Items where Subject is "Section 11: Resisting fire spread from one building to another"
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- Section 11: Resisting fire spread from one building to another (62)
Book Section
The following assumptions enable a reasonable standard of resistance to the spread of fire to be specified.
a. The size of a fire depends on the compartmentation within the building. A fire may involve a complete compartment, but will not spread to other compartments.
b. The intensity of a fire is related to the building use, but can be moderated by a sprinkler system.
c. Fires in ‘residential’ and ‘assembly and recreation’ buildings (purpose groups 1, 2 and 5) represent a greater risk to life.
d. A building on the far side of the relevant boundary meets both of the following conditions.
i. Has a similar elevation to the one in question.
ii. Is the same distance as the one in question from the common boundary.
e. The radiated heat passing through any part of the fire resisting external wall may be discounted.
Exclude external walls of stairways in a protected shaft when assessing unprotected areas (see Diagram 11.5).
In an otherwise protected wall, small unprotected areas may be ignored where they meet the conditions in Diagram 11.5.
Where both of the following apply, separation distances may be determined from the wall rather than from the edge of the canopy (Diagram 11.6).
a. The canopy is attached to the side of a building.
b. The edges of the canopy are a minimum of 2m from the relevant boundary.
Canopies that fall within class 6 or class 7 of Schedule 2 to the regulations (Exempt Buildings and Work) are exempt from the Building Regulations.
Space separation may be disregarded if a canopy is all of the following.
a. Free-standing.
b. Above a limited risk or controlled hazard.
c. A minimum of 1000mm from the relevant boundary.
Two simple methods are given for calculating the acceptable amount of unprotected area in an external wall that is a minimum of 1000mm from any point on the relevant boundary. More precise methods are described in BRE report BR 187 and may be used instead. When using BR 187 the following radiation intensity at each unprotected area should be assumed.
a. 84kw/m2 if the purpose group of the building is ‘residential’ (purpose groups 1 or 2), ‘office’ (purpose group 3) or ‘assembly and recreation’ (purpose group 5) or if the building is an open-sided multi-storey car park (purpose group 7(b)).
b. 168kw/m2 if the purpose group of the building is ‘shop and commercial’ (purpose group 4), ‘industrial’ (purpose group 6) or ‘storage and other non-residential’ (purpose group 7(a)).
This method applies to small buildings intended to be used for blocks of flats or dwellinghouses.
The building should not exceed three storeys in height (excluding basements) or 24m in length. Each side of the building should meet the limits stated in Diagram 11.7. Any small unprotected areas falling within the limits shown in Diagram 11.5 can be ignored.
This method may be used for buildings or compartments for which method 1 is not appropriate.
Where regulation 7(2) applies, that regulation prevails over the provisions within this section.
The building should not exceed 10m in height. Each side of the building should meet the limits stated in Table 11.1. Any areas falling within the limits shown in Diagram 11.5 can be ignored.
If a building is fitted throughout with a sprinkler system in accordance with Appendix E, either of the following is permitted.
a. The boundary distance can be halved, to a minimum distance of 1m.
b. The amount of unprotected area can be doubled.
If a reduced separation distance between buildings, or increased amount of unprotected area, is required, smaller compartments should be considered.
The fire resistance of a wall depends on its distance from the relevant boundary (see Diagram 11.1). Separation distances are measured to boundaries to ensure that the location and design of buildings on adjoining sites have no influence on the building under consideration.
The boundary that a wall faces is the relevant boundary (Diagram 11.2). It may be one of the following.
a. The site boundary.
b. The centre line of a space where further development is unlikely, such as a road, railway, canal or river.
c. An assumed notional boundary between two buildings on the same site (Diagram 11.3) where either of the following conditions is met.
i. One or both of the buildings are in the "residential" or "assembly and recreation" purpose groups (purpose group 1, 2 or 5).
ii. The buildings will be operated/managed by different organisations.
Parts of an external wall with less fire resistance than the appropriate amount given in Appendix B, Table B4, are called unprotected areas.
Where a fire resisting external wall has an external surface material that is worse than class B-s3, d2 and is more than 1mm thick, that part of the wall should be classified as an unprotected area equating to half its area (Diagram 11.4).
Unprotected areas should meet the conditions in Diagram 11.5, and the rest of the wall should be fire resisting from both sides.
External surface materials facing the boundary should be class B-s3, d2 or better.
Unprotected areas should not exceed the result given by one of the methods in paragraph 11.16, and the rest of the wall (if any) should be fire resisting but only from the inside of the building.
Table 12.3 sets the limitations for using thermoplastic materials with a TP(a) rigid or TP(b) (see also Diagram 12.1) classification. The method of classifying thermoplastic materials is given in Appendix B.
When used in rooflights, unwired glass a minimum of 4mm thick can be regarded as having a BROOF(t4) classification.
Guidance on the design and construction of fire mains is given in BS 9990.
For building work involving the erection or extension of a relevant building (i.e. a building to which the Regulatory Reform (Fire Safety) Order 2005 applies, or will apply), or the relevant change of use of a building, fire safety information should be given to the responsible person at one of the following times.
a. When the project is complete.
For building work involving the erection or extension of a relevant building (i.e. a building to which the Regulatory Reform (Fire Safety) Order 2005 applies, or will apply), or the relevant change of use of a building, fire safety information should be given to the responsible person at one of the following times.
b. When the building or extension is first occupied.
Basic information on the location of fire protection measures may be sufficient. An as-built plan of the building should be provided showing all of the following.
a. Escape routes – this should include exit capacity (i.e. the maximum allowable number of people for each storey and for the building).
Basic information on the location of fire protection measures may be sufficient. An as-built plan of the building should be provided showing all of the following.
b. Location of fire-separating elements (including cavity barriers in walk-in spaces).
Basic information on the location of fire protection measures may be sufficient. An as-built plan of the building should be provided showing all of the following.
c. Fire doorsets, fire doorsets fitted with a self-closing device and other doors equipped with relevant hardware.
Basic information on the location of fire protection measures may be sufficient. An as-built plan of the building should be provided showing all of the following.
d. Locations of fire and/or smoke detector heads, alarm call points, detection/alarm control boxes, alarm sounders, fire safety signage, emergency lighting, fire extinguishers, dry or wet fire mains and other firefighting equipment, and hydrants outside the building.
Basic information on the location of fire protection measures may be sufficient. An as-built plan of the building should be provided showing all of the following.
e. Any sprinkler systems, including isolating valves and control equipment.
Basic information on the location of fire protection measures may be sufficient. An as-built plan of the building should be provided showing all of the following.
f. Any smoke control systems, or ventilation systems with a smoke control function, including mode of operation and control systems.
Basic information on the location of fire protection measures may be sufficient. An as-built plan of the building should be provided showing all of the following.
g. Any high risk areas (e.g. heating machinery).
Details should be provided of all of the following.
a. Specifications of fire safety equipment provided, including routine maintenance schedules.
Details should be provided of all of the following.
b. Any assumptions regarding the management of the building in the design of the fire safety arrangements.
Details should be provided of all of the following.
c. Any provision enabling the evacuation of disabled people, which can be used when designing personal emergency evacuation plans.
A detailed record should be provided of both of the following.
a. The fire safety strategy.
A detailed record should be provided of both of the following.
b. Procedures for operating and maintaining any fire protection measures. This should include an outline cause and effect matrix/strategy for the building.
Further guidance is available in clause 9 and Annex H of BS 9999.
The records should include details of all of the following.
a. The fire safety strategy, including all assumptions in the design of the fire safety systems (such as fire load). Any risk assessments or risk analysis.
The records should include details of all of the following.
b. All assumptions in the design of the fire safety arrangements for the management of the building.
The records should include details of all of the following.
c. All of the following.
i. Escape routes (including occupant load and capacity of escape routes).
ii. Any provision to enable the evacuation of disabled people.
iii. Escape strategy (e.g. simultaneous or phased).
iv. Muster points.
The records should include details of all of the following.
d. All passive fire safety measures, including all of the following.
i. Compartmentation (i.e. location of fire-separating elements).
ii. Cavity barriers.
iii. Fire doorsets, including fire doorsets fitted with a self-closing device and other doors equipped with relevant hardware (e.g. electronic security locks).
iv. Duct dampers.
v. Fire shutters.
The records should include details of all of the following.
d. All passive fire safety measures, including all of the following.
i. Compartmentation (i.e. location of fire-separating elements).
The records should include details of all of the following.
d. All passive fire safety measures, including all of the following.
ii. Cavity barriers.
The records should include details of all of the following.
d. All passive fire safety measures, including all of the following.
iii. Fire doorsets, including fire doorsets fitted with a self-closing device and other doors equipped with relevant hardware (e.g. electronic security locks).
The records should include details of all of the following.
d. All passive fire safety measures, including all of the following.
iv. Duct dampers.
The records should include details of all of the following.
d. All passive fire safety measures, including all of the following.
iv. Duct dampers.
The records should include details of all of the following.
d. All passive fire safety measures, including all of the following.
v. Fire shutters.
The records should include details of all of the following.
e. All of the following.
i. Fire detector heads.
ii. Smoke detector heads.
iii. Alarm call points.
iv. Detection/alarm control boxes.
v. Alarm sounders.
vi. Emergency communications systems.
vii. CCTV.
viii. Fire safety signage.
ix. Emergency lighting.
x. Fire extinguishers.
xi. Dry or wet fire mains and other firefighting equipment.
xii. Other interior facilities for the fire and rescue service.
xiii. Emergency control rooms.
xiv. Location of hydrants outside the building.
xv. Other exterior facilities for the fire and rescue service.
The records should include details of all of the following.
f. All active fire safety measures, including both of the following.
i. Sprinkler system(s) design, including isolating valves and control equipment.
ii. Smoke control system(s) (or heating, ventilation and air conditioning system with a smoke control function) design, including mode of operation and control systems.
The records should include details of all of the following.
g. Any high risk areas (e.g. heating machinery) and particular hazards.
The records should include details of all of the following.
h. Plans of the building as built, showing the locations of the above.
The records should include details of all of the following.
i. Both of the following.
i. Specifications of any fire safety equipment provided, including all of the following.
• Operational details.
• Operators’ manuals.
• Software.
• System zoning.
• Routine inspection, testing and maintenance schedules.
ii. Records of any acceptance or commissioning tests.
The records should include details of all of the following.
i. Both of the following.
i. Specifications of any fire safety equipment provided, including all of the following.
• Operational details.
• Operators’ manuals.
• Software.
• System zoning.
• Routine inspection, testing and maintenance schedules.
The records should include details of all of the following.
i. Both of the following.
ii. Records of any acceptance or commissioning tests.
The records should include details of all of the following.
j. Any other details appropriate for the specific building.
Image
Wall sufficiently distant from relevant boundary to be a 100% unprotected area
Wall on or very close to the relevant boundary: very limited amounts of unprotected area
Wall not on, or not very close to, but not sufficiently far from relevant boundary that it can be a wholly unprotected area
Amount of unprotected area dependent on distance from relevant boundary
See para 11.4
NOTES:
Intermediate values may be obtained by interpolation.
1.The total percentage of unprotected area is found by dividing the total unprotected area by the area of a rectangle that encloses all the unprotected areas, and multiplying the result by 100.
This boundary coincides with and is therefore relevant to side A
The boundary is parallel to side B2
But the relevant boundary may be the centre line of a road, railway, canal or river
NOTES:
This boundary is at less than 80 degrees to side C and is therefore relevant to side C
This diagram sets out the rules that apply in respect of a boundary for it to be considered as a relevant boundary.
For a boundary to be relevant it should comply with one of the following:
a. Coincide with the side of the building (A).
b. Be parallel to the side of the building (B1 or B2).
c. Be at an angle of maximum 80 degrees to the side of the building (C).
This boundary is parallel to and therefore relevant to side B1
See para 11.5
NOTES:
The notional boundary should be set in the area between the two buildings using the following rules:
1. The notional boundary is assumed to exist in the space between the buildings and is positioned so that one of the buildings would comply with the provisions for space separation having regard to the amount of its unprotected area. In practice, if one of the buildings is existing, the position of the boundary will be set by the space separation factors for that building.
2. The siting of the new building, or the second building if both are new, can then be checked to see that it also complies, using the notional boundary as the relevant boundary for the second building.
Notional boundary
Site boundary
Compliance with the provisions for space separation in respect of building A
Compliance with the provisions for space separation in respect of building B
See para 11.5
Area of fire resisting wall with materials more than 1mm thick and with a reaction to fire performance worse than class B-s3, d2 = a x b
Area of wall counted as unprotected area = 0.5a x b
Area of fire resisting wall with materials having a reaction to fire performance better than class B-s3, d2
See para 11.7
The unprotected area of the external wall of a stairway forming a protected shaft may be disregarded for separation distance purposes
Roofs pitched at an angle of less than 70 degrees may be disregarded for separation distance purposes
Represents an unprotected area of not more than 1m2 which may consist of two or more smaller areas within an area of 1000mm X 1000mm
Represents an area of not more than 0.1m2
See para 11.11
NOTE: Projections from the building line, such as a canopy or a loading platform, can be ignored when assessing separation distance. This does not apply where the canopy is enclosed by side walls.
Distance to relevant boundary measured from building line
See para 11.12
Minimum distance (a) between side of building and relevant boundary (m) Maximum total area of unprotected areas (m2)
See para 11.18