Part of Ward Property Services UK LtdBelow-ground structures are permanently in contact with wet ground, so basement waterproofing is about managing water rather than hoping to exclude it. The relevant guidance, BS 8102, sets out three types of protection: barrier systems, drained cavity systems and integral structural protection. The right choice depends on the construction, the water table and how the room will be used.
For most Surrey basement conversions we specify a cavity drain membrane system with perimeter drainage channels and, where gravity discharge is unavailable, a sump and pump with battery backup. This approach accepts water at the structure and controls it, rather than relying on a coating to resist hydrostatic pressure indefinitely.
Common signs
- ✓ Standing water or persistent damp patches on basement walls
- ✓ Efflorescent salt deposits on brickwork below ground
- ✓ Musty smell and high humidity in a lower ground floor
- ✓ Damp appearing after heavy or prolonged rainfall
- ✓ Rusting fixings and decaying skirting at floor level
Likely causes
- • Hydrostatic pressure from a high or seasonal water table
- • Failed or absent original tanking
- • Defective external drainage and surface water discharge
- • Porous masonry and lime mortar in Victorian sub-structures
- • Condensation from warm air meeting cold below-ground surfaces