Annex 2.D Resistance to fire
This annex provides guidance on how to establish the resistance to fire of a building element or component. Whilst it could be argued that occupants of a building only need minutes to reach relative safety such as a protected zone, it should be remembered that the fire tests used to establish fire resistance duration in terms of time, do not replicate a real fire. In order to ensure the safe evacuation of the building occupants and to ensure that fire-fighters are not placed at undue risk, it is necessary to apply certain factors of safety to the fire resistance duration for structural and non-structural fire protection. For example, in a large intense fire, a British or European Standard 30 minute fire door may not last for more than the few minutes necessary to evacuate the building.
Transition period - fire resistance durations are established from the guidance to Standards 2.1 to 2.15. Reference throughout this document to a short, medium or long fire resistance duration, will be satisfied by following the guidance in the table to this annex titled ‘Fire resistance duration for common building elements or components’. The designer is free to choose materials or products which satisfy either the British Standard Tests or the Harmonised European Tests.
Any test evidence or assessment used to substantiate the fire resistance rating of a wall, floor, ceiling, door or shutter should be carefully checked to ensure that it demonstrates compliance with appropriate fire tests and performance criteria contained in this handbook and is applicable to the complete installed assembly. For example, in the case of floors or ceilings small differences in details such as openings for lighting or ventilation can significantly affect the rating. Similarly, fire doors may also have small differences in detail such as glazing apertures, intumescent strips, door frames and ironmongery etc which may significantly affect the rating.
British and European fire tests will co-exist in use until the British Standard classifications are withdrawn.
In the case of a single storey steel portal frame building constructed in accordance with the guidance in clause 2.3.1, the columns of the portal frame should be designed with fixed column base connections. Alternatively, the portal frame may be designed in accordance with the publication 'Single storey steel framed buildings in fire boundary conditions' published in October 2002 by The Steel Construction Institute (SCI-P313).
A steel portal frame member supporting or forming part of a separating wall or compartment wall, the enclosing structure of a protected zone or an external wall requiring a fire resistance duration (as in the guidance to Standard 2.6), should also be fire resisting. The fire resistance duration should only be applied to that part of the member built into or directly supporting the wall up to the underside of the haunch or the underside of there after where there is no haunch, and shall not apply to any other part not withstanding that it is part of the same portal frame.
Where a gable steel portal frame member attracts a fire resistance duration because of its proximity to the boundary (see guidance to Standard 2.6), the entire portal frame should have the same fire resistance duration.
Where the topmost storey of a steel framed open sided car park is at a height of not more than 18m above ground, the following alternative guidance to Standard 2.1 could be used for the structural frame, columns and beams:
beams supporting concrete floors, each beam having a maximum Hp/A = 230m - ¹, and
free standing columns, each having a maximum Hp/A = 180m - ¹, and
wind bracing and struts, each having a maximum Hp/A = 210m - ¹.
Where Hp = heated perimeter of the section in m, and
A = gross cross-sectional area of the section in m2.
Table 2.19. fire resistance duration for common building elements of components
| Construction | Fire resistance duration | British Standards Load bearing capacity (mins) | British Standards Integrity (mins) | British Standards Insulation (mins) | European Standards | Test exposure |
|---|---|---|---|---|---|---|
| 1. Structural frame, column or beam | Short | 30 | None | None | R 30 | Faces exposed on the inside |
| Medium | 60 | None | None | R 60 | ||
| Long | 120 | None | None | R 120 | ||
| 2. Compartment floor, separating floor or a floor, flat roof or access deck protecting routes of escape (see clause 2.0.6) | Short | 30 | 30 | 30 | REI 30 | From the underside |
| Medium | 60 | 60 | 60 | REI 60 | ||
| Long | 120 | 120 | 120 | REI 120 | ||
| 3. Floor, other than a floor in 2 | Short | 30 | None | None | R 30 | From the underside |
| Medium | 60 | None | None | R 60 | ||
| Long | 120 | None | None | R 120 | ||
| 4. Fire shutter in a compartment floor (see clause 2.1.14) | Short | None | 30 | None | E 30 | From the underside when fitted in frame |
| Medium | None | 60 | None | E 60 | ||
| Long | None | 120 | None | E 120 | ||
| 5. Compartment wall, sub-compartment wall, separating wall, or an internal wall or screen used as a protected route of escape (see clause 2.0.6) | Short | 30 [4] | 30 | 30 [5] | REI 30 [4,5] | Each side separately |
| Medium | 60 [4] | 60 | 60 | REI 60 [4] | ||
| Long | 120 [4] | 120 | 120 | REI 120 [4] | ||
| 6. Load-bearing wall, other than a wall in 5 | Short | 30 | None | None | R 30 | Each side separately |
| Medium | 60 | None | None | R 60 | ||
| Long | 120 | None | None | R 120 | ||
| 7. Fire door in a wall in 5 | Short | None | 30 [6] | None | E 30 Sa [6] | Each side separately, when fitted in frame |
| Medium | None | 60 [6] | None | E 60 Sa [6] | ||
| Long | None | 120 [6, 7] | None | E 120 Sa [6, 7] | ||
| 8. Fire shutter in a compartment wall (see clause 2.1.14) or in a wall or screen protecting routes of escape (see clause 2.0.6) | Short | None | 30 | 30 [8] | EI 30 [8] | Each side separately, when fitted in frame [8] |
| Medium | None | 60 | 60 [8] | EI 60 [8] | ||
| Long | None | 120 | 120 [8] | EI 120 [8] | ||
| 9. External wall more than 1 m from a boundary [1, 2] | Short | 30 [4] | 30 | None | RE 30 [4] | From the inside only |
| Medium | 60 [4] | 60 | 30 | RE 60 & I 30 [4] | ||
| 10. External wall not more than 1 m from a boundary [1, 2] | Short | 30 [4] | 30 | 30 | REI 30 [4] | From the inside only |
| Medium | 60 [4] | 60 | 60 | REI 60 [4] | ||
| 11. Horizontal cavity barrier [3] | Short | None | 30 | None | E 30 | From the underside |
| 12. Vertical cavity barrier [3] | Short | None | 30 | None | E 30 | Each side separately |
| 13. Ceiling dispensing with a cavity barrier (see clauses 2.4.2b, 2.4.2c, 2.4.3 and 2.4.4) | Short | None | 30 | 30 | EI 30 | From the underside |
| 14. Roof against an external wall (see annex 2.A.1) | Medium | None | 60 | 60 | EI 60 | From the inside |
Additional information:
An external wall includes an external wall used to protect routes of escape (see clause 2.0.6) but excludes an unprotected area calculated in accordance with clauses 2.6.1 to 2.6.4.
Any shutter or door in an external wall, which is not included in the calculation of unprotected area, should have the same fire resistance duration and test exposure as the external wall.
In a timber or metal stud wall or partition the following will also be deemed to have a short fire resistance duration:
polythene sleeved mineral wool, or mineral wool slab, in either case under compression when installed, or
calcium silicate, cement based or gypsum based board at least 12mm thick, or
steel at least 0.5mm thick, or
timber at least 38mm thick.
If the construction is non load-bearing, none in the case of column 3 and no load-bearing (R) in the case of column 6.
None in the case of column 5 and E30 in the case of column 6 for a single openable window not more than 1m2 in a room in a protected zone as described in clause 2.9.24.
Unless the fire door is in an external wall or a lift door or pressurisation techniques following the guidance in BS EN 12101 Part 6: 2005 are used, the fire door should also either:
in the case of column 4, have smoke seals fitted unless the leakage rate does not exceed 3m³/m/hour, head and jambs only, when tested at 25Pa according to BS 476: Part 31: 1983 (section 31.1) with AMD 8366/ November 1994, or
in the case of column 6, attain the additional classification of Sa when tested to BS EN 1634-3.
Medium fire resistance duration is sufficient for a fire door in the enclosing structure of a fire-fighting shaft (see clause 2.1.9).
None in the case of column 5, and no insulation (I) in the case of column 6, where:
the width of the fire shutter or the aggregate width of any fire shutters in the wall or part of the wall is not more than one-quarter of the length of the relevant part of the wall, or
people or vehicle circulation routes are clearly marked and will prevent any fire load adjacent to the shutter (e.g. at stairs, escalators, lifts and corridors).
The recommended fire resistance duration can be attained where the construction follows the guidance in the columns 3, 4 and 5 of table 2.19. The tests and specifications are:
Clause 10 of BS 476: Part 20: 1987, when read in conjunction with; for load-bearing elements, BS 476: Part 21: 1987, for non-load-bearing elements, BS 476: Part 22: 1987, for components, BS 476: Part 23: 1987, for ventilation ducts, BS 476: Part 24: 1987, for fire door assemblies with non-metallic leaves, BS 8214: 1990, Sections 1 and 2
for structural steelwork, BS 5950: Part 8: 2003 or ‘Fire Safe Design: A new approach to multi-storey steel framed buildings’ published by The Steel Construction Institute (within the limitations described in the SCI Publication P288)
for the structural use of timber, BS 5268: Part 4: Sections 4.1 and 4.2: 1990
for the structural use of concrete, BS 8110: Part 2: 1985, Section 4.3 ‘Tabulated data (method 1)’
an appropriate specification given in the Building Research Establishment Report BR 128 ‘Guidelines for the Construction of Fire Resisting Structural Elements’ (BRE 1988).
The recommended fire resistance duration can be attained where the construction follows the guidance in column 6 of table 2.19 as specified in Commission Decision 2000/367/EC of 3/5/2000 implementing Council Directive 89/106/EEC as regards the classification of the resistance to fire of construction products, construction works and parts thereof.
BS EN 13501-2: 2007, Fire classification of construction products and building elements, Part 2 - Classification using data from fire resistance tests (excluding products for use in ventilation systems).
BS EN 13501-3: 2005, Fire classification of construction products and building elements. Classification using data from fire resistance tests on products and elements used in building service installations: fire resisting ducts and fire dampers (other than smoke control systems).
BS EN 13501- 4: 2007, Fire classification of construction products and building elements, Part 4 - Classification using data from fire resistance tests on smoke control systems.
The tests and specifications are:
BS EN 1363-1: 1999, Fire resistance tests, Part 1 - General requirements.
BS EN 1363-2: 1999, Fire resistance tests, Part 2 - Alternative and additional procedures.
BS EN 1363-3: 2000, Fire resistance tests, Part 3 - Verification of furnace performance.
BS EN 1364-1: 1999, Fire resistance tests for non load-bearing elements - Part 1: Walls.
BS EN 1364-2: 1999, Fire resistance tests for non load-bearing elements - Part 2: Ceilings.
BS EN 1365-1: 1999, Fire resistance tests for load-bearing elements - Part 1: Walls.
BS EN 1365-2: 2000, Fire resistance tests for load-bearing elements - Part 2: Floors and roofs.
BS EN 1365-3: 2000, Fire resistance tests for load-bearing elements - Part 3: Beams.
BS EN 1365-4: 1999, Fire resistance tests for load-bearing elements - Part 4: Columns.
BS EN 1366-1: 1999, Fire resistance tests for service installations - Part 1: Ducts.
BS EN 1366-2: 1999, Fire resistance tests for service installations - Part 2: Fire dampers.
BS EN 1634-1: 2008, Fire resistance and smoke control tests for door and shutter assemblies, openable windows and elements of building hardware, Part 1 – Fire resistance tests for doors, shutters and openable windows.
BS EN 1634-2: 2008, Fire resistance and smoke control tests for door and shutter assemblies, openable windows and elements of building hardware, Part 2 – Fire resistance characterisation test for elements of building hardware.
BS EN 1634-3: 2004, Fire resistance and smoke control tests for door and shutter assemblies, openable windows and elements of building hardware, Part 3 – Smoke control test for door and shutter assemblies.
BS EN 81-58: 2003, Safety rules for the construction and installation of lifts – Examination and tests - Part 58: landing doors fire resistance test may be used in accordance with Council Directive 95/16/EC of 29/6/1995 implementing the Lifts Regulations 1997 (SI 1997/831).
Any reference to European Standards for Structure (Structural Eurocodes) must be taken to include the relevant UK National Annex:
BS EN 1991-1-2:2002, Eurocode 1: Actions on structures – Part 1-2: General actions – Actions on structures exposed to fire.
BS EN 1992-1-2:2004, Eurocode 2: Design of concrete structures – Part 1-2: General rules – Structural fire design.
BS EN 1993-1-2:2005, Eurocode 3: Design of steel structures – Part 1-2: General rules – Structural fire design.
BS EN 1994-1-2:2005, Eurocode 4: Design of composite steel and concrete structures – Part 1-2: General rules – Structural fire design.
BS EN 1995-1-2:2004: Eurocode 5: Design of timber structures – Part 1-2: General rules – Structural fire design.
BS EN 1996-1-2:2005: Eurocode 6: Design of masonry structures – Part 1-2: General rules – Structural fire design.
BS EN 1999-1-2:2007: Eurocode 9: Design of aluminium structures – Part 1-2: General rules – Structural fire design.