splash back' from rain, and to ensure a minimum amount of elevation above standing water that may come about in exceptionally heavy rain or other incidents, such as allowing the hosepipe to run unchecked.( NBTE, 2008)
Obviously some material must be built into the brick work and ground to prevent any water being drawn up above a level just above ground. The most convenient way of doing this is to build into horizontal or vertical joint some material which is non-absorbent or resistant to water and which is continuous. The materials most commonly used for this are:
Hard soil : Bitumen impregnated felt, Asphalt, Bituminous
Fairly firm soil: Lead / Aluminium core, A sheet of copper ; Polythene sheet ;
Lose soil: Metal sheet, concrete cement
Properties of damp proof course

29
· Flexibility
· Impervious
· Rigidity
· Durability
Damp proof course maybe horizontal or vertical placed either below the ground level or just above the ground level is in order prevent water raising up the wall of the building.
These below ground level are provided with the lowest floor in a building. (NBTE, 2008)
These consist of both horizontal and vertical D. P. C must be placed at least 150mm above the ground level and the vertical D.P.C must connect the two D.P.C form a completion barrier to moisture. Every wall in a building should have a (D. P. C) which is:

At least 150mm and above ground level

Above the surface of any oversite concrete

Below the surface member of the timber floor
Moreover the wall should be kept about 25mm away from asphalt and each course flushed up solidly. The asphalt which is laid on the floor slab should also have a protective screed on top to prevent any damage by people walking over it. Therefore, reinforcement is to be placed on it or petrol and oil being spilt from machinery.( NBTE, 2008)
Precaution to Be Taken When Laying DPC a) Always keep mortar bed even and ensure that there are no mortar littered on the floor b) Unroll bitumen material carefully; especially in cool weather as coldness tend to make them brittle and liable to crack badly. c) Bed slates and bricks carefully to ensure that there are no air puddles beneath them.

30
Procedure for Placing DPC
The DPC is placed horizontally below the ground level to prevent water up the wall. The
DPC below ground level is provided where the floor in a building is below the ground level and will consist of both horizontal and vertical DPC the lower DPC is placed below the floor level and an upper DPC is placed about 150mm above the ground level. The vertical DPC is connected to the two to form a complete barrier to the moisture rising up to the structure. As an impermeable membrane, the DPC prevents termites from penetrating through into the building. This is because it is a hard surface through which termite cannot penetrate. DPC will not allow any underground tree to penetrate through the ground to the floor. (NBTE, 2008)
Before the concrete is laid it is important to blind the top surface of the hard core. The purpose of this is to prevent the wet concrete running down between the lumps of broken brick or stone, as this would make it easier for water to seep up through the hard core. To blind the top surface of the hard core a thin layer of very dry coarse concrete can be spread over it, or a thin layer of coarse clinker (powder) or ash can be used. This blinding layer, or coat, will be about 50 mm thick, and on it the site concrete is spread and finished with a true level top surface. (Manjally, 2014)
2.7 HARD CORE
Hardcore application in the building process is also as important as any of the key stages .
Hard core is a measure involving the use of some large aggregates of stones (granite) during the process of building construction especially when constructing foundation or floor area.
In the majority of cases, broken blocks or bricks are used in this process, but are not recommended due to their strength. Hard core is applied after the internal part of

31 the foundation or floor area has been filled with some fine sands prior to the application of iron rods or wire mesh and concrete.( Manjally, 2014)
2.7.1 Importance of hard core
(i) Hard core helps to strengthens or solidifies the base of the building to resist the pressure of dead and live loads acting on the building.
(ii) Save cost of construction, i.e. the volume occupied by the hard core if it were to be concrete would have cost more.
(iii) Reduces movement of water up to the floor surface.
(Manjally, 2014)
2.8 TYPES OF DAMP PROOF COURSES
All materials used as damp proof courses should be resistant to moisture content. A damp proof course is cost effective and easily available. The type of DPC to be used depends on the site conditions on which the building is constructed as well as the building construction rules.
However, most buildings in low-income countries are not lined with damp proof courses.
This could be as a result of poor enforcement of building regulations and also the cost of damp proof materials.
The different physical DPCs include:
(i) Flexible materials such as hot bitumen, plastic sheets, bituminous felts, sheets of lead, copper,
(ii) Semi-rigid materials such as asphalt
(iii) Rigid materials such as impervious bricks, stones, slates, concrete painted with bitumen.

32
Chemical DPCs include:
This technique uses liquid like silicon compound which is either introduced into the wall by simple gravity or under pressure. The liquid will either fill the pores of a material with water resistant material (pore fillers) or line them with a non-absorbent surface to reduce capillary attraction (pore liners).
2.9 POSITIONING DAMP PROOF COURSES
The first DPC can be placed before the floor is laid or on the floor itself before the screed or tiles are laid but the former is better. The next layers of DPCs can be put under the windowsill and lintel. And if there is a floor above, another DPC can be placed under it.
Parapet walls and on top of wall plates would also need DPC to be installed.
2.9.1 Identifying Damp Proof Course
On some properties, identifying the DPC is quite straightforward: it protrudes slightly from the bed joint and could be spotted by the proverbial blind man on a galloping horse.
However, on other properties it can be less obvious and may take some poking about and investigating to pinpoint its position. Where the DPC doesn't jump out and announce its presence, there are a few key indicators that can help in identifying the position.
(i) On many established properties, the DPC will be somewhere between
100mm and 450mm above the paving or ground level
(ii) There is often a difference in brick type or brick appearance at the DPC
(iii) Air-bricks usually have their base resting on the DPC,
Sometimes there are a couple of traits that can confound the hunt for the DPC
(i) The DPC can be considerably more than 150mm above ground or paving

33 level
(ii) It can be stepped, changing level along the length of a building on sloping ground.
2.10 DAMP PROOF MEMBRANE (DPM)
Historically, floors were not protected & therefore were always damp. Later laying clay, slate or stone tiles, as a floor finish would offer some protection. Modern floors should have a water impermeable layer, usually in some form of plastic sheeting or bituminous product.
This membrane is fitted over a prepared over site/ subfloor prior to the concrete floor being laid. Any joins should be well lapped and taped with waterproof tape. At the perimeter walls it should be turned up & finished in line with the horizontal wall DPC. They usually require multiple coats to adequately cover. They are very effective since they are not prone to puncture in the same way as plastic sheeting. However, the quality is not in the product. It’s how well it’s applied. Experience has shown that a minimum of 3 coats need to be applied.
Any gaps or holes need to be well filled prior to application.
The installation of the damp proof course is a key stage of the building process, and one which really needs to be handled with care and attention to detail. Any faults with the installation, leading to damp ingress at a later stage, can be very expensive and difficult to fix. We recommend that only high quality damp proofing membranes that meet British
Standards, and other building accreditations, should be used as it is simply not worth the risk of using lower grade product for this essential function.
The Damp Proof Membrane (DPM) must be installed in conjunction with the Damp Proof
Course (DPC) in the outer walls so as to form a continuous layer. Where it is necessary to

34 join sheets of the DPM, first make sure that the surfaces to be joined are clean and free of moisture. Overlap the sheets by at least 4 to 6" (100 to 150mm) and use a double sided butyl tape or mastic strip compound to join the sheets together to form a continuous waterproof barrier. The exposed overlap joints can then be sealed using 4" (100mm) jointing tape. If any area of the DPM is damaged during installation this should be patched by overlaying a fresh piece of DPM to cover the damaged area and to overlap by at least 6" (150mm) in all directions. Once again use double-sided mastic strip, or butyl tape to create a waterproof barrier, and then seal down the edges with jointing tape.

35 fig 9: Hyload DPC jointing
The damp proof membrane should normally be covered with a layer of soft sand to act as a protection and to prevent damage when the concrete flooring or screed are installed.
Build base supply a complete range of damp proof course and damp proof membranes, including special membranes for use in areas with requirements for installation of Radon and other protective barriers.

36
The construction of most common ground floors fall into one of three categories; Ground
Supported Concrete Slab, Suspended Concrete and Suspended Timber.
New suspended floors are usually protected from dampness with a physical Damp Proof
Course. A Damp Proof Membrane is provided beneath a new Ground Supported Concrete
Slab to prevent the passage of moisture in the form of Rising Damp .
The Damp Proof
Membrane also aids with the curing of the concrete, helping ensure that construction water is not lost too quickly and that the concrete reaches its maximum strength.
When dealing with older buildings it is accepted that many floors such as flagstone floors and quarry tiled floors, do not benefit from the provision of a Damp Proof Membrane.
However, the density of the materials used can provide some resistance to the passage of rising Damp. When these old floors are covered with a vapour barrier, even with something as permeable as a carpet, problems can arise due to the restriction of natural evaporation.
The absence of a Damp Proof Membrane can result in timbers adjacent to damp floors being attacked by Wood Rotting Fungi and/or infested by Wood Boring Beetles. Discolouration of floor coverings and unpleasant odours associated with dampness can also be present.
With the introduction of moisture sensitive floor finishes such as timber and laminates etc, problems with dampness and defective/absent Damp Proof Membranes can have dramatic and costly consequences. Timber floor finishes expand when exposed to moisture, excessive exposure can cause the floor finish to buckle and cup leading to irreparable damage. Timber is hygroscopic and therefore even relatively low levels of moisture can cause problems with expansion. To protect a home is to provide a service to test existing solid floor slabs for the presence of moisture, the tests we carry out are very different to those used to identify if

37 walls are suffering from Rising Damp .
In the event that a floor is identified as suffering from dampness we have several options available for providing a remedial Damp Proof Membrane system. The system we select will be site specific and take account of many factors including existing floor construction, moisture content and surrounding construction. The end use of the area will also play a key role in the selection of an appropriate remedial Damp Proof Membrane system.
2.10.1 Liquid Damp Proof Membrane
As with plastic DPMs, the coating needs to be applied to the block/brickwork perimeter, up to the height of the horizontal damp proof course.
2.10.2 Materials
Materials widely used for damp proofing include:
(i) Flexible materials like butyl rubber, hot bitumen, plastic sheets, bituminous felts, sheets of lead, copper, etc.
(ii) Semi-rigid materials like mastic asphalt
(iii) Rigid materials like impervious bricks, stones, slates, cement mortar or cement concrete painted with bitumen, etc.
(iv) Stones
(v) Mortar with waterproofing compounds
(vi) Coarse sand layers under floors
(vii) Continuous plastic sheets under floors
2.10.3 Masonary Construction

38
A DPC is a durable, impermeable material such as slate, felt paper, metal, plastic or special engineered bricks bedded into the mortar between two courses of bricks or blocks. It can often be seen as a thin line in the mortar near ground level. To create a continuous barrier, pieces of DPC or DPM may be sealed together. In addition, the DPC may be sealed to the
DPM around the outside edges of the ground floor, completely sealing the inside of the building from the damp ground around it.
In a masonry cavity wall, there is usually a DPC in both the outer and inner wall. In the outer wall it is normally 150 millimetres (5.9 in) to 200 millimetres (7.9 in) above ground level (the height of 2-3 brick courses). This allows rain to form puddles and splash up off the ground, without saturating the wall above DPC level. The wall below the DPC may become saturated in rainy weather. The DPC in the inner wall is usually below floor level, (under a suspended timber floor structure), or, with a solid concrete floor, it is usually found immediately above the floor slab so that it can be linked to the DPM under the floor slab.
This enables installation of skirting boards above floor level without fear of puncturing it.
Alternatively, instead of fitting separate inner and outer DPCs, it is common in commercial house building to use a one-piece length of rigid plastic, (albeit an angled section), which fits neatly across the cavity and slots into both walls (a cavity tray). This method requires the need for weep vents to enable rainwater ingress to drain from the cavities otherwise rising dampness could occur from above the DPC (P.C. Varghese, 2005)
2.10.4 Concrete Walls And Floors

39
Concrete normally allows moisture to pass through so a vertical damp proof barrier. Barriers may be a coating or membrane applied to the exterior of the concrete. The coating may be asphalt, asphalt emulsion, a thinned asphalt called cutback asphalt, or a rubber polymer.
Membranes are rubberized asphalt or epdm rubber. Rubberized products perform better because concrete sometimes develops cracks and the barrier does not crack with the concrete.
(Greenlaw, Bruce, 2003)
2.10.5 Chemical damp proof course
There are a number of factors to be taken into account when considering chemical dampproofing systems and attendant replastering works. The following guide is intended to provide an objective insight into chemical damp-proofing, its performance and the importance of the replastering works. It should be fully appreciated that free water in building materials is not desirable, it can lead to decorative spoiling and rot: in some cases it can lead to collapse of the material itself, e.g., and cob. Indeed, someone saw fit at the end of the 1800's to stipulate the introduction of damp-proof courses as a whole and this practice is clearly an essential part of all properties constructed since that time; it certainly is now. If a damp-proof course was of no consequence it would not be necessary or be part of the
'Regulations' etc, and would not still be part of all new properties. Thus damp-proof courses are obviously beneficial to both the building and the occupants alike.
Another factor to consider is that, all things being equal, rising damp tends to rise higher in thick walls than thin walls; this is due to the lower surface to volume ratio of thicker walls, evaporation being mostly subject to surface area. This is an important feature to consider when dealing with properties with larger dimensioned walls - simply the so-called 'allowing walls to breathe' syndrome to stop the rising water may prove of little effect in such cases.
So there may be a case for chemical damp-proofing. Chemical damp-proof courses are

40 inserted to control the vertical passage of moisture from the ground and are almost all installed in properties where no damp-proof course exists or it has broken down with age.
Chemical damp-proof courses should be installed in a position in accordance with good practice as described in BS 6576:1985, "Code of Practice for the Installation of Chemical
Damp-proof Courses". They are installed in walls by various methods depending on the particular system being employed but the ultimate objective is to provide a water repellent or pore blocking material in a continuous horizontal band in the masonry thereby to provide a 'barrier' to water rising from the ground. Moisture paths the only continuous pathways through which water can rise through a wall are the mortar beds: for water to pass, say, from brick to brick it must still cross a mortar bed (bottom of figure, right). It is therefore essential that the damp-proofing material impregnates the mortar courses since these form the major pathway for the rise of water within walls. Damp-proofing the masonry units (eg, bricks) alone is of very little value! Porous mortar and impervious/water repellent brickwork will still allow rising dampness to occur. However, if the pores in the mortar line are made water repellent or blocked then the water cannot rise since it cannot traverse the mortar beds to do so (top figure, right). In the majority of older properties the mortar is not alkaline so that the water repellent formulations based either silicone resins, aluminium stearate, or methyl siliconate (sodium or potassium methyl siliconate) can be used. Occasionally, however, the mortar may highly alkaline such as in a recently constructed wall (eg. where the physical damp-proof course has been omitted). This will exclude the use of the methyl siliconates since the highly alkaline conditions found, for example, in new mortars prevent the formation of the water repellent resin. Care should be taken to ensure that the dampproof course is not bridged by high external ground levels, blocked cavities or debris piled against the wall; ground levels should be lowered, cavities cleaned out or the area below the

41 inserted damp-proof course might be 'tanked' internally if deemed necessary.
fig 10 : moisture pathway
When fluids are injected into a heterogeneous substrate such as brick/mortar they do not totally Viscous fingering fill up the porous structures and neither do they completely push out the water in front of the advancing injection fluid as is so often claimed. Instead, the fluid tends to 'finger' within the substrate, a process known as 'viscous fingering' (figure , left). The fingers of the injected material form when the fluid takes the lines of least resistance such as the larger pores and cracks. Unfortunately, such pathways are not the most important elements in the conductance of water up the wall. Furthermore, the damper the substrate the greater this fingering is likely to be, especially with solvent based systems since these are not miscible with the resident moisture. Fingering is also increased by injection at high pressure. Reduction of the phenomenon is obtained by low pressure injection or, better still, by gravity diffusion of the DPC fluid. The result of the dampproofing fluids forming fingers give rise to non-impregnated 'pools' within the wall through which water can continue to rise. In the case of pressure injection damp-proof courses, this suggests that it is unlikely that the diffuse band of the damp-proofing agent will be totally

42 complete. The resultant chemical damp-proof course may therefore not stop rising dampness by causing an immediate cut-off of rising water above the damp-proof course like that affected by a physical damp-proof course. Instead, a relatively rapid decline in the moisture gradient should occur above the inserted chemical damp-proof course due to the 'control' exerted. Thus, in practice, the rising ground water should be reduced to such a level that, in association with specialist replastering, it should no longer cause decorative spoiling or damage. The efficacy of the water repellent damp-proofing systems can be affected where there are detergents (surfactants) impregnated into the wall by, for example, past leakage from sink waste pipes. A similar problem may occur when walls are sterilized against dry rot infection by biocide formulations containing surfactants. See fig 13
Fig 13: Distribution of Moisture and salt soluble salts
The overall effectiveness of a remedial damp-proof course can be investigated by examining

43 the relationship between the distribution of free moisture (water due to rising dampness or rising damp figures other source of active water ingress) and contaminant salts (chloride and nitrate). Where rising dampness is still active capillary moisture will be found to the full height of salts (figure, left). The absence of capillary moisture in the presence of salts arising from rising dampness indicates that drying back has occurred (Figure centre) and that the damp-proof course is effective. Intermediary stages are also found which demonstrate different degrees of control of the rising dampness. If chloride and nitrate are not detected in a sampled profile it is possible that the ingress of moisture is due to recently developed rising dampness or more likely through rainwater penetration, condensation, plumbing defect or other sources. When evaluating the efficacy of remedial damp-proof courses care must be taken not to misinterpret electrical moisture meter readings; high readings might not indicate that the damp-proof course itself has failed. They may reflect a number of possibilities including contaminated or inadequate plasterwork. Thus, an accurate assessment of the efficacy of a damp-proof course can only be undertaken by determining full moisture profiles linked with analysis for contaminant salts. It is also important to give consideration to the expected performance and limitations of the installed system as described above. NOTE: It is identified in BS 6576:1985 that where timber suspended floors are encountered the damp-proof course must be injected, where possible, below joist level; this is to protect the embedded timbers from dampness and the risk of fungal decay (fig .
14). However, given the likely efficacy of injection systems the embedded joist ends could still remain in contact with damp masonry even if above the injected damp-proof course and may therefore remain at risk to fungal decay. It would be considered prudent that in all cases where a damp-proof course is installed in relation to a timber suspended floor, action is taken to protect any embedded timbers just above and certainly below the injected damp-

proof course to prevent potential decay!
44
fig 14: Viscous fingering of DPC fluid on injection

45
CHAPTER THREE
RESEARCH METHODOLOGY
3.1 METHODOLOGICAL APPROACH
This method deals with the various methods or sources of data used in obtaining materials and information needed by the researcher for writing the project so as to obtain and achieve meaningful, accurate and correct results in carrying out the research work. The following steps and measures stated below were taken, the process involved the write up practical test being carried out through direct discussion/ interviews, questionnaires of 35 copies were distributed, physical inspection and survey were also carried out on selected houses in both
Rusau and Angwa-Jarawa of Jos North Local Government Area, Plateau State, Jos, in order to assess the use of damp proof course/membrane in the selected residential buildings.
3.2 SOURCES OF DATA
There are two main classifications of sources of data. These are; a) Primary source and b) Secondary sources.
3.2.1 Primary sources
This research employed the use of well structured questionnaire which was developed to collect the required data for the study. Questionnaires are research instruments consisting of series of questions for the purpose of gathering information from respondents. They were sent to professionals within the building industry to find out their opinions about the use of damp proof course during construction of residential buildings.
Interview method was also used in gathering data by one on one conversation. Interview can be personal or through telephone Oasuala (2001) as sited by Umar (2009). An interview is a

46 conversation carried out with definite aim of obtaining certain information. It is a model design to gather information through the responses of the interviewee to the sequence of questions of the researcher.
3.2.2 Secondary sources
This involves the collection of information or data from published or documented materials.
For the purpose of this research, text books, building journals, encyclopaedia, reports, published documents, projects and information obtained from websites such as Google.com,
Ask.com were used but most of all in depth case study was carried out by the researcher within the study area.
3.3 SAMPLE SIZE
This refers to a set of data which consists of all conceivable observation of certain phenomena. The sample size is an important feature of any empirical study in which the goal is to make inferences about a population from a sample. The sample size used in a study is determined based on the expense of data collection, and the need to have sufficient statistical power. Sample size determination is the act of choosing the number of observations or replicates to include in a statistical sample. The need for a sample size is based on fact that a research cannot be carried out covering the entire population of the universe. The sample size for this research study will be selected professionals within the building industry in Jos,
Plateau State. A number of 31 out of 35 questionnaires were issued out to professionals within the building construction industry. In addition, physical survey was carried out by the researcher within the selected settlement that is Rusau and Anwa-Jarawa in Farin-Gada of Jos
North Local Government Area in Plateau State. It a method in which all the buildings within the population of study have equal chance of being selected.

47
3.4 Survey Research
This gives a critical examination of events, objects, subjects or ideas with the intent of providing the exact information about the conditions of situation. The method investigates problems, which are usually viewed with large or vast population sample. If the population is a large one, those to participate in the study are randomly selected, thus, the survey is referred to as sample survey. In a case where the entire population is involved in the investigation, it is called census or universal survey. The survey under investigation has direct influence on the variables involved.
Survey research can be qualitative or quantitative in character. Qualitative are based on the researcher’s opinion that is it is subjective.
3.5 Methods of data collection and their justifications
The data used in this research work were collected by hand. The questionnaire was distributed and collected back by hand. Most of the questions were answered before the researcher within the area of study.
Analysis of data is a process of inspecting, transforming and modelling data with the goal of making useful information, suggesting conclusions and supporting decision making. The data from the questionnaire were presented in the form of table while bar and pie charts were used for the purpose of analysis. The methods used as stated earlier were primary method that is the use of questionnaire. Questionnaires were used as a means of data collection because of its advantage of assessing confidential information which the researcher ordinarily cannot have access to it. The questionnaire has the advantage of finding out different opinions from people with or no bias.

48
Various statistical methods were used in the analysis of the data. The statistical analyses used include; a) Simple percentage b) Likert Summating rating scales c) Tables, Bar and pie charts
3.5.1 Simple percentage
This is used to find out the number of respondents agreeing with a particular option on the questionnaire as compared with the total number of respondents who answered or responded to that particular option indicating the number of respondents in percentage. The simple percentage is calculated using the formula: 𝑥 𝑛
𝑋100
Where x=number of observation (respondents) in each question
N=total number of observation in each question
3.5.2 Likert Summating rating scale
This is a kind of rating scale used for the treatment of sensitive questions with listed variables. The Likert summating scales- Strongly Agreed (SA), Agreed (A), Undecided (U) or neutral, Disagreed (D), and Strongly Disagree (SD). It is rated with 5,4,3,2,1 respectively.

49
3.5.3 Bar and Pie charts
The bar charts consist of rectangles with bases on the x-axis and the areas of the rectangles are proportional to the corresponding class frequencies. Each rectangle is separated from each adjacent rectangle by equal intervals. The essential features about a bar chart are that the mid- points of the bases of each bar are marked, and each block or bar is closed, thus leaving no room for uncompleted rectangles. The pie chart is a display diagram which represents the quantity or volume of data in sectors of a handful of items. When eight or more items are represented in pie charts, the charts will have too many sectors and resulting visual picture loses its usefulness. Ideally, a good pie chart should consist of about four to six sectors.

50
CHAPTER FOUR
DATA PRESENTATION, ANALYSIS AND DISCUSSION
4.1 General Information of respondents
Results from table 1 indicates that 61% responded to section A. Thus, 21 (68%) have qualification in B.Sc, B. Tech, B.Eng (Building), 8 (26%) are HND holders, 10% are
M.Sc holders.
Table 1 shows the qualification of respondents.
S/No Qualification
1. B.Sc., B.Tech., B.Eng
Number
21
Percentage (%)
68
2.
3.
HND
M.Sc
8
2
31 Total
Source: Research questionnaire (2014)
26
6
100

51
Table 2 shows that 12(39%) have less than 5 years of experience, 10(32%) have 5-10 years of experience, 5(16%) have 10-15 years of experience, 4(13%) have 15-20 experience.
None has above 20 years of experience.
Table 2 represents the years of experience of respondents in the building industry.
S/No Years of experience Number Percentage (%)
1. Less than 5-years 12 39
2.
3.
5 years- 10 years
10 years- 15 years
10
5
32
16
4.
5.
15 years- 20 years
20 years and above
4
0
31 Total
Source: Research Questionnaire (2014)
13
0
100

52
4.2.1
Respondents’ opinion about DPC/DPM.
The second section is designed to inquire of the respondents their general views and opinion of the use, its effect, challenges and importance on the use of DPC/DPM.
Table 3 represents the frequency of houses developed by respondents.
Class boundary
1-10
11-20
Frequency
20
11
∑= 31
Source: Research questionnaire (2014)
Percentage (%)
65
35
100

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From table 3 the results, a total number of 54-bungalow residential buildings were surveyed.
19% were observed to have been constructed with DPC/DPM. While 82% were observed not to have been constructed with DPC/DPM. 67% of 2-floor high rise residential buildings were constructed with DPC/DPM, while 33% were not constructed with it. The table below represents the results of the physical survey.
Table 3: shows the use of DPC in residential building
Type of No_ With Percentage Without building Surveyed DPC/DPM % DPC/DPM
Bungalow
Duplex
54
1
10
1
19
100
44
0
1-floor
2-floors
3-floors
2
3
-
2
2
-
100
67
-
0
1
-
Percentage
%
81
-
-
33
-
Source: physical Survey carried out by the researcher (2014)

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Table 4 seeks to find out why developers don’t use DPC/DPM as recommended/ specified in drawings. Various reasons were responded to. From the results, it shows that lack of funds ranks highest with 11 respondents indicating 35%, unavailability of materials and time constraints ranks second with 7 respondents, indicating 23% respectively, while 6 respondents indicating 19% ranks third.
Table 4; challenges to the use of DPC/DPM
S/No Reasons for not using DPC/DPM as recommended
Number of respondents
Percentage (%)
1. Due to ignorance 0 0
2. Due to lack of funds
3. Unavailability of materials
4. Materials used are less effective for intended 6 use
5. Due to time constraints 7
11
7
Total
Source: Research questionnaire (2014)
31
35
23
19
23
100

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Table 5 seeks to assess the resultant effect of not using DPC/DPM. From the responses it shows that rise in water level visibly seen on the wall ranks highest with 31 responses indicating 100%, deterioration of paints on walls is second with 29 responses indicating 94%, and presence of humidity in building ranks third with 27 response indicating 87%.
Table 5; Resultant effects of not using DPC/DPM
S/No Resultant effects of not using
DPC/DPM
SD D N A SA
1. Rise in water level visibly seen on the 0 0 0 3 28 wall (10%) (90%)
2. Deterioration of paints on walls 0 1 0
(3%)
11 18
(36%) (58%)
3.
4.
Presence of humidity in buildings
Growth of mold and rot on wall
0 3 1 18 9
(10%) (3%) (58%) (29%)
0 1 3 20 7
(10%) (10%) (65%) (23%)
5. When the health of occupants are 3 threatened by its effects (10%)
8 10
(26%) (32%)
7 3
(23%) (10%)
6. When thermal insulation of building 2 materials are affected (6%)
5 7 9 8
(16%) (23%) (29%) (26%)
Source: Research questionnaire (2014)
Table 6 shows the benefits of the use of DPC/DPM. From the table it shows that prevention of water from entering the wall ranks highest with 30 responses indicating 97%, prevention

56 of condensation, prevention of health such as asthma challenges are ranked next with 29 responses indicating 93%, and making the dry for occupants, reduction in cost trying to rectify the problem ranked third with 27 indicating 87% each. The table below shows the above analysis.
Table 6; Benefits of using DPC/DPM in residential building
S/No Benefits of use of DPC/DPM
1. It gives the building its life span expectancy
SD
8
D
6
N
1
(27%) (19%) (3%)
A
10
SA
6
(32%) (19%)
2. It prevents deterioration of walls, 3 paints, decoration. (10%)
5
(16%)
2
(7%)
10 11
(32%) (36%)
3. It reduces the cost of trying to rectify 2 the problem. (5%)
1
(3%)
1
(3%)
13 14
(42%) (45%)
4. It gives the occupants comfort by 1 making the room dry to live in. (3%)
2
(7%)
1
(3%)
18 9
(58%) (29%)
5. It prevents water from entering the 0 1 walls. (3%)
0 9 21
(29%) (68%)
6. It prevents condensation 0 2
(6%)
0 10
(32%)
19
(61%)
7. It prevents health challenge such as 1 asthma (3%)
3 1
(10%) (3%)
15 12
(48%) (39%)
Source: Research questionnaire (2014)

57
Table 7 addresses the major challenges of the use of DPC/DPM in residential buildings. From the responses it shows that 30 respondents disagree with ignorance as a challenge with 30 responses indicating 97%, 24 respondents agree that lack of experience in its installation is a challenge indicating 77%, and 20 respondents disagree that clients oppose to its use indicating 65%.
Table 7; Challenges of not implementing DPC/DPM in residential building
S/No Challenges of not using DPC/DPM SD D N A
1. It is expensive to purchase 8 10 0 8
(26%) (32%)
SA
5
(26%) (16%)
2. It is due to ignorance 19 11
(61%) (36%)
0 1
(3%)
0
3. Its time consuming
4. Lack of experience in installing it.
10 8
(32%) (26%)
0 1
(3%)
0
3 2 2 18 6
(10%) (6%) (6%) (58%) (19%)
5. Non- availability of DPC/DPM materials 6 9 1 8 7
(19%) (29%) (3%) (26%) (23%)
6. Clients oppose to its use during 13 construction.
7
(42%)
(23%)
0 5
(16%)
6
(19%)
Source: Research questionnaire (2014)

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CHAPTER FIVE
SUMMARY OF FINDINGS, CONCLUSION AND RECOMMENDATIONS
5.1 SUMMARY OF RESULTS
The highlights of the findings are summarized as follows;
1) From the results, a total number of 54-bungalow residential buildings were surveyed.
10 residential buildings indicating 19% were observed to have been constructed with
DPC/DPM, while 44 residential buildings indicating 82% were observed not to have been constructed with DPC/DPM. 2 residential buildings indicating 67% of 2-floor high rise residential buildings were constructed with DPC/DPM, while 1 residential building representing 33% was not constructed with DPC.
2) From the results, it shows that prevention of water from entering the wall ranks highest with 30 responses indicating 97%, prevention of condensation, prevention of health such as asthma challenges are ranked next with 29 responses indicating 93%, and making the room dry for occupants, reduction in cost trying to rectify the problem ranked third with 27 indicating 87% each.
3) From the results about the use of DPC/DPM, it shows that lack of funds ranks highest with 11 respondents indicating 35%, unavailability of materials and time constraints ranks second with 7 respondents, indicating 23% respectively, while materials used are less effective for intended use ranks third with 6 respondents indicating 19%.
4) The resultant effect of not using DPC/DPM from the responses, shows that rise in water level visibly seen on the wall ranks highest with 31 responses indicating 100%, deterioration of paints on walls is second with 29 responses indicating 94%, and presence of humidity in building ranks third with 27 response indicating 87%.

59
5) The results show that 24 respondents agree that lack of experience in the installation of DPC/DPM is a challenge indicating 77%.
6) Considering the benefits of the use of DPC/DPM, the results shows that prevention of water from entering the wall ranks highest with 30 responses indicating 97%, prevention of condensation, prevention of health such as asthma challenges are ranked next with 29 responses indicating 93%, and making the dry for occupants, reduction in cost trying to rectify the problem ranked third with 27 indicating 87% each.
5.2 CONCLUSION
From the results, it shows that these professionals in the building industry have knowledge about DPC/DPM and its effects on residential buildings if used or neglected. The research has shown that, some professionals don’t make use of it when constructing residential building as recommended largely due to lack of funds which tops the chart of reasons why it is not used, followed by unavailability of materials and time constraints ranking same. The research reveals that lack of use of DPC/DPM in any kind of residential building is unhealthy to the structure and the occupants.
The research also reveals that, the following when it occurs in a residential building, is an indication of lack of use of DPC/DPM; a) Rise in water level visibly seen on the wall, b) Deterioration of paints and decoration on walls, c) The presence of humidity in the building, d) Growth of mould and rot on wall,

60 e) When the health of occupants are threatened with symptoms caused by mould allergy which may include respiratory illness or asthma watery, itchy, red eyes;
Chronic cough; Headaches or migraines; Rashes (dermatitis); Tiredness; Sinus problems, blocked nose; (New York City, 2000). f) When the thermal insulation of the building materials are affected.
The research also shows that there are challenges associated with using DPC/DPM in residential buildings. These are; a) It is very expensive when considering using quality material and technique. b) Its time consuming, c) Some of the professionals lack requisite knowledge about its installation, d) Non-availability of DPC materials.
5.3 RECOMMENDATION
There should be enforcement of building regulations.
There should be thorough and intensified site investigation to ensure compliance with standards especially as regards the use of DPC/DPM.
High quality DPC/DPM materials that meet British Standards, and other building accreditations, should be used as it is simply not worth the risk of using lower grade product for these essential functions.
Professionals should integrate the cost of installing DPC/DPM in their bill of quantities
(BOQ) and faithfully ensure that quality materials are used for the installation.

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Within the building industry, there should be provision for training adequately professionals/experts on how to install DPC material and how to solve the problem by a way of remedial measure when called upon to remedy an existing effect of lack of use of
DPC/DPM in a residential building.
Occupants of residential buildings being affected by dampness, should constantly avoid steaming in the rooms, allow proper ventilation, clean up bathrooms frequently, the use of exhaust fans should be encouraged.