This Part of BS 4255 specifies requirements for the classification, physical properties and marking of solid (non-cellular) rubber used in preformed gaskets for sealing applications in buildings where resistance to weathering, ozone and permanent deformation under load are of prime importance.

This Part applies to chloroprene, butyl, halobutyl, ethylene propylene, chlorosulphonated polyethylene and silicone rubbers used in the gaskets.

Five classes of material, defined according to the hardness of the rubber, are specified.