Section 2: Design for horizontal escape

Introduction

2.1 Means of escape should be provided from any point on a storey to the storey exit, for all types of building. The general principle is that any person confronted by a fire within a building can turn away from it and escape safely.

2.2 For small shop, office, industrial, storage and other similar premises, the guidance on small premises (see section 4) may be followed instead of the provisions in this section, if they meet both of the following conditions.

a. No storey has an area more than 280m2.

b. There is a maximum of two storeys plus a basement storey.

Escape route design

Number of escape routes and exits

2.3 The number of escape routes and exits that should be provided depends on both of the following.

a. The number of occupants in the room, tier or storey.

b. The limits on travel distance to the nearest exit given in Table 2.1 (which apply only to the nearest exit; other exits may be further away).

2.4 In multi-storey buildings, if more than one stair is needed for vertical escape, every part of each storey should have access to more than one stair. An area may be in a dead end provided the alternative stair is accessible.

2.5 In mixed use buildings, separate means of escape should be provided from any storeys or parts of storeys used for the ‘residential’ or ‘assembly and recreation’ purpose groups (purpose groups 1, 2 and 5).

Single escape routes and exits

2.6 A single escape route is acceptable for either of the following.

a. Parts of a floor from which a storey exit can be reached within the limit for travel distance in one direction shown in Table 2.1 (see also paragraph 2.8), provided the following apply.

i. For places of assembly and bars, no one room in this situation has more than 60 people.

ii. For ‘residential (institutional)’ buildings (purpose group 2(a)), no one room in this situation has more than 30 people. Occupant number calculations are described in Appendix D.

b. A storey with no more than 60 people, where the limits on travel distance in one direction only are satisfied (see Table 2.1).

2.7 In many cases, the beginning of a route will not have an alternative escape route (for example, a single exit from a room into a corridor where escape is possible in two directions). This is acceptable if both of the following apply.

a. The travel distance to the nearest storey exit is within the limits for routes where escape is possible in more than one direction (Table 2.1).

b. The travel distance for the ‘one direction only’ section of the route does not exceed the limit for travel distance where there is no alternative escape route (Table 2.1).

Diagram 2.1 shows how to measure travel distances from a dead end in an open storey layout.

Access control measures

2.8 Measures to restrict access to the building (or parts of it) should not adversely affect fire safety provisions. It may be reasonable to close some escape routes outside normal business hours, but measures should remain to safely evacuate people left inside the building (see paragraph 5.6).

Number of occupants and exits

2.9 The building design should be based on the number of occupants. If the number is not known, use the appropriate floor space factors (Appendix D).

Table 2.2 gives the minimum number of escape routes and exits from a room or storey for different numbers of occupants. This number is likely to be increased by the need to observe travel distances and other practical considerations.

The width of escape routes and exits is given in paragraph 2.18.

Alternative escape routes

2.10 Alternative escape routes should satisfy one of the following criteria.

a. They are in directions 45 degrees or more apart (Diagram 2.2).

b. They are in directions less than 45 degrees apart, but separated from each other by fire resisting construction.

Inner rooms

2.11 An inner room is at risk if a fire starts in the access room (Diagram 2.3). Such an arrangement should only be accepted if all of the following conditions are satisfied.

a. The occupant number of the inner room does not exceed:

i. 30 people for ‘residential (institutional)’ buildings (purpose group 2(a))

ii. 60 people for other purpose groups.

b. The inner room is not a bedroom.

c. The inner room is entered directly from the access room (but not via a corridor).

d. The escape route from the inner room does not pass through more than one access room.

e. The travel distance from any point in the inner room to the exits from the access room does not exceed the distances in Table 2.1.

f. The access room meets both of the following conditions.

i. It is not a place of special fire hazard.

ii. It is in the control of the same occupier.

g. One of the following arrangements is made.

i. The enclosures (walls or partitions) of the inner room stop a minimum of 500mm below the ceiling.

ii. The door or walls of the inner room contain a vision panel (minimum 0.1m2), so people can see if a fire starts in the access room.

iii. The access room is fitted with an automatic fire detection and alarm system to warn occupants of the inner room if a fire starts in the access room.

Planning of exits in a central core

2.12 Where a central core has more than one exit, storey exits should be remote from one another and no two exits should be approached from the same lift hall, common lobby or undivided corridor (Diagram 2.4).

Open spatial planning

2.13 Escape routes should not be within 4.5m of openings between floors, such as for an escalator, unless either of the following applies.
a. The direction of travel is away from the opening.
b. An alternative escape route does not pass within 4.5m of the open connection (Diagram 2.5).

Access to storey exits

2.14 Where a storey has more than one escape stair, it should be planned so that it is not necessary to pass through one stair to reach another. However, it would be acceptable to pass through one stair’s protected lobby to reach another stair.

Separation of circulation routes from protected stairways

2.15 Where they serve protected stairways that are part of primary circulation routes, self-closing fire doors should be fitted with an automatic release mechanism, to avoid them being rendered ineffective by misuse. Otherwise, the stair (and any associated exit passageway) should not form part of the primary circulation route between different parts of the building at the same level.

Storeys divided into different uses

2.16 If a storey contains areas for consuming food and/or drink, and where that is not the main use of the building, then both of the following apply.

a. A minimum of two escape routes should be provided from each area, except from inner rooms that meet the conditions in paragraph 2.11.

b. Those escape routes should lead directly to a storey exit without entering a kitchen or similar area of high fire hazard.

Storeys divided into different occupancies

2.17 Where a storey is divided into areas of occupancy under separate ownership or tenancy, then both of the following apply.

a. The means of escape from each occupancy should not pass through any other occupancy.

b. If a common corridor or circulation space is on the escape route, one of the following should apply.

i. It should be a protected corridor.

ii. A suitable automatic fire detection and alarm system should be installed throughout the storey.

Width of escape routes and exits

2.18 The width of escape routes and exits should meet the provisions in Table 2.3, as well as the guidance in Approved Document M.

2.19 If the maximum number of people likely to use the escape route and exit is not known, it should be calculated using the occupant number guidance in Appendix D.

2.20 Guidance on the spacing of fixed seating for auditoria is given in Annex D of BS 9999.

Calculating exit capacity

2.21 Where multiple storey exits are available, fire might prevent one from being used. Remaining exits need to be wide enough for all occupants, so when using Table 2.3, the largest exit should be discounted.

Stairs should be at least as wide as any storey exit leading onto them. While some stairs are not subject to discounting (paragraphs 3.14 and 3.15), because the stairs will be available for other floors, the storey exits onto them are.

2.22 To calculate how many people two or more available exits (after discounting) can accommodate, add together the maximum numbers of people that each exit width can accommodate.

For example, three exits each 850mm wide accommodate 33110 = 330 people.

2.23 If a ground floor storey exit and a stair share a final exit (via a ground floor lobby), then the final exit should be wide enough to evacuate people at a maximum flow rate equal to or greater than from the storey exit and stair combined (Diagram 2.6).

This can be calculated using the following formula:

W = ((N/2.5) + (60S))/80

where:

W is the width of final exit in metres

N is the number of people served by ground floor storey exit S is the stair width in metres.

If the number of people (N) entering the lobby from the ground storey is more than 60, then the distance from the foot of the stair or the storey exit to the final exit should be a minimum of 2m (see Diagram 2.6).

If that minimum distance cannot be achieved, the width of the final exit (W) should be at least the width of the stair plus the width of the storey exit.

Worked example

A ground floor storey exit serving 250 people shares a common final exit with a 1.2m wide stair. Required final exit width = ((250/2.5) + (1.2360))/80 = 2.150m

Protected corridors

2.24 A corridor serving as part of the means of escape in any of the following circumstances should be a protected corridor.

a. Every corridor that serves bedrooms.

b. Every dead-end corridor (excluding recesses and extensions a maximum of 2m deep, as shown in Diagrams 2.7 and 2.8).

c. Any corridor shared by two or more occupancies (paragraph 2.17).

Enclosure of corridors that are not protected corridors

2.25 If a corridor is used for a means of escape but is not a protected corridor, even though the enclosing partitions may have no fire resistance, both of the following should be met to inhibit the spread of smoke.

a. Partitions should continue to the soffit of the structural floor above, or to a suspended ceiling.

b. Openings into rooms from the corridor should be fitted with doors, which do not need to be fire doorsets.
Open planning will not inhibit the spread of smoke, but occupants can become aware of a fire quickly.

Division of corridors

2.26 A corridor providing access to alternative escape routes should be divided by fire doorsets fitted with a self-closing device (and associated screens) where both of the following apply.

a. It is more than 12m long.

b. It connects two or more storey exits.

The fire doorsets (including any screens) should be approximately mid-way between the two storey exits. They should safeguard the route from smoke, while considering the layout of the corridor and any adjacent fire risks.

2.27 For buildings other than dwellings (purpose groups 2 to 7): if a cavity exists above the enclosures to a corridor as described above (because the enclosures are not carried to full storey height or the underside of the roof covering at the top storey), the potential for smoke to bypass the enclosure should be restricted by one of the following methods.

a. Method 1 – Fitting cavity barriers on the line of the enclosure(s) to and across the corridor (Diagram 2.9).

b. Method 2 – Dividing the storey using fire resisting construction that passes through the line of the division of the corridor (Diagram 2.9). Any cavity above this division should be fitted with cavity barriers on the line of division of the storey and the corridor.

c. Method 3 – Enclosing the cavity on the lower side by a fire resisting ceiling that extends throughout the building, compartment or separated part.
Any door that could provide a path for smoke to bypass the division should be fitted with a self- closing device (but need not necessarily be fire resisting).

2.28 Where dead ends of corridors exceeding 4.5m long provide access to a point from which alternative escape routes are available, they should be separated by self-closing fire doorsets (together with any associated screens) from any part of the corridor that either:

a. Provides two directions of escape (Diagram 2.10a)

b. Continues past one storey exit to another (Diagram 2.10b).

Alternatively, the stairs and corridors may be protected by a pressurisation system complying with BS EN 12101-6.

Cavity barriers

2.29 Additional measures to safeguard means of escape from smoke are given in Section 10.

External escape routes

2.30 Where an external escape route is beside an external wall of the building, the external wall should be of fire resisting construction in both of the following zones.

a. Within 1800mm of the escape route.

b. Up to 1100mm above the surface of the escape route.

This does not apply to external escape stairs (see paragraph 3.32).

Escape over flat roofs

2.31 Where a storey or part of a building has multiple escape routes available, one may be over a flat roof if it does not serve a ‘residential (institutional)’ (purpose group 2(a)) building, or part of a building intended for use by members of the public.

2.32 Where an escape route over a flat roof is provided, the roof should comply with all of the following.

a. It should be part of the same building from which escape is being made.

b. The route across the roof should lead to a storey exit or external escape route.

c. The part of the roof forming the escape route and its supporting structure, together with any opening within 3m of the escape route, should be fire resisting (minimum REI 30).

d. The route should be clearly defined and guarded by walls and/or protective barriers to protect from falling.

Residential care homes

General provisions

2.33 The choice of fire safety strategy depends on the way a building is designed, furnished, staffed and managed, and on the level of dependency of the residents.

2.34 In care homes for the elderly, some or all residents are likely to need help to evacuate. Buildings should generally be designed for progressive horizontal evacuation (PHE) in accordance with paragraphs 2.35 to 2.46.

For other care home types, the most appropriate of either a PHE or simultaneous evacuation strategy should be identified. The approach adopted in the design of a building must be recorded and communicated to the building management team, who can adopt procedures compatible with the building design.

Planning for progressive horizontal evacuation

2.35 The guidance below on PHE is for care homes where the provisions of the Firecode documents do not apply (see paragraph 0.10).

PHE requires areas used for the care of residents to be divided into protected areas by compartment walls and compartment floors. Protected areas provide a place of relative safety, from which further evacuation can be made if necessary.

2.36 Each storey used for the care of residents should be divided by compartment walls into at least three protected areas. All floors should be compartment floors.

2.37 Every protected area should have a minimum of two exits to adjoining protected areas. Maximum travel distances within a protected area should be both of the following.

a. To the exit to the adjoining protected area: as shown in Table 2.1.

b. From any point to a storey exit or a final exit: 64m.

2.38 A fire in one protected area should not prevent occupants of other areas from reaching a final exit (Diagram 2.11). Escape routes should not pass through ancillary accommodation listed in paragraph 2.44.

2.39 The number of residents’ beds in protected areas should be based on an assessment of both of the following.

a. The number of staff likely to be available.

b. The level of assistance that residents may require.

The maximum number of residents’ beds in one protected area should not exceed 10, but may need to be lower depending on the assessment.

2.40 A protected area used for horizontal evacuation from an adjoining protected area should have a floor area able to accommodate its own occupants plus those from the largest adjoining protected area.

Fire detection and alarm

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

Bedrooms

2.42 Each bedroom in a care home should be enclosed in fire resisting construction (minimum REI 30) with fire resisting doors (minimum E 30). Every corridor serving bedrooms should be a protected corridor (see paragraph 2.24).

2.43 Bedrooms should not contain more than one single or double bed.

Ancillary accommodation

2.44 Ancillary accommodation such as all of the following should be enclosed by fire resisting construction (minimum REI 30).

a. Chemical stores.

b. Cleaners’ rooms.

c. Clothes storage.

d. Day rooms.

e. Smoking rooms.

f. Disposal rooms.

g. Plant rooms.

h. Linen stores.

i. Kitchens.

j. Laundry rooms.

k. Staff changing and locker rooms.

l. Store rooms.

Door closing devices

2.45 If doors fitted with a self-closing device could present an obstacle to residents, the following hardware in accordance with BS EN 1155 is appropriate.

a. Bedrooms: free-swing door closers.

b. Circulation spaces: hold-open devices.

Sprinkler systems

2.46 When a sprinkler system is provided in accordance with Appendix E, the following variations to the guidance given in paragraphs 2.35 to 2.45 are acceptable.

a. Fire doorsets to bedrooms do not need to be fitted with self-closing devices.

b. Protected areas may contain more than 10 beds.

c. Bedrooms may contain more than one bed.

If any of the variations are made, the management procedures should take account of the larger number of residents that may need assistance, and the need to manually close bedroom doors during sleeping hours.