DESIGN PROCESS
Note: services may also penetrate the cavity barrier/s and these penetration seals must be a fire- tested system. Typical examples of penetrations passing through the through-wall are illustrated here.
Mechanical waste heat recovery (MWHR) services penetration
Metal conduit and BIB tap penetration
The following definitions are used in Approved Document B in England to differentiate between cavity barriers and firestopping. Cavity barrier A construction within a cavity, other than a smoke curtain, to perform either of the following functions: • Close a cavity to stop smoke or flame entering • Restrict the movement of smoke or flame within a cavity. Firestopping A seal provided to close an imperfection of fit or design tolerance between elements or components, to restrict the spread of fire and smoke. Where cavity barriers interface with the through-wall, they should be mechanically fixed to a through-wall cavity face. The through-wall system should also have equal or better fire resistance to the cavity barrier when tested from the cavity side.
DESIGN LIFE/DURABILITY
CORROSION The effects of corrosion of the SFS metalwork should be considered by the designer in collaboration with the system owner. The following factors should be considered: • Coastal environments • Below damp-proof course level in residential buildings. NHBC guidance requires either enhanced galvanised specification to z600 grade or SFS to be constructed on top of concrete upstands. • When using concrete upstands, cold bridging should be considered.
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