Specification for:
Two storey side and single storey side extension, loft
conversion including gable extensions to roof and
insertion of rear dormers
48 Denham Way
Maple Cross
WD3 9SP
Revision: A
1.0 PREMINARIES
1.01 The whole of the work to be in full accordance with the current building Regulations
whether or not defined in this specification or accompanying drawings, and to be to the
satisfaction of the local authority.
1.02 No part of the work to project beyond the boundary unless agreed with the adjoining owner.
All dimensions to be checked on site
1.03 The party wall etc act 1996 is not part of these details and the building owner should be
aware that agreements may have to be entered into with the adjoining owner {so where
applicable}
1.04 Glazing to doors and side panels within 300mm to doors to a height of 1500mm, and
windows below 800mm in height to have safety glass toughen or laminated in accordance with
BS 6206: 1981. All glazing to be double glazed with 16 mm air gap and low-E coating inner pane
.{or 12 mm gap and argon filled}.All incorporating thermal draughts seals. Windows to have 1.8
U values.
Access to main entrance doors to have 900mm clear openings for disabled access.
1.05 Emergency escape windows to be provided to new habitable rooms having a clear opening
450MM X 750MM {0.33M2}. Cill height to be max 1.1M min 0.8m
1.06 SMOKE DETECTION Mains operated linked smoke alarm detection system to BS 5446 1:2000 and BS5839-6:2004 to at least a Grade D category LD3 standard and to be mains powered
with battery back up. Smoke alarms should be sited so that there is a smoke alarm in the
circulation space on all levels/ storeys and within 7.5m of the door to every habitable room. If
ceiling mounted they should be 300mm from the walls and light fittings. Where the kitchen area
is not separated from the stairway or circulation space by a door, there should be an interlinked
heat detector in the kitchen..
1.07 All electrical switches, socket outlets, TV and telephone points inhabitable rooms to be fixed
between 450mm and 1200mm above finished floor level. 1no energy saving type lamp
{40Lum/CIRCUIT/watts} for 1-3 rooms created
1.08 These specification notes are to be read in conjunction with the following drawings and the
structural engineers' details and or calculations. Plan No: POt/2016/001/A
If any of the above information is not attracted to this specification it is Responsibility of the
builder to inform the designer or client prior to Commencing work on site.
1.09 All dimensions are in millimetre's {mm} and are to be checked by builder at setting out
stage. DOES NOT SCALE FROM DRAWING, IF IN DOUBT ASK?
1.10 All works and materials are to comply with current building regulations, codes of practice
and British standards.
1.11 Prior to commencing work, builder to confirm with designer that the structural engineers
comments and building control, approval have been received. Where work commences prior to
receipt above , it is responsible of the builder of advice that client and designer cannot be held
responsible for any alterations required by the building control {or structural engineer}nor can
the designer be held responsible for any costs thereby incurred {by builder or client}
1.12 It is the contractual responsibility to ensure that all dimensions noted on the plans for
contractual purposes are accurate NO MATERIALS OR MONIES SHOULD BE EXPANDED
UNTIL THE CONTRACTOR IS SATISFIED THAT THE PLANS HAVE NO
DISCREPENCIES. For example, the internal height of loft conversions should be checked and
the client informed of the internal room height to be achieved before ordering any materials or
expanding monies the client agreements in writing will need to be obtained by the contractor if
there is any discrepancy between site issues and plans then the designer should be informed
immediately.
1.13 All electrical work required to meet the requirements of Part P (Electrical Safety) must be
designed, installed, inspected and tested by a person competent to do so. Prior to completion the
council should be satisfied that part P has been complied with. This may require an appropriate
BS 7671 electrical installation certificate to be issued for the work by a person competent to do
so.
1.14 Provide cavity trays and code 4 lead flashings at all wall/roof abutments {lead to be laid in
accordance with LDA guidance}.Use retro fit cavity trays where requested by BCO.
All new timber to be c16 not sc3 unless stated on Drawings.
2.00 THERMAL BRIDGING
2.01 Care shall be taken to limit the occurrence of thermal bridging in the insulation layers caused
by gaps within the thermal element (i.e. around windows and door openings).
3.00 EXISTING STRUCTURE
3.01 Existing structure including foundations, floor, beams, walls, roof and lintels are to be
exposed and checked for adequacy prior to commencement of work and as required by the
Building Control Officer. Particular care must be taken if the existing external wall is single leaf
construction with piers, checks for stability and defects must be performed.
8.00 PITCHED ROOF
(imposed load max 0.75 kN/m² - dead load max 0.75 kN/m²)
Vented roof – pitch 22-45°
To achieve U-value 0.18 W/m²K
8.01 Existing roof structure to be assessed by a structural engineer and any alterations to be carried
out in strict accordance with structural engineer’s details and calculations which must be approved by
building control before works commence on site.
8.02 Roof construction – As per drawing, rafters at max 400mm centres span to engineer's details.
Insulation to be 100mm Celotex GA4000 between rafters between and 52mm Celotex PL4000
insulated plasterboard under rafters.
8.03 Maintain a 50mm air gap above insulation to ventilate roof. Provide opening at eaves level at
least equal to continuous strip 25mm wide and opening at ridge equal to continuous strip 5mm wide to
promote ventilation or provide equivalent high and low level tile vents in accordance with
manufactures details. Finish with 5mm skim coat of finishing plaster to the underside of all ceilings
using galvanized plasterboard nails.
8.04 INSULATION AT CEILING LEVEL
To achieve U value of 0.16 W/m²K
8.06 Insulation at ceiling level to be 100mm Rockwool insulation laid between ceiling joists.
8.07 Construct ceiling using sw joists at 400mm centres, finished internally with 12.5mm plasterboard
and min 3mm thistle multi-finish plaster. Provide polythene vapour barrier between insulation and
plasterboard. Provide opening at eaves level at least equal to continuous strip 25mm wide in two
opposite sides to promote cross ventilation. Allow for all structure as designed by a Structural
Engineer.
9.00 INTERNAL STUD PARTITIONS
9.01 100mm x 50mm softwood treated timbers studs at 400mm cts with 50 x 100mm head and
sole plates and solid intermediate horizontal noggins at 1/3 height or 450mm. Provide min
10kg/m² density acoustic soundproof quilt tightly packed (eg:100mm Rockwool or Isowool
mineral fibre sound insulation) in all voids the full depth of the stud. Partitions built off doubled
up joists where partitions run parallel or provide noggins where at right angles (if required).
Walls faced throughout with 12.5mm plaster board with skim plaster finish. Taped and jointed
complete with beads and stops.
9.02 Fix 12.5mm Fireline plasterboard to the outer face of the stud wall. All junctions to have
water tight construction, seal all perimeter joints with tape internally and with silicon sealant
externally. Note: These walls need to go full height and be fire stopped against the roof or floor
above. A lesser provision of insulation may be appropriate where meeting such a standard would
result in a reduction of more than 5% in the internal floor area of the room.
10.00 upper floors
10.01 floor to be constructed of 21mm t & g flooring grade chipboard on joists at 400mm
Centres in accordance with current Trada Tables . 100mm mineral wool
Insulation between joists 15kg/ms.
10.02 joists to bear on ms joists hangers. (hangers to be restraint type hangers).
10.03 joists to restrain walls with ms anchors (30mm x 5mm) and positioned at 2000mm Centers.
10.04 ceiling to be clad with 12.7mm plasterboard and skim.
10.05 underside of floor exposed to external air to be clad with 9mm`masterboard` Or equal with
cover strips at butt joists. Insulation laid between the joists to be 100mm Rockwool insulation.
10.06 Floor covering in bathroom, kitchen and wet areas to be flooring grade plywood and
screwed Down.
10.07 joists hangers at existing wall end may be fixed to face of wall plate (same size as joists)
which has been fixed to wall with 9mm expanding anchor bolts at 600mm centers in staggered
form.
10.08 joists that have span greater than 2500mm to have mid span solid bridging.
10.09 all timbers trimming chimney breast and stack to have 50mm gap if chimney is In use
10.10 floor joists to be as shown at 400mm centers.
11.00 BACKGROUND AND PURGE VENTILATION
11.01 Background ventilation - Controllable background ventilation via trickle vents to BS EN
13141-3 within the window frame to be provided to new habitable rooms at a rate of min
5000mm²; and to kitchens, bathrooms, WCs and utility rooms at a rate of 2500mm²
11.02 Purge ventilation - New windows/rooflights to have openable area in excess of 1/20th of
the floor area if the window opens more than 30°, or 1/10th of the floor area if the window opens
less than 30°.
11.03 Internal doors should be provided with a 10mm gap below the door to aid air circulation.
11.04 Ventilation provision in accordance with the Domestic ventilation compliance guide.
12.00 NEW AND REPLACEMENT WINDOWS
To achieve U-value of 1.6 W/m²K
12.01 New and replacement windows to be draught stripped and double glazed with 16mm argon
gap and soft coat low-E glass. Window Energy Rating to be Band C or better. The door and
window openings should be limited to 25% of the extension floor area plus the area of any
existing openings covered by the extension. Windows in a cavity wall to have insulated damp
proof course around opening. Windows in a solid wall to have insulated dry lining around the
opening.
13.00 ESCAPE WINDOWS
13.01 Provide emergency egress windows to any newly created first floor habitable rooms and
ground floor inner rooms. Windows to have an unobstructed openable area of 450mm high x
450mm wide, minimum 0.33m sq, the bottom of the openable area should be not more than
1100mm above the floor. The window should enable the person to reach a place free from danger
from fire.
14.00 NEW AND REPLACEMENT DOORS
15.00 INTERNAL LIGHTING
15.01 Install low energy light fittings that only take lamps having a luminous efficiency greater
than 45 lumens per circuit watt and a total output greater than 400 lamp lumens. Not less than
three energy efficient light fittings per four of all the light fittings in the main dwelling spaces to
comply with Part L of the current Building Regulations.
16.00 external walls - cavity {traditional}
16.03 brickwork/block work above DPC to be bedded in 1:5 mortar mix with plasticizer
addictive.
17.01 Stairs intended to be used for only one dwelling with a maximum rise of 220mm and a
minimum going of 220mm. A maximum pitch of 42° is stipulated for domestic stairs. A Stair
width between 800mm and 900mm
17.02 The normal relationship between the dimensions of the rise and going can be expressed as
detailed in Approved Document K, which states that twice the rise plus the going (2R+G) should
be between 550mm and 700mm.
17.03 The angle between the pitch line (notional line connecting nosings) and the horizontal. The
maximum pitch for domestic stairs is 42°. A headroom of 2m clear is adequate on the access
between levels.
17.04 Height of handrails in accordance with Approved Document K, the flights to have a
handrail on at least one side if they are less than one metre wide and on both sides if they are
wider than one metre. There is no need for handrails beside the bottom two steps of a stairway.
Minimum domestic handrail heights of 900mm for both stairs and landings, public handrail
heights should be a minimum of 900mm on stairs and 1100mm on landings. No openings in any
balustrading should allow the passage of a 100mm sphere.
17.05 Landings to be clear of permanent obstruction. Any doors across landings will have a clear
space of at least 400mm across the full width of flight.
18.00 Ventilation
18.01 ventilation to habitable rooms, and w.c to be not less than 1/20th of the floor area and shall
be provided by opening windows lights.
18.02 EXTRACT TO W/C
W/C to have mechanical ventilation ducted to external air with an extract rating of 15l/s operated
via the light switch, to have a 15min overrun if no window in room. Internal doors should be
provided with a 10mm gap below the door to aid air circulation. Ventilation provision in
accordance with the Domestic ventilation compliance guide. Intermittent extract fans to BS EN
13141-4. All fixed mechanical ventilation systems, where they can be tested and adjusted, shall
be commissioned and a commissioning notice given to the Building Control Body.
18.03 EXTRACT TO BATHROOM
Bathroom to have mechanical vent ducted to external air to provide min 15 litres / sec extraction.
Vent to be connected to light switch and to have 15 minute over run if no window in room.
Internal doors should be provided with a 10mm gap below the door to aid air circulation.
Ventilation provision in accordance with the Domestic ventilation compliance guide. Intermittent
extract fans to BS EN 13141-4. All fixed mechanical ventilation systems, where they can be
tested and adjusted, shall be commissioned and a commissioning notice given to the Building
Control Body.
18.06 BACKGROUND AND PURGE VENTILATION
Background ventilation - Controllable background ventilation via trickle vents to BS EN 13141-3
within the window frame to be provided to new habitable rooms at a rate of min 5000mm²; and to
kitchens, bathrooms, WCs and utility rooms at a rate of 2500mm²
Purge ventilation - New Windows/rooflights to have openable area in excess of 1/20th of their
floor area, if the window opens more than 30° or 1/10th of their floor area if the window opens
less than 30°
Internal doors should be provided with a 10mm gap below the door to aid air circulation.
Ventilation provision in accordance with the Domestic ventilation compliance guide.
19.00 plumbing
19.01 SVP pipe to be 100mm UPVC and to terminate 900mm above window heads and to be
fitted with a durable guard.
19.02 no connection to be made to SVP within 200mm below .W.C junction.
19.03 all waste pipes to be ABS and fitments to have 75mm deep seal traps. Sink bath, Shower
and bidet to have 38mm minimum waste. Basin to have 32mm minimum waste
19.04 Roding eye to be provided at junctions and bends with clearing eyes, where SVP connects
to ground drainage allow rodding eye 900mm from floor level.
19.05 over flow from WWP to discharge through external wall.
19.06 all pluming to be in accordance with BS 5572.
19.07 all waste pipes penetrating floors and to be sealed around aperture Within tumescent foam,
and boxed around with 12.5mm plasterboard And skim.
19.09 provide radiators located in accordance with the clients instructions to heating Contractors
design with TRV on new.
19.10 contractor to fully allow to install all bathrooms, kitchen units tilling etc in accordance
With the clients instructions.
19.11 Inline bleeding will be used on baths to limit water temperature to 48 deg.C. and prevent
scalding.
19.12 The Consumption of Wholesome water for new dwellings not to be more than 125/l/h/d
20.00 Drainage
20.02 UNDERGROUND FOUL DRAINAGE
Underground drainage to consist of 100mm diameter UPVC proprietary pipe work to give a 1:40
fall. Surround pipes in 400mm pea shingle (900mm under drives). Shallow pipes to be covered
with 100mm reinforced concrete slab over compressible material. Provide rodding access at all
changes of direction and junctions. All below ground drainage to comply with BS7158 and
BS801.
20.03 INSPECTION CHAMBERS
Underground quality proprietary UPVC 450mm diameter inspection chambers to be provided at
all changes of level, direction, connections and every 45m in straight runs. Inspection chambers
to have bolt down double sealed covers in buildings and be adequate for vehicle loads in
driveways. 20.04 all new drainage to be 100mm upvc encased in pea shingle and laid to 1:40 Fall.
20.05 ABOVE GROUND DRAINAGE
Above ground drainage to comply with BS.5572.1978 for sanitary pipework. All drainage in
accordance with part H of the Building Regulations. Wastes to have 75mm deep anti vac bottle
traps and rodding eyes at changes of direction. All plumbing to be to BS 5572.
Size of wastes pipes and max length of branch connections (if max length is exceeded then anti
vacuum traps to be used)
Sinks - 3m for 40mm pipe 4m for 50mm pipe
Washing machine and dishwasher - stand pipe 50mm
Wash basin - 1.7m for 32mm pipe 4m for 40mm pipe
Bath/shower - 3m for 40mm pipe 4m for 50mm pipe
W/c - 6m for 100mm pipe for single wc
All branch pipes to connect to 110mm soil and vent pipe. Waste pipes not to connect within
200mm of the wc connection.
Supply hot and cold water to all fittings as appropriate.
20.06 SOIL AND VENT PIPE
Svp to be extended up in 110mm dia UPVC and to terminate min 900mm above any openings
within 3m. Provide a long radius bend at foot of SVP. connections and every 45m in straight
runs. Inspection chambers to have bolt down double sealed covers in buildings fully accessible
and be adequate for vehicle loads in driveways.
20.08 AUTOMATIC AIR VALVE
Ground floor fittings from wc to be connected to new 110mm UPVC soil pipe with accessible
internal air admittance valve complying with pr EN 12380, placed at a height so that the outlet is
above the trap of the highest fitting and connected to underground quality drainage encased with
pea gravel to a depth of 150mm
20.09 RAINWATER DRAINAGE
New rainwater goods to be new 110mm UPVC half round gutters taken and connected into
68mm dia UPVC downpipes. Rainwater taken to new soakaway, situated a min distance of 5.0m
away from any building, via 110mm dia UPVC pipes surrounded in 150mm granular fill.
Soakaway to be min of 1 cubic metre capacity for every 16.5m2 of roof area drained in clay soils.
(or to depth to Local Authorities approval) with suitable granular fill with geotextile surround to
prevent migration of fines. If necessary carry out a porosity test to determine design and depth of
soakaway.
20.10 PIPEWORK THROUGH WALLS
Where new pipework passes through external walls form rocker joints either side wall face of
max length 600mm with flexible joints with short length of pipe bedded in wall.
Alternatively provide 75mm deep pre-cast concrete plank lintels over drain to form opening in
wall to give 50mm space all round pipe: mask opening both sides with rigid sheet material and
compressible sealant to prevent entry of fill or vermin.
21.00 Steelwork
21.01 All steelwork fabrication & erection to be in accordance with BS5950.
21.02 All structural mild steel to be grade S275 unless noted otherwise.
21.03 All structural steelwork including bolts, cleats etc. to be supplied by the steelwork
Contractor.
21.04 All nuts, bolts and washers to be a grade 8.8 complying with BS4190 and BS4320.
Minimum size of bolts to be M20 diameter, unless noted otherwise.
21.05 All welds to be 6mm continuous fillet weld unless noted otherwise.
21.06 All plates to be 15mm thick unless noted otherwise.
21.07 All members to have a minimum two bolt connections. All beams to have a minimum four
bolt connections.
21.08 All structural steelwork to be shot blasted to remove all loose mill scale, rust etc. and
painted with one intumescent paint, fire line plasterboard or 2 layers of standard plasterboard..
21.09 All structural steelwork below ground level to have minimum 100 mm concrete surround
and to have r/w coating
22.00 NEW STAIRCASE
22.01 Dimensions to be checked and measured on site prior to fabrication of stairs. Timber stairs to
comply with BS585 and with Part K of the Building Regulations. Max rise 220mm, min going
220mm. Two risers plus one going should be between 550 and 700mm.
22.02 Tapered treads to have going in centre of tread at least the same as the going on the straight.
Min 50mm going of tapered treads measured at narrow end.
22.03 Pitch not to exceed 42 degrees. The width and length of every landing should be at least as great
as the smallest width of the flight.
22.04 Doors which swing across a landing at the bottom of a flight should leave a clear space of at
least 400mm across the full width of the flight. Min 2.0m headroom measured vertically above pitch
line of stairs and landings.
22.05 However, if there is not enough space to achieve this height the headroom will be satisfactory if
the height measured at the center of the stair width is l.9 m reducing to 1.8m at one side of the stair.
Handrail on staircase to be 900mm above the pitch line,
23.00 MEANS OF ESCAPE - Door upgrade
23.01 Form a protected escape stairway by providing half hour fire resistance to all partitions as well
as floors and ceilings above and below rooms.
23.02 Stairway to be protected at all levels - from the loft room/rooms then leading directly to an
external door at ground level (no inner rooms allowed).
23.03 Existing Doors on to protected route to be upgraded with proprietary intumescent paint/paper
products with relevant BBA certificate applied as manufacturer's details to achieve 30 minutes fire
resistance (check suitability of doors as agreed with building control before works commence on site).
24.00 PITCHED ROOF
(imposed load max 0.75 kN/m² - dead load max 0.75 kN/m²)
Vented roof – pitch 22-45°
To achieve U-value 0.18 W/m²K
24.01 Existing roof structure to be assessed by a structural engineer and any alterations to be carried
out in strict accordance with structural engineer’s details and calculations which must be approved by
building control before works commence on site.
24.02 Roof construction - 50 x 200 mm Grade C24 rafters at max 400mm centres span to engineer's
details. Insulation to be 100mm Celotex GA4000 between rafters between and 52mm Celotex PL4000
insulated plasterboard under rafters.
24.03 Maintain a 50mm air gap above insulation to ventilate roof. Provide opening at eaves level at
least equal to continuous strip 25mm wide and opening at ridge equal to continuous strip 5mm wide to
promote ventilation or provide equivalent high and low level tile vents in accordance with
manufactures details. Finish with 5mm skim coat of finishing plaster to the underside of all ceilings
using galvanized plasterboard nails.
24.04 INSULATION AT CEILING LEVEL
To achieve U value of 0.16 W/m²K
24.06 Insulation at ceiling level to be 100mm Rockwool insulation laid between ceiling joists.
24.07 Construct ceiling using sw joists at 400mm centres, finished internally with 12.5mm
plasterboard and min 3mm thistle multi-finish plaster. Provide polythene vapour barrier between
insulation and plasterboard. Provide opening at eaves level at least equal to continuous strip 25mm
wide in two opposite sides to promote cross ventilation. Allow for all structure as designed by a
Structural Engineer.