Elements of a Structure

Element 4 Part 1
Issue Oct 2011
Fire Protection in Buildings
Building Regulations 2000
• In general covers new builds and modifications
• Schedules A-K contain information on structures, fire,
moisture, toxic substances, noise, ventilation, hygiene and
Part B (Fire Safety) of the Building
Regulations and Approved Document B
Volume 1 - Dwellinghouses
Volume 2 – Buildings Other Than
Flats (including multi-storey flats &
mixed-use buildings) can be found in
Volume 2
Part B (Fire Safety) of the Building
Regulations and Approved Document B
Schedule B Fire
B1 Means of warning and escape
B2 Internal fire spread (linings)
B3 Internal fire spread (structure)
B4 External fire spread
B5 Access facilities for the fire service
Appendices regarding fire performance materials with
regards test methods
Fire Resistant Properties
Common Building Materials
Resistance to collapse Load Bearing
Fire & Smoke Penetration Integrity
Transfer of Excessive Heat Insulation
Resistance of Fire Doors Stop the spread
of smoke, fumes or heat.
Elements of a Structure
• a. A member forming part of a structural frame of a
building or any other beam or column
• b. A load bearing wall or load bearing part of a wall
• c. A floor
• d. A gallery
• e. An external wall
• f. A compartment wall
Timber burns at the surface
Does not expand when heated
Does not collapse suddenly
Fire resistance depends on:  Thickness & cross sectional area
 Tightness of joints
 Type of wood
 Treatment
Reinforced Concrete Frames
 Types: - Reinforced, Pre-stressed (pre
& post tensioned)
 Resistant to fire
 Fire resistance depends on type &
thickness of concrete used & protection
afforded by the concrete to the steel
Brickwork & Blockwork
• Resistant to fire
• Resistance depends on: Thickness
Plastering or coating
Whether load bearing or not
Cavities within the bricks or blocks
Structural Steel
 Non-combustible
 Steel expansion causes buckling can affect
stability of building
 Steel looses strength in a fire
Sheet Materials
• Fibre board can be fire resistant if
• Plaster boards retard fire spread
• Plywood/chipboard depends on
properties of wood
• Plastic has little fire resistance
• Glass breaks unless wired or tempered
Lining Materials
• Mostly non-combustible
• Some older types may contain wood
• Plaster (calcium hydroxide) has good
fire resistance
B2 Internal Fire Spread (linings)
• To inhibit the spread of fire within the
building the internal linings shall resist the
spread of flame over their surfaces and if
ignited a rate of heat release or a rate of
fire growth which is reasonable in the
B3 Internal Fire Spread (structure)
• The building shall be designed and
constructed so that in the event of fire, its
stability will be maintained for a reasonably
Concealed spaces (cavities)
Protection of openings and fire stopping
•To prevent fire, heat, and smoke from spreading beyond locations of origination
•Building elements such as fire walls, fire dampers, and fire doors, are designed
to seal off one location from the next.
•Increases the safety by allowing evacuating building occupants because smoke
and fire are not able to escape into exit passageways.
•Containment of fire and smoke reduces property damage and prevents small
fires from growing.
•In order for compartmentation efforts to be effective
fire barriers must be maintained
• 30 min fire resistance
• Maintains building
• Allows sufficient time to
• Minimises destruction
• Assists firefighting
To prevent fire, heat, and smoke from spreading
beyond locations of origination.
Cavity Barriers
Compartment Walls/ Floors Junction
Openings & Voids
• These can eliminate the protection afforded by
the compartment
• Any opening will allow fire to spread quickly
• Voids eg cable ducts, suspended ceilings &
floors provide ready routes for fire spread
• “Fire Stopping” ensures barriers to fire spread
are replaced
B4 External Fire Spread
• The external walls of the building shall
adequately resist the spread of fire over the
walls and from one building to another, having
regard to the height, use and position of the
• The roof of the building shall adequately resist
the spread of fire over the roof, from one
building to another, having regard to the use
and position of the building.
B1 Means of warning and escape
• The building shall be designed and
constructed so that there are
appropriate provisions for the early
warning of fire, and appropriate
means of escape (MOE) in case of
fire from the building to a place of
safety and effectively used at all
B1 Means of warning and escape
• B1 will be met if:
• There are routes of sufficient numbers and
capacity which are suitably located
• The routes are sufficiently protected from the
effects of fire by enclosure where necessary
• Routes are adequately lit and sign posted
• Appropriate facilities to either limit the ingress of
smoke to the escape routes or to restrict the fire
and remove the smoke
• Arrangements for early warning
• Protection of escape routes
Means Of Escape
“Structural means forming an integral part of the
building whereby persons can escape from fire
by their own unaided efforts to a place of safety”
– Consider – structure, travel, fire, place of
– Main principles BS5588 and Acop’s and The
Building Regulations 2000
Strategic Factors Affecting Means
Of Escape
Time of evacuation
Travel Distance
Maximum Travel Distances
Where more than one route is available
• 25 m – high risk area
• 45 m – normal risk area
• 60 m – low risk area
Where only single escape route is available
• 12 m – high risk area
• 25 m – normal risk area
• 45 m – low risk area
Escape Routes
• Stairways, corridors and areas near the fire exits
should be kept clear of obstructions and material
which can catch fire.
• The escape route should lead to a final exit and a
safe place.
• If the stairway is not protected, the travel distance
should be in line with those for single escape routes
and the final exit should be easy to see and get to
from the stairway at ground-floor level.
• High-risk rooms should not generally open directly
into a fire-protected stairway.
• Alternate means of escape usually required
Stairs & Corridors
• Minimum width 800mm stairs (increases with number of
persons) but not to exceed 1.4m unless central
handrail fitted
• 1.2m corridors
• One stairway up 4 storeys only
• Stairways to have handrails
• Treads and risers of stairs of correct dimensions
• Structure 30 mins fire resistance
Stairs, Corridors and Passages
• Fire Protection 30 minutes minimum
• Be ventilated
• Sub-divide corridors (If longer than
• Not cause bottle necks
• Height 2m
• Be continuous to the exit point
• Correct lighting
• Management actions to maintain MOE
Emergency Lighting
• Aim
– To indicate clearly the escape route
– Illuminate routes to allow safe movement
– To ensure call points and equipment can be located
• Consider natural light - day/night
• Siting
– Escape route lighting
– Open area lighting – anti-panic lighting
– High risk lighting
• Different types
– Maintained
– Sustained
– Self contained
– Low level lighting
• Testing – Daily, Monthly, 6 monthly
• The H&S (Safety Signs & Signal) Regs 96
• Two types- EC Pictorial & BS5449 Pictorial and
• Types Include – Directional arrows, equipment, alarms, assembly points
• Read from both sides
• Not obscured
Fire Doors
BS 476
Does not obstruct route when open
Self closing with smoke stops
Three hinge, Colour coded rawl plugs. i.e FD 30/30
Width 850 if more than 50 persons
Smoke sealed – intumescent strips
30 minutes fire resistance
Easily opened and in direction of travel
Magnetic hold-backs are okay
Final exit to unobstructed place of safety
Never locked
Have visibility panels
45 degree rule
Roller shutters should be capable of manual operation
Amount – 60=1 600=2 More than 600=3
1.general guidance on Vision Panel dimensions, however if Vision
Panels form part of a fire resisting door set then the area of the glass
may be determined by the fire resistance properties and the
manufactures’ s specifications etc.
2.All door glazing on traffic routes and public areas should be Safety
Glazing Standard, in addition to any fire resistance required.
Final Exit Doors
Open in direction of exit (outwardly)
Have "push bar" openers (panic bolts)
Be marked "FIRE EXIT"
Do not open directly to stairs
External area free from vegetation and
other obstacles
Place of Safety
MOE For Vulnerable People
• Evacuation lifts, refuges and chairs
• Use of graphic, aural, tactile
• Personal Emergency Evacuation
Plan (PEEP)
Fire Detection
• Smoke Detection
• Optical or ionisation
• Optical detects obscuration of light by smoke
• Ionisation detects by change in electrical charge
• Heat Detection
• Fixed rate or temperature rise
• Used where there is heat under normal conditions
• Flame Detection
• Infra-red or ultra-violet
• Usually used with other types
Ionisation Smoke Detector
• Americium 241 enables
current to flow between
the inner and outer
• As smoke enters the
detector an increase in
voltage occurs between
the two chambers.
• The voltage increase
triggers the detector at
a preset threshold.
• Ionisation detectors
respond well to fastburning fires
Optical Smoke Detector
• smoke from a fire
scatters the light from
the LED
• if smoke seen on the
two following pulses,
the alarm lights up.
• optical smoke
detectors respond
well to slow-burning
Heat Detector
• Twin thermistors detect change in heat
• Difference in temperatures triggers the alarm
• Static response detectors have one sensor at
preset temperature
• They have wide openings to allow good air
movement over the sensing thermistor
Flame Detector
• A flame detector is designed to detect ultraviolet
(UV) or infra-red (IR) radiation emitted by fire.
• Dual IR flame detectors are sensitive to lowfrequency, flickering infra-red radiation.
• Detector can operate even if the lens is
contaminated by a layer of oil, dust, water
vapour or ice.
• Flame detectors are effective in protecting areas
where flaming fires may be expected.
Alarm Systems
• Components
• Automatic detector
Spot (static)
Line (linear heat laid around an area)
Beam (of light IR large areas)
Sampling (pipe work pulling air
through a detector)
Scanning (moving/sweeping a large
• Manual call point
• Alarm sounder
• Control panel
Categories of Fire Alarms &
Detection Systems
• Systems generally designed & installed to BS 5839
• Property risk/protection (to summon the Fire & Rescue Service in
the early stages of a fire)
• Category P1 installed throughout all areas of the building.
• Category P2 Systems installed only in defined parts of a
Life Risk/ Protection
• Category M Manual system (call points & sounders only)
• Category L Automatic fire detection systems intended for the
protection of life
• L1 Installed throughout all areas of a building
• L2 Installed only in defined parts of the building
• L3 Designed to give a warning at an early enough stage to enable
occupants to escape safely before routes are impassable due to fire,
smoke or toxic gases. (other than possibly those in the room of the fires
L4 Installed in escape routes comprising of circulation areas (stairways
and corridors) Objective is to provide warning of smoke within escape
• L5 Systems in protected areas and or location of detectors designed to
satisfy a specific fire safety objective other than the above categories.
Fire Alarm Zoning
• Zones are a convenient way of dividing up a building to
assist in location of a fire.
• Zones are not physical features (normally the zone boundary
coincide with walls, floors and fire compartments)
• Zone basic rules:
• Single zone should not exceed 2,000m2
• Two faults should not remove protection from an area > 10,000m2
(for addressable systems) Addressable= Gives unique ID to the
actuating device detector/call point which has been activated.
• Floor area < 300m2 regarded as one zone.
• Total floor area > 300m2 zones restricted to single floor levels
• Exception to above: stairwells, lift shafts or other vertical shafts
should be considered as one or separate zones
• The max distance travelled within a zone to locate the fire should not
exceed 60m.
Alarm Signalling
• Objective to warm occupants of a fire situation
• One sounder located near the control panel on a
separate circuit
• Sounders should sound similar to avoid confusion
• Minimum of 65db in general areas or 5 db above
background noise.
• High noise areas visual indication may be required.
• Sleeping 75db at bedhead (30 db should be allowed per door
so sounder per bedroom is recommended)
• Impaired hearing other means of signalling may be
Alarm Receiving Centres
• Permanently manned (normally a commercial organisation)
• Upon receipt of a fire signal notify the fire service
Factors in the Selection of Fire
Alarm & Detection Systems
Life Risk
Process Risk
Behavioural issues
Social Behaviour Minimising false Alarms (unwanted
alarms, Equipment false alarms malicious alarms)
• Requirements for Vulnerable People (disabilities and/or
mobility problems)
Requirements for
Maintenance & Testing
• RRFSO 2005 States “ equipment & devices are subject to
suitable system of maintenance and maintained in an efficient
state.... Good repair”
One regime to comply with is would be:
Daily Check System is not indicating a fault if required
corrective actions are taken.
• Weekly Check Test the system by operation of a call
point (different one each week)
• Periodic Subject to RA (but should not exceed 6 months)
Check system log, visually inspect all items of
equipment(obstructed or inappropriate due to change of use),
amount of false alarms, standby power, remote signalling ,any
other checks required (beam detectors for alignment etc) all call
points over the 12 months plus cabling, programming and
audible checks.
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