Section 3 Design for horizontal escape – buildings other than flats

Design for horizontal escape – buildings other than flats

  1. Introduction
    1. Escape route design
      1. Number of escape routes and exits
        1. Single escape routes and exits
          1. Access control measures
            1. Number of occupants and exits
              1. Alternative escape routes
                1. Inner rooms
                  1. Planning of exits in a central core
                    1. Open spatial planning
                      1. Access to storey exits
                        1. Separation of circulation routes from stairways
                          1. Storeys divided into different uses
                            1. Storeys divided into different occupancies
                              1. Height of escape routes
                                1. Width of escape routes and exits
                                  1. Calculating exit capacity
                                    1. Protected corridors
                                      1. Enclosure of corridors that are not protected corridors
                                        1. Sub-division of corridors
                                          1. Cavity barriers
                                            1. External escape routes
                                            2. Small premises
                                              1. General
                                                1. Construction
                                                  1. Distance of travel and number of escape routes
                                                  2. Residential care homes
                                                    1. General
                                                      1. Planning for progressive horizontal evacuation
                                                        1. Fire detection
                                                          1. Bedrooms
                                                            1. Door-closing devices
                                                              1. Sprinkler systems

                                                              Introduction

                                                              3.1The general principle to be followed when designing facilities for means of escape is that any person confronted by an outbreak of fire within a building can turn away from it and make a safe escape. This Section deals with the provision of means of escape from any point to the storey exit of the floor in question, for all types of building. It should be read in conjunction with the guidance on the vertical part of the escape route in Section 4 and the general provisions in Section 5.

                                                              It should be noted that guidance in this Section is directed mainly at smaller, simpler types of buildings. Detailed guidance on the needs of larger, more complex or specialised buildings, can be found elsewhere (see paragraphs 0.21 to 0.35).

                                                              It should also be noted that although most of the information contained in this Section is related to general issues of design, special provisions apply to the layouts of certain institutional buildings (see paragraphs 3.38 onwards).

                                                              In the case of small shop, office, industrial, storage and other similar premises (ones with no storey larger than 280m2 and having no more than 2 storeys plus a basement storey), the guidance in paragraph 3.32 to 3.37 may be followed instead of the other provisions in this Section.

                                                              Escape route design

                                                              Number of escape routes and exits

                                                              3.2The number of escape routes and exits to be provided depends on the number of occupants in the room, tier or storey in question and the limits on travel distance to the nearest exit given in Table 2.

                                                              Notes:It is only the distance to the nearest exit that should be so limited. Any other exits may be further away than the distances in Table 2.

                                                              3.3In multi-storey buildings (see Section 4) more than one stair may be needed for escape, in which case every part of each storey will need to have access to more than one stair. This does not prevent areas from being in a dead-end condition provided that the alternative stair is accessible in case the first one is not usable.

                                                              3.4In mixed-use buildings, separate means of escape should be provided from any storeys (or parts of storeys) used for Residential or Assembly and Recreation purposes.

                                                              Single escape routes and exits

                                                              3.5In order to avoid occupants being trapped by fire or smoke, there should be alternative escape routes from all parts of the building.

                                                              However a single route is acceptable for:

                                                              • aparts of a floor from which a storey exit can be reached within the travel distance limit for travel in one direction set in Table 2 (see also paragraph 3.7). This is provided that, in the case of places of assembly and bars, no one room in this situation has an occupant capacity of more than 60 people or 30 people if the building is in Institutional use (Purpose Group 2a). The calculation of occupant capacity is described in Appendix C; or
                                                              • ba storey with an occupant capacity of not more than 60 people, where the limits on travel in one direction only are satisfied (see Table 2).

                                                              3.6 In many cases there will not be an alternative at the beginning of the route. For example, there may be only one exit from a room to a corridor, from which point escape is possible in two directions. This is acceptable provided that the overall distance to the nearest storey exit is within the limits for routes where there is an alternative and the ‘one direction only’ section of the route does not exceed the limit for travel where there is no alternative, see Table 2. Diagram 10 shows an example of a dead-end condition in an open storey layout.

                                                              Access control measures

                                                              Table 2

                                                              3.7Measures incorporated into the design of a building to restrict access to the building or parts of it should not adversely affect fire safety provisions.

                                                              Whilst it may be reasonable to secure some escape routes outside normal business hours, the measures left in place should be sufficient to allow safe evacuation of any persons left inside the building (see paragraph 5.11).

                                                              Number of occupants and exits

                                                              Table 3

                                                              3.8The figure used for the number of occupants will normally be that specified as the basis for the design. When the number of occupants likely to use a room, tier or storey is not known, the capacity should be calculated on the basis of the appropriate floor space factors. Guidance for this is set out in Appendix C. Table 3 gives the minimum number of escape routes and exits from a room or storey according to the number of occupants. (This number is likely to be increased by the need to observe travel distances and by other practical considerations.) The width of escape routes and exits is the subject of paragraph 3.18.

                                                              Alternative escape routes

                                                              Diagram 11

                                                              3.9A choice of escape routes is of little value if they are all likely to be disabled simultaneously. Alternative escape routes should therefore satisfy the following criteria:

                                                              • athey are in directions 45deg or more apart (see Diagram 11); or
                                                              • b they are in directions less than 45deg apart, but are separated from each other by fire-resisting construction.

                                                              Inner rooms

                                                              Diagram 12

                                                              3.10A room from which the only escape route is through another room is called an inner room. It is at risk if a fire starts in the other room, called the access room (see Diagram 12).

                                                              Such an arrangement is only acceptable if the following conditions are satisfied:

                                                              • ahe occupant capacity of the inner room should not exceed 60 (30 in the case of a building in purpose group 2a (Institutional));
                                                              • bthe inner room should not be a bedroom;
                                                              • cthe inner room should be entered directly off the access room (but not via a corridor);
                                                              • dthe escape route from the inner room should not pass through more than one access room;
                                                              • ethe travel distance from any point in the inner room to the exit(s) from the access room should not exceed the appropriate limit given in Table 2;
                                                              • fthe access room should not be a place of special fire hazard and should be in the control of the same occupier; and
                                                              • gone of the following arrangements should be made:
                                                                • ithe enclosures (walls or partitions) of the inner room should be stopped at least 500mm below the ceiling; or
                                                                • iia suitably sited vision panel not less than 0.1m2 should be located in the door or walls of the inner room, to enable occupants of the inner room to see if a fire has started in the outer room; or
                                                                • iiithe access room should be fitted with a suitable automatic fire detection and alarm system to warn the occupants of the inner room of the outbreak of a fire in the access room.

                                                              Planning of exits in a central core

                                                              3.11Buildings with more than one exit in a central core should be planned so that storey exits are remote from one another and so that no two exits are approached from the same lift hall, common lobby or undivided corridor, or linked by any of these (see Diagram 13).

                                                              Open spatial planning

                                                              Diagram 13

                                                              3.12Escape routes should not be prejudiced by openings between floors, such as an escalator. (see Diagram 14).

                                                              An escape route should not be within 4.5m of the openings unless:

                                                              • athe direction of travel is away from the opening; or
                                                              • bthere is an alternative escape route which does not pass within 4.5m of the open connection.

                                                              Access to storey exits

                                                              3.13Any storey which has more than one escape stair should be planned so that it is not necessary to pass through one stairway to reach another. However it would be acceptable to pass through one stairway’s protected lobby to reach another stair.

                                                              Separation of circulation routes from stairways

                                                              3.14Unless the doors to a protected stairway and any associated exit passageway are fitted with an automatic release mechanism (see Appendix B, paragraph 3b), the stairway and any associated exit passageway should not form part of the primary circulation route between different parts of the building at the same level. This is because the self-closing fire doors are more likely to be rendered ineffective as a result of their constant use, or because some occupants may regard them as an impediment. For example, the doors are likely to be wedged open or have their closers removed.

                                                              Storeys divided into different uses

                                                              3.15Where a storey contains an area (which is ancillary to the main use of the building) for the consumption of food and/or drink, then:

                                                              • anot less than two escape routes should be provided from each such area (except inner rooms which meet the provisions in paragraph 3.10); and
                                                              • bthe escape routes from each such area should lead directly to a storey exit without entering any kitchen or similar area of high fire hazard.

                                                              Storeys divided into different occupancies

                                                              3.16Where any storey is divided into separate occupancies (i.e. where there are separate ownerships or tenancies of different organisations):

                                                              • athe means of escape from each occupancy should not pass through any other occupancy; and
                                                              • bif the means of escape include a common corridor or circulation space, either it should be a protected corridor, or a suitable automatic fire detection and alarm system should be installed throughout the storey

                                                              Height of escape routes

                                                              3.17All escape routes should have a clear headroom of not less than 2m except in doorways.

                                                              Width of escape routes and exits

                                                              3.18The width of escape routes and exits depends on the number of persons needing to use them. They should not be less than the dimensions given in Table 4. (Attention is also drawn to the guidance in Approved Document M Access to and Use of buildings).

                                                              3.19Where the maximum number of people likely to use the escape route and exit is not known, the appropriate capacity should be calculated on the basis of the occupant capacity. Guidance is set out in Appendix C.

                                                              3.20Guidance on the spacing of fixed seating for auditoria is given in BS 5588-6:1991.

                                                              Calculating exit capacity

                                                              Table 4

                                                              3.21If a storey or room has two or more storey exits it has to be assumed that a fire might prevent the occupants from using one of them. The remaining exit(s) need to be wide enough to allow all the occupants to leave quickly. Therefore when deciding on the total width of exits needed according to Table 4, the largest exit should be discounted. This may have implications for the width of stairs, because they should be at least as wide as any storey exit leading onto them. Although some stairs are not subject to discounting (see paragraphs 4.20 and 4.21), the storey exits onto them will be.

                                                              3.22The total number of persons which two or more available exits (after discounting) can accommodate is found by adding the maximum number of persons that can be accommodated by each exit width. For example, 3 exits each 850mm wide will accommodate 3 x 110 = 330 persons (not the 510 persons accommodated by a single exit 2550mm wide).

                                                              3.23Where a ground floor storey exit shares a final exit with a stair via a ground floor lobby, the width of the final exit should be sufficient to enable a maximum evacuation flow rate equal to or greater than that from the storey exit and stair combined (see Diagram 15).

                                                              Protected corridors

                                                              3.24A corridor which serves a part of the means of escape in any of the following circumstances should be a protected corridor:

                                                              • aevery corridor serving bedrooms;
                                                              • bevery dead-end corridor (excluding recesses and extensions not exceding 2m deep as shown in Figures 10 and 11 of BS 5588- 11:1997); and
                                                              • cany corridor common to two or more different occupancies (see also paragraph 3.16).

                                                              Enclosure of corridors that are not protected corridors

                                                              3.25 Where a corridor that is used as a means of escape, but is not a protected corridor, is enclosed by partitions, those partitions provide some defence against the spread of smoke in the early stages of a fire, even though they may have no fire resistance rating. To maintain this defence the partitions should be carried up to the soffit of the structural floor above, or to a suspended ceiling and openings into rooms from the corridor should be fitted with doors, which need not be fire doors. Open planning, while offering no impediment to smoke spread, has the compensation that occupants can become aware of a fire quickly.

                                                              Sub-division of corridors

                                                              Diagram 16

                                                              3.26If a corridor provides access to alternative escape routes, there is a risk that smoke will spread along it and make both routes impassable before all occupants have escaped.

                                                              To avoid this, every corridor more than 12m long which connects two or more storey exits, should be sub-divided by self-closing fire doors (and any necessary associated screens). The fire door(s) and any associated screen(s) should be positioned approximately mid-way between the two storey exits to effectively safeguard the route from smoke (having regard to the layout of the corridor and to any adjacent fire risks).

                                                              In a building of Purpose Groups 2 to 7, where a cavity exists above the enclosures to any such corridor, because the enclosures are not carried to full storey height or (in the case of a top storey) to the underside of the roof covering, the potential for smoke to bypass the sub-division should be restricted by:

                                                              • afitting cavity barriers on the line of the enclosure(s) to and across the corridor (see Diagram 16a); or
                                                              • bsub-dividing the storey using fire-resisting construction passing through the line of the sub-division of the corridor (see diagram 16b). Any void above this subdivision should be fitted with cavity barriers on the line of sub- division of the storey and the corridor; or
                                                              • c enclosing the cavity on the lower side by a fire-resisting ceiling which extends throughout the building, compartment or separated part.

                                                              Any door which could provide a path for smoke to bypass the sub-division should be made self closing (but need not necessarily be fire-resisting).

                                                              3.27If a dead-end portion of a corridor provides access to a point from which alternative escape routes are available, there is a risk that smoke from a fire could make both routes impassable before the occupants in the dead-end have escaped. To avoid this, unless the escape stairway(s) and corridors are protected by a pressurization system complying with BS EN 12101-6:2005, every dead-end corridor exceeding 4.5m in length should be separated by self-closing fire doors (together with any necessary associated screens) from any part of the corridor which:

                                                              • aprovides two directions of escape (see Diagram 17(a)); or
                                                              • bcontinues past one storey exit to another (see Diagram 17(b)).

                                                              Cavity barriers

                                                              3.28Additional measures to safeguard escape routes from smoke are given in Section 9 (B3).

                                                              External escape routes

                                                              Diagram 17

                                                              3.29Guidance on the use of external escape stairs from buildings is given in paragraph 4.44.

                                                              3.30Where an external escape route (other than a stair) is beside an external wall of the building, that part of the external wall within 1800mm of the escape route should be of fire- resisting construction, up to a height of 1100mm above the paving level of the route. For guidance on external escape stairs see paragraph 5.25.

                                                              3.31If more than one escape route is available from a storey, or part of a building, one of those routes may be by way of a flat roof, provided that:

                                                              • athe route does not serve an Institutional building, or part of a building intended for use by members of the public; and
                                                              • bit meets the provisions in paragraph 5.35.

                                                              Small premises

                                                              3.32In small premises, as described in paragraph 3.33, the number of persons is generally limited and the size of the premises, when undivided, will tend to enable clear vision of all parts. Therefore the occupants will be able to quickly reach an entrance/exit in an emergency. Thus a reduction in the number of exits and stairs as set out in paragraphs 3.33 to 3.37, 4.6 and 4.33 is acceptable. However, where the sale, storage or use of highly flammable materials is involved, it is necessary for persons to rapidly vacate the premises in the event of a fire. To facilitate this, the general guidance in paragraph 3.33 would not apply.

                                                              General

                                                              3.33The following paragraphs apply in place of only those provisions relating to the number and positioning of exits and protected stairways and measurement of distances of travel.

                                                              • aThe premises should be in a single occupancy and should not comprise more than a basement, a ground floor and a first storey. No storey should have a floor area greater than 280m2 (see Diagram 18);
                                                              • bAny kitchen or other open cooking arrangement should be sited at the extremity of any dead end remote from the exit(s); and
                                                              • cThe planned seating accommodation or the assessed standing accommodation (see Table C1) for small premises comprising a bar or restaurant should not exceed 30 persons per storey. This figure may be increased to 100 persons for the ground storey if that storey has an independent final exit.

                                                              Notes:They do not apply to premises used principally for the storage and/or sale of highly flammable liquids or materials.
                                                              In covered shopping complexes, the size of small units that may be served by a single exit is further restricted. This is dealt with in BS 5588- 10:1991.

                                                              Construction

                                                              Diagram 18

                                                              3.34The floor areas should be generally undivided (except for kitchens, ancillary offices and stores) to ensure that exits are clearly visible from all parts of the floor areas.

                                                              3.35Store rooms should be enclosed with fire-resisting construction.

                                                              3.36 Sufficient clear glazed areas should be provided in any partitioning separating a kitchen or ancillary office from the open floor area to enable any person within the kitchen or office to obtain early visual warning of an outbreak of fire. Alternatively, an automatic fire detection and alarm system may be provided in the outer room.

                                                              Notes:The clear glazed area or vision panel may need to be provided for other reasons.

                                                              Distance of travel and number of escape routes

                                                              Table 5

                                                              3.37 The escape routes from any storey should be of such a number and so situated that the distance of travel from any point to the nearest storey exit does not exceed the appropriate limits set out in Table 5.

                                                              Notes:The distance of travel in small premises with an open stairway is measured to the foot of the stair in a basement or to the head of the stair in a first storey see paragraph 4.33.
                                                              The siting of two or more exits or stairs should be such that they afford effective alternative directions of travel from any relevant point in a storey.

                                                              Residential care homes

                                                              General

                                                              3.38 Residential care homes are quite diverse and can be used by a variety of residents, often requiring different types of care to suit their specific needs. They can include homes for the elderly, children and people who are physically or mentally disabled. The choice of fire safety strategy is dependent upon the way a building is designed, furnished, staffed and managed and the level of dependency of the residents.

                                                              3.39 Generally, in care homes for the elderly it is reasonable to assume that at least a proportion of the residents will need some assistance to evacuate. As such these buildings should be designed for progressive horizontal evacuation (PHE) in accordance with paragraphs 3.41 to 3.52 below. For other types of care home a judgement should be made as to whether PHE or a simultaneous evacuation strategy is appropriate. Whatever approach is adopted in the design of a building this must be recorded and communicated to the building management to ensure that procedures are adopted that are compatible with the building design.

                                                              3.40The guidance on PHE given in paragraphs 3.41 to 3.52 is for those care homes, to which the provisions of the “Firecode” documents are not applicable (see Para 0.23).

                                                              Planning for progressive horizontal evacuation

                                                              Diagram 19

                                                              3.41The concept of PHE requires those areas used for the care of residents to be subdivided into protected areas separated by compartment walls and compartment floors. This allows horizontal escape to be made by evacuating into adjoining protected areas. The objective is to provide a place of relative safety within a short distance, from which further evacuation can be made if necessary but under less pressure of time.

                                                              3.42Each storey, used for the care of residents, should be divided into at least three protected areas by compartment walls and all floors should be compartment floors.

                                                              3.43Every protected area should be provided with at least two exits to adjoining, but separate protected areas. Travel distances within a protected area to these exits should not exceed those given in Table 2. The maximum travel distance from any point should be not more than 64m to a storey exit or a final exit.

                                                              3.44A fire in any one protected area should not prevent the occupants of any other area from reaching a final exit (see Diagram 19). Escape routes should not pass through ancillary accommodation such as that listed in paragraph 3.50.

                                                              3.45The number of residents’ beds in protected areas should be established based on assessment of the number of staff likely to be available and the level of assistance that residents may require. In no case should this exceed 10 beds in any one protected area.

                                                              3.46Adjoining protected areas into which horizontal evacuation may take place should each have a floor area sufficient to accommodate not only their own occupants but also the occupants from the largest adjoining protected area.

                                                              Fire detection

                                                              3.47A fire detection and alarm system should be provided to an L1 standard in accordance with BS 5839-1:2002.

                                                              Bedrooms

                                                              p>3.48Each bedroom should be enclosed in fire-resisting construction with fire resisting doors and every corridor serving bedrooms should be a protected corridor (see paragraph 3.24).

                                                              3.49Bedrooms should not contain more than one bed (this includes a double bed)

                                                              3.50Ancillary accomodation such as the following, should be enclosed by fire-resisting construction.

                                                              • achemical stores;
                                                              • bcleaners’ rooms;
                                                              • cclothes’ storage;
                                                              • dday rooms;
                                                              • esmoking rooms;
                                                              • fdisposal rooms;
                                                              • gplant rooms;
                                                              • hlinen stores;
                                                              • ikitchens;
                                                              • jlaundry rooms;
                                                              • kstaff changing and locker rooms; and
                                                              • lstore rooms.

                                                              Door-closing devices

                                                              3.51The specification of door-closing devices for fire doors should take account of the needs of residents. In particular where self-closing doors could present an obstacle to the residents of the building then the following hardware in accordance with BS EN 1155:1997 would be appropriate;

                                                              • Bedroomsfree-swing door closers.
                                                              • Circulation spaceshold-open devices.

                                                              Sprinkler systems

                                                              3.52Where a sprinkler system is provided in accordance with paragraph 0.16. The following variations to the guidance given in paragraphs 3.41 to 3.51 are acceptable,

                                                              • aFire doors to bedrooms need not be fitted with self closing devices.
                                                              • bProtected areas may contain more than 10 beds.
                                                              • cBedrooms may contain more than one bed.
                                                                Note: Management procedures will need to take account of the larger number of residents that may need assistance and the need to manually close bedroom doors during sleeping hours.