Traditional manhole construction
100 mm
Traditional manholes feature a concrete base at least 100mm thick and walls constructed from brick, blockwork, or concrete appropriate to ground conditions
Traditional manholes feature a concrete base at least 100mm thick and walls constructed from brick, blockwork, or concrete appropriate to ground conditions. Wall thickness starts at 100mm for shallow, non-vehicular applications and increases to 200mm or more where ground pressure, groundwater, or traffic loads are present. Benching requires a smooth, steel-trowelled finish with rounded corners and a minimum fall of 1:12.
Basis in regulation
BS EN 752
Read the source
How to check it on site
Verify base thickness, wall material and thickness relative to depth and loading, and confirm benching is smooth, rounded, and has the correct fall.
Common failure
Inadequate wall thickness for site conditions, or poorly finished benching which promotes debris accumulation rather than smooth flow.
Last updated 23 August 2026. This is our editorial summary of publicly available regulation, not building control approval or a warranty determination.