Items where Subject is "Section 8: Cavities – flats"

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ADB1 2019 Para:8.1 Section 8: Cavities – flats

Cavities in the construction of a building provide a ready route for the spread of smoke and flame, which can present a greater danger as any spread is concealed. For the purpose of this document, a cavity is considered to be any concealed space.


ADB1 2019 Para:8.1 Diagram 8.1 Provisions for cavity barriers

Fire-stopping (same resistance as compartment)
Cavity barriers
1. See paragraph 8.5
See para 8.2


ADB1 2019 Para:8.2 Provision of cavity barriers

To reduce the potential for fire spread, cavity barriers should be provided for both of the following.
a. To divide cavities.
b. To close the edges of cavities.
See Diagram 8.1. Cavity barriers should not be confused with fire-stopping details (Section 9).


ADB1 2019 Para:8.2 Diagram 8.2 Cavity walls excluded from provisions for cavity barriers

1. Materials used to close the cavity in this arrangement do not need to achieve a specific performance in relation to fire resistance.
2. Domestic meter cupboards may be installed provided that the following conditions are met:
a. There are no more than two cupboards per dwelling
b. The openings in the outer wall leaf are not bigger than 800X500mm for each cupboard
c. The inner leaf is not penetrated except by a sleeve not more than 80X80mm, which is fire-stopped.
3. Materials achieving class B-s3, d2 or worse may be placed within the cavity.
See para 8.3


ADB1 2019 Para:8.3 Diagram 8.3 Fire resisting ceiling below concealed space

The ceiling should meet the following conditions.
a. Provide a minimum fire resistance of EI 30.
b. Be imperforate, except for an opening described in paragraph 5.24.
c. Extend through out the building or compartment.
d. Not be easily demountable.
See para 8.5


ADB1 2022 Para:8.3 Junctions and edges of cavities

Cavity barriers should be provided at all of the following locations.
a. At the edges of cavities, including around openings (such as windows, doors and exit/entry points for services).
b. At the junction between an external cavity wall and every compartment floor and compartment wall.
c. At the junction between an internal cavity wall and every compartment floor, compartment wall or other wall or door assembly forming a fire resisting barrier.
This does not apply where a wall meets the conditions of Diagram 8.2.

Department for Communities and Local Government, (2019) Pathways around fire-separating elements Junctions and cavity closures. In: Approved Document B: Fire Safety - Volume 1: Dwellings. 2019 ed. Section 8: Cavities – flats, 1 (8.3). RIBA Publishing Publication, London, p. 65. ISBN 9781859469156

ADB1 2019 Para:8.4 Diagram 8.4 Provisions for cavity barriers in double-skinned insulated roof sheeting

The insulation should make contact with both skins of sheeting. See also Diagram 5.2a regarding the need for fire-stopping where such roofs pass over the top of a compartment wall.
See para 8.7


ADB1 2019 Para:8.5 Protected escape routes

If the fire resisting construction of a protected escape route is either of the following.
a. Not carried to full storey height.
b. At the top storey, not carried to the underside of the roof covering.
Then the cavity above or below the fire resisting construction should be either of the following.
i. Fitted with cavity barriers on the line of the enclosure.
ii. For cavities above the fire resisting construction, enclosed on the lower side by a fire resisting ceiling (minimum EI 30) that extends throughout the building, compartment or separated part (see Diagram 8.3).


ADB1 2019 Para:8.6 Cavities affecting alternative escape routes

In divided corridors (paragraph 3.25 and following) with cavities, fire-stopping should be provided to prevent alternative escape routes being affected by fire and/or smoke.


ADB1 2019 Para:8.7 Double-skinned corrugated or profiled roof sheeting

Cavity barriers are not required between double-skinned corrugated or profiled insulated roof sheeting, if the sheeting complies with all of the following.
a. The sheeting is rated class A2-s3, d2 or better.
b. Both surfaces of the insulating layer are rated class C-s3, d2 or better.
c. Both surfaces of the insulating layer make contact with the inner and outer skins of cladding (Diagram 8.4).


ADB1 2019 Para:8.8 Construction and fixings for cavity barriers

Cavity barriers, tested from each side separately, should provide a minimum of both of the following:
a. 30 minutes’ integrity (E 30)
b. 15 minutes’ insulation (I 15).
They may be formed by a construction provided for another purpose if it achieves the same performance.


ADB1 2022 Para:8.9 Construction and fixings for cavity barriers

Cavity barriers should meet the requirements set out in paragraphs 5.21 to 5.24.

Department for Communities and Local Government, (2019) Construction and fixings for cavity barriers. In: Approved Document B: Fire Safety - Volume 1: Dwellings. 2019 ed. Section 8: Cavities – flats, 1 (8.9). RIBA Publishing Publication, London, p. 68. ISBN 9781859469156

This list was generated on Wed Aug 17 12:41:28 2022 UTC.