Section 7 Loadbearing elements of structures

Loadbearing elements of structures

  1. Introduction
    1. Fire resistance standard
      1. Exclusions from the provisions for elements of structure
        1. Application of the fire resistance standards for loadbearing elements
          1. Additional guidance
          2. Raised storage areas
            1. Conversion to flats

              Introduction

              7.1Premature failure of the structure can be prevented by provisions for loadbearing elements of structure to have a minimum standard of fire resistance, in terms of resistance to collapse or failure of loadbearing capacity. The purpose in providing the structure with fire resistance is threefold, namely:

              • ato minimise the risk to the occupants, some of whom may have to remain in the building for some time while evacuation proceeds if the building is a large one;
              • bto reduce the risk to firefighters, who may be engaged on search or rescue operations; and
              • cto reduce the danger to people in the vicinity of the building, who might be hurt by falling debris or as a result of the impact of the collapsing structure on other buildings.

              Fire resistance standard

              7.2Elements of structure such as structural frames, beams, columns, loadbearing walls (internal and external), floor structures and gallery structures, should have at least the fire resistance given in Appendix A, Table A1.

              Exclusions from the provisions for elements of structure

              7.4The following are excluded from the definition of element of structure for the purposes of these provisions:

              • aa structure that only supports a roof, unless:
                • ithe roof performs the function of a floor, such as for parking vehicles, or as a means of escape (see Sections 2 to 4); or
                • iithe structure is essential for the stability of an external wall which needs to have fire resistance;
              • bthe lowest floor of the building;
              • ca platform floor; and
              • da loading gallery, fly gallery, stage grid, lighting bridge, or any gallery provided for similar purposes or for maintenance and repair (see definition of "Element of structure" in Appendix E).

              Application of the fire resistance standards for loadbearing elements

              7.3The measures set out in Appendix A include provisions to ensure that where one element of structure supports or gives stability to another element of structure, the supporting element has no less fire resistance than the other element (see notes to Table A2). The measures also provide for elements of structure that are common to more than one building or compartment, to be constructed to the standard of the greater of the relevant provisions. Special provisions about fire resistance of elements of structure in single storey buildings are also given and there are concessions in respect of fire resistance of elements of structure in basements where at least one side of the basement is open at ground level.

              Additional guidance

              7.5Guidance in other sections of this Approved Document may also apply if a loadbearing wall is:

              • aa compartment wall (this includes a wall common to two buildings), (see Section 8);
              • ba wall enclosing a place of special fire hazard (see Section 8, paragraph 8.12);
              • cprotecting a means of escape, (see Sections 2 to 5);
              • dan external wall, (see Sections 12 and 13); or
              • eenclosing a firefighting shaft, (see Section 17).

              7.6If a floor is also a compartment floor, see Section 8.

              Raised storage areas

              7.7Raised free-standing floors (sometimes supported by racking) are frequently erected in single storey industrial and storage buildings. Whether the structure is considered as a gallery or is of sufficient size that it is considered as a floor forming an additional storey, the normal provisions for fire resistance of elements of structure may be onerous if applied to the raised storage area.

              7.8A structure which does not have the appropriate fire resistance given in Appendix A, Table A1 is acceptable provided the following conditions are satisfied:

              • athe structure has only one tier and is used for storage purposes only;
              • bthe number of persons likely to be on the floor at any one time is low and does not include members of the public;
              • cthe floor is not more than 10m in either width or length and does not exceed one half of the floor area of the space in which it is situated;
              • dthe floor is open above and below to the room or space in which it is situated; and
              • ethe means of escape from the floor meets the relevant provisions in Sections 3, 4 and 5.

              Notes:Where the lower level is provided with an automatic detection and alarm system meeting the relevant recommendations of BS 5839-1:2002, then the floor size may be increased to not more than 20m in either width or length.
              The maximum dimensions provided above have been set in order to limit the distance that a firefighter may need to travel over or under floor to effect a rescue. Where agreed locally it may be possible to vary these dimensions, however, the safety of firefighters who may be on or underneath these floors must be taken into account.
              Where the building is fitted throughout with an automatic sprinkler system in accordance with paragraph 0.16, there are no limits on the size of the floor.

              Conversion to flats

              7.9Where an existing house or other building is converted into flats, there is a material change of use to which Part B of the regulations applies. Where the existing building has timber floors and these are to be retained, the relevant provisions for fire resistance may be difficult to meet.

              7.10Provided that the means of escape conform to Section 3 and are adequately protected, a 30 minute standard of fire resistance could be accepted for the elements of structure in a building having not more than three storeys.

              Where the altered building has four or more storeys the full standard of fire resistance given in Appendix A would normally be necessary.

              • 1 Gallery floors with no alternative exit Diagram 1 Gallery floors with no alternative exit
              • 2 Flat where all habitable rooms have direct access to an entrance hall Diagram 2 Flat where all habitable rooms have direct access to an entrance hall
              • 3 Flat with restricted travel distance from furthest point to entrance Diagram 3 Flat with restricted travel distance from furthest point to entrance
              • 4 Flat with an alternative exit but where all habitable rooms have no direct acess to an entrance hall Diagram 4 Flat with an alternative exit but where all habitable rooms have no direct access to an entrance hall
              • 5 Multi-storey flat with alternative exits from each habitable room except at entrance level 5 Multi-storey flat with alternative exits from each habitable room except at entrance level
              • 6 Multi-storey flat with protected entrance hall and landing Diagram 6 Multi-storey flat with protected entrance hall and landing
              • 7 Flats served by one common stair,png Diagram 7 Flats served by one common stair
              • 8 Flats served by more than one common stair 8 Flats served by more than one common stair
              • 9 Common escape route in small single stair building Diagram 9 Common escape route in small single stair building
              • 10 Travel distance in dead-end condition 10 Travel distance in dead-end condition
              • 11 Alternative escape routes 11 Alternative escape routes
              • 12 Inner room and access room 12 Inner room and access room
              • 13 Exits in a central core Diagram 13 Exits in a central core
              • 14 Open Connections Diagram 14 Open Connections
              • 15 Merging flows at final exit Diagram 15 Merging flows at final exit
              • 16 Subdivision of corridors Diagram 16 Subdivision of corridors
              • 17 Dead-end corridors Diagram 17 Dead-end corridors
              • 18 Maximum travel distances in a small two or three storey premises with a single protected stair to each storey Diagram 18 Maximum travel distances in a small two or three storey premises with a single protected stair to each storey
              • 19 Progressive horizontal evacuation in care homes Diagram 19 Progressive horizontal evacuation in care homes
              • 20 Refuge formed by compartmentation Diagram 20 Refuge formed by compartmentation
              • 21 Refuge formed in a protected stairway Diagram 21 Refuge formed in a protected stairway
              • 22 Max travel distance in a small three storey premises with a single stair to each storey Diagram 22 Max travel distance in a small three storey premises with a single stair to each storey
              • 23 Max travel distance in a small two storey premises with a single open stair Diagram 23 Max travel distance in a small two storey premises with a single open stair
              • 24 External protection to protected stairways Diagram 24 External protection to protected stairways
              • 25 Fire resistance of areas adjacent to external stairs 25 Fire resistance of areas adjacent to external stairs
              • 26 Lighting diffuser in relation to ceiling Diagram 26 Lighting diffuser in relation to ceiling
              • 27 Layout restrictions on Class 3 plastic roofflights TP-b rooflights and TP b lighting diffusers Diagram 27 Layout restrictions on Class 3 plastic rooflights TP-b rooflights and TP b lighting diffusers
              • 27a Layout restrictions on small Class 3 plastic rooflights TP b rooflights and lighting diffusers Diagram 27a Layout restrictions on small Class 3 plastic rooflights TP b rooflights and lighting diffusers
              • 28 Compartment floors illustration of guidance in paragraph 8.16 Diagram 28 Compartment floors illustration of guidance in paragraph 8.16
              • 29 Compartment walls and compartment floors with reference to relevant paragraphs in Section 8 Diagram 29 Compartment walls and compartment floors with reference to relevant paragraphs in Section 8
              • 30 Junction of compartment wall with roof Diagram 30 Junction of compartment wall with roof
              • 31 Protected shafts Diagram 31 Protected shafts
              • 32 Uninsulated glazed screen separating protected shaft from lobby or corridor Diagram 32 Uninsulated glazed screen separating protected shaft from lobby or corridor
              • 33 Provisions for cavity barriers Diagram 33 Provisions for cavity barriers
              • 34 Cavity wall excluded from provisions for cavity barriers Diagram 34 Cavity wall excluded from provisions for cavity barriers
              • 35 Fire-resisting ceiling below concealed space Diagram 35 Fire-resisting ceiling below concealed space
              • 36 Provisions for cavity barriers in double-skinned insulated roof sheeting Diagram 36 Provisions for cavity barriers in double-skinned insulated roof sheeting
              • 37 Pipes penetrating structure Diagram 37 Pipes penetrating structure
              • 38 Enclosure for drainage or water supply pipes Diagram 38 Enclosure for drainage or water supply pipes
              • 39 Flues penetrating compartment walls or floors Diagram 39 Flues penetrating compartment walls or floors
              • 40 Provisions for external surfaces or walls Diagram 40 Provisions for external surfaces or walls
              • 41 Relevant boundary Diagram 41 Relevant boundary
              • 42 Notional boundary Diagram 42 Notional boundary
              • 43 Status of combustible surface material as unprotected area Diagram 43 Status of combustible surface material as unprotected area
              • 44 Unprotected areas which may be disregarded in assessing the separation distance from the boundary Diagram 44 Unprotected areas which may be disregarded in assessing the separation distance from the boundary
              • 45 The effect of a canopy on separation distance Diagram 45 The effect of a canopy on separation distance
              • 46 Permitted unprotected areas in small residential buildings Diagram 46 Permitted unprotected areas in small residential buildings
              • 47 Limitations on spacing and size of plastic rooflights having a Class 3 or Class D-s3 d2 or TP b lower surface Diagram 47 Limitations on spacing and size of plastic rooflights having a Class 3 or Class D-s3 d2 or TP b lower surface
              • 48 Example of building footprint and perimeter Diagram 48 Example of building footprint and perimeter
              • 49 Relationship between buildings and hardstanding access roads for high reach fire appliances Diagram 49 Relationship between buildings and hardstanding access roads for high reach fire appliances
              • 50 Turning facilities Diagram 50 Turning facilities
              • 51 Provision of firefighting shafts Diagram 51 Provision of firefighting shafts
              • 52 Components of a firefighting shaft Diagram 52 Components of a firefighting shaft
              • 53 Fire-resisting construction for smoke outlet shafts Diagram 53 Fire-resisting construction for smoke outlet shafts
              • C1 Measurement of door width Diagram C1 Measurement of door width
              • C2 Cubic capacity Diagram C2 Cubic capacity
              • C3 Area Diagram C3 Area
              • C4 Height of building Diagram C4 Height of building
              • C5 Number of storeys Diagram C5 Number of storeys
              • C6 Height of top storey in buildingC6 Height of top storey in building Diagram C6 Height of top storey in building
              • C7 Free area of smoke ventilators Diagram C7 Free area of smoke ventilators
              • D1 Classification of Purpose Groups Diagram D1 Classification of Purpose Groups
              • E1 Recessed car parking areas Diagram E1 Recessed car parking areas
              • Table 1 Limitations on distance of travel in common areas of blocks of flats - see par 2.23 Table 1 Limitations on distance of travel in common areas of blocks of flats - see par 2.23
              • Table 2 Limitations on travel distance Table 2 Limitations on travel distance
              • Table 3 Minimum number of escape routes and exits from a room tier or storey Table 3 Minimum number of escape routes and exits from a room tier or storey
              • Table 4 Widths of escape routes and exits Table 4 Widths of escape routes and exits
              • Table 5 Maximum distances of travel in small premises with a protected stair Table 5 Maximum distances of travel in small premises with a protected stair
              • Table 6 Minimum widths of escape stairs Table 6 Minimum widths of escape stairs
              • Table 7 Capacity of a stair for basements and for simultaneous evacuation of the building Table 7 Capacity of a stair for basements and for simultaneous evacuation of the building
              • Table 8 Minimum width of stairs designed for phased evacuation Table 8 Minimum width of stairs designed for phased evacuation
              • Table 9 Provisions for escape lighting Table 9 Provisions for escape lighting
              • Table 10 Classification of linings Table 10 Classification of linings
              • Table 11 Limitations applied to thermoplastic rooflights and lighting diffusers in suspended ceilings and Class 3 plastic rooflights Table 11 Limitations applied to thermoplastic rooflights and lighting diffusers in suspended ceilings and Class 3 plastic rooflights
              • Table 12 Maximum dimensions of building or compartment - non-residential buildings Table 12 Maximum dimensions of building or compartment - non-residential buildings
              • Table 13 Maximum dimensions of cavities in non-domestic buildings - purpose Groups 2-7 Table 13 Maximum dimensions of cavities in non-domestic buildings - purpose Groups 2-7
              • Table 14 Maximum nominal internal diameter of pipes passing through a compartment wall-floor - see par 10.5 onwards Table 14 Maximum nominal internal diameter of pipes passing through a compartment wall-floor - see par 10.5 onwards
              • Table 15 Permitted unprotected areas in small buildings or compartments Table 15 Permitted unprotected areas in small buildings or compartments
              • Table 16 Limitations on roof coverings Table 16 Limitations on roof coverings
              • Table 17 Class 3 or Class D-s3 d2 plastic rooflights limitations on use and boundary distance Table 17 Class 3 or Class D-s3 d2 plastic rooflights limitations on use and boundary distance
              • Table 18 TP a and TP b plastic rooflights limitations on use and boundary distance Table 18 TP a and TP b plastic rooflights limitations on use and boundary distance
              • Table 19 Fire and rescue service vehicle access to buildings excluding blocks of flats not fitted with fire mains Table 19 Fire and rescue service vehicle access to buildings excluding blocks of flats not fitted with fire mains
              • Table 20 Typical fire and rescue service vehicle access route specification Table 20 Typical fire and rescue service vehicle access route specification
              • Table A1 Specific provisions of test for fire resistance of elements of structure etc Table A1 Specific provisions of test for fire resistance of elements of structure etc
              • Table A1 continued Table A1 continued
              • Table A2 Minimum periods of fire resistance Table A2 Minimum periods of fire resistance
              • Table A3 Limitations on fire-protecting suspended ceilings - see Table A1 Note 4 Table A3 Limitations on fire-protecting suspended ceilings (see Table A1 Note 4)
              • Table A4 Limitations on the use of uninsulated glazed elements on escape routes Table A4 Limitations on the use of uninsulated glazed elements on escape routes]
              • Table A5 Notional designations of roof coverings Table A5 Notional designations of roof coverings
              • Table A6 Use and definitions of non-combustible materials Table A6 Use and definitions of non-combustible materials
              • Table A7 Use and definitions of materials of limited combustibility Table A7 Use and definitions of materials of limited combustibility
              • Table A8 Typical performance rating of some generic materials and products Table A8 Typical performance rating of some generic materials and products
              • Table B1 Provisions for fire doors Table B1 Provisions for fire doors
              • Table C1 Floor space factors Table C1 Floor space factors
              • Table D1 Classification of Purpose Groups Table D1 Classification of Purpose Groups
              • Table Maximum dimensions of building or compartment - non-residential buildings Table Maximum dimensions of building or compartment (non-residential buildings)