What is class S pipe bedding?
Class S pipe bedding is a full granular bed and surround: the pipe sits on granular material and is completely enclosed by it. It is a UK bedding class, described in BS 9295, and is typically used for flexible pipes such as thermoplastic. Depths and material vary by agency, so check the project's standard detail.
Class S bedding vs class B bedding
Edinburgh's standard detail 5001 shows the difference: Type B is a granular bed and haunch for rigid pipes such as vitrified clay and precast concrete, and Type S is a granular bed and surround for non-rigid pipes such as thermoplastic. Classes such as B use significantly less material than a full surround.
Class S pipe bedding on US projects
US specifications often describe embedment differently, for example the ASTM D2321 soil classes for thermoplastic sewer pipe. When a plan calls for class S, take the bed depth, the surround height above the crown and the material from the agency's detail, then enter them in the pipe bedding calculator.
Sources
Checked 2026-11-02.