2.2 Separation
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Buildings or parts of a building in different occupation pose particular problems in terms of fire safety. This is because one occupier usually does not have any control over the activities or working practices of their co-occupiers and in such cases, separating walls and separating floors are recommended.
The intention of separation is to limit fire growth and thereby give adjoining occupiers more time to escape before they are threatened by fire or smoke.
Enclosed shopping centres - due to the special fire precautions within enclosed shopping centres, additional guidance is grouped in the annex 2.C. The intention is to help designers and verifiers find the information they require quickly when designing or vetting such buildings. However it is important to remember that the guidance in the annexes is in addition and supplementary to the guidance to Standards 2.1 to 2.15.
Conversions - in the case of conversions, as specified in regulation 4, the building as converted shall meet the requirements of this standard in so far as is reasonably practicable, and in no case be worse than before the conversion (regulation 12, schedule 6).
2.2.1 Separating walls and separating floors
Separating walls and separating floors should have at least a medium fire resistance duration (see annex 2.D). However there are some situations where the wall or floor will demand a greater fire resistance. For example, where the separating floor is also an element of structure in a building where the topmost storey is at a height of more than 18m, long fire resistance duration would be necessary in most cases (see clause 2.1.1).
A separating wall or separating floor should be provided between parts of a building where they are in different occupation.
Multi-occupied building - however it is possible to have no separating walls or separating floors between the different occupiers of a multi-occupied building when the building is under a single management regime. For example, multi-occupied offices with a shared reception and sanitary facilities may be regarded as being in the same occupation. In such cases, the building should have a common fire alarm system/evacuation strategy and the same occupancy profile (see clause 2.9.3). This philosophy is in effect very similar to individual departments within one large organisation. However where each unit is under the control of an individual tenant, employer or self-employed person, separating walls and separating floors should be provided between the areas intended for different occupation.
Where a speculative development is intended to be multi-occupied but the extent of management control is not known, the building should be regarded as being occupied by different persons.
2.2.3 Building with common occupation
A separating wall or separating floor with a medium fire resistance duration should be provided between parts of a building where one part is in single occupation and the other is in communal occupation. However this is not necessary between:
part of a building in single occupation and a common external stair, access balcony or access deck
a shop and a mall (see annex 2.C).
Every part of a separating wall or separating floor (other than a floor finish such as laminate flooring) should be of products that which achieve European Classification A1 or A2. However this is not necessary where the building does not have any storey at a height of more than 18m and the separation is between:
a shop or office and a dwelling above the shop or office in the same occupation where there is no other dwelling above the shop or office, and the area of the shop or office is not more than 1½ times the area of the separating floor, or
units of shared residential accommodation, or
a dwelling and a unit of shared residential accommodation.
To reduce the risk of a fire starting within a combustible separating wall or a fire spreading rapidly on or within the wall construction:
insulation exposed in a cavity should be constructed from products which achieve European Classification A1, A2 or B (see annex 2.E), and
the internal wall lining should be constructed from products which achieve European Classification A1, A2, or B, and
the wall should contain no pipes, wires or other services.
Where an element of structure (see clause 2.3.0) provides support to a separating wall or separating floor, constructed from products which achieve European Classification A1 or A2, the supporting element of structure should also achieve European Classification A1 or A2.
Where an element of structure provides support to a separating wall or separating floor which attracts a higher period of fire resistance, the supporting element of structure should have at least the same period of fire resistance.
Guidance on the fire protection of openings and service penetrations is provided in clause 2.1.14. However self-closing fire doors should not be installed in separating walls other than in the situation described in clause 2.2.3 or where the building is in the same occupation but in different use. A fire shutter should not be installed in a separating wall or separating floor.
Where a separating wall or separating floor meets an external wall, another separating wall, a compartment wall or any other wall or screen used to protect routes of escape (see clause 2.0.6), the junction should maintain the fire resistance duration of the separating wall or separating floor. Where a separating wall forms a junction with a roof or a fire resisting ceiling (see clause 2.1.16), the junction should be constructed in accordance with the recommendations in clause 2.1.15.
Where a separating wall or floor abuts a structure containing a cavity, a fire barrier should be installed in the cavity so as to extend the line, and maintain the fire resistance, of the wall or floor. However this is not necessary where the cavity is formed by two leaves of masonry or concrete at least 75mm thick and the external wall is provided with cavity barriers around all openings and at the top of the wall-head.
Where an external wall cladding system has achieved the performance levels in BR 135 ‘Fire Performance of external thermal insulation for walls of multi-storey buildings’ when read in conjunction with the test methodology in BS 8414: Part 1: 2015+A1: 2017 or BS 8414: Part 2: 2015+A1: 2017, the junction detail is considered to meet the intent of Standard 2.1. BS 9414: 2019 (Draft June 2019) provides additional information on the application of results from BS 8414 tests.