Type B Filter Material is a granular material used for bedding, haunching, and surrounding pipes in construction applications.
The grading requirements are set out in series 500 drainage and service ducts of the specification for highway works.
Type B Filter Material consists of natural and/or recycled coarse aggregates that comply with the standards set out by BS EN 13242. This ensures that the material is suitable for its intended use in pipe bedding and surrounding applications.
If the material is being used within highway construction within the UK, it must meet the specification laid out in the Series 500 Drainage and Service Ducts of the Specification for Highway Works.
Table 5/5: Grading and Geometrical Requirements for Filter Drain Material.
Sources:
Series 0500 – Drainage and Service Ducts (standardsforhighways.co.uk)