Cambridge has thousands of Victorian and Edwardian properties with cellars that were built for coal storage, not habitation. Many of these spaces are damp, dark, and underused — but with the right waterproofing approach, they can become genuinely useful rooms.
Cambridge has thousands of Victorian and Edwardian properties with cellars that were built for coal storage, not habitation. Many of these spaces are damp, dark, and underused — but with the right waterproofing approach, they can become genuinely useful rooms. Cellar tanking is one of the most cost-effective ways to add usable space to a Cambridge home.
Cellar tanking refers to the application of a waterproof cementitious coating — a tanking slurry — to the internal walls and floor of a cellar. The coating bonds to the masonry and forms a continuous waterproof barrier that prevents water ingress from the surrounding ground. It's a Type A waterproofing system in the BS 8102 classification.
Tanking is most effective in cellars where the water pressure is relatively low — where the water table is not persistently above the cellar floor level, and where the walls and floor are structurally sound with no significant cracking. In these conditions, a properly applied tanking system will keep the cellar dry and can be finished with a sand-cement render and decorated.
If the cellar is subject to significant hydrostatic pressure — for example, if it floods during wet winters or if the water table is consistently above floor level — tanking alone is unlikely to hold long-term. Water under pressure will find any weakness in the coating, particularly at wall-floor junctions and around pipe penetrations. In these situations, a cavity drain membrane system (Type C) is more appropriate, or a combined Type A + Type C approach.
The most common reason tanking fails is inadequate surface preparation. The masonry must be clean, sound, and free of loose material, old paint, and efflorescence before the tanking coat is applied. Cracks must be cut out and filled with a hydraulic repair mortar. Wall-floor junctions must be formed into a coved fillet to prevent the coating from bridging a sharp internal angle. Skipping any of these steps will result in delamination and failure.
A properly specified cellar tanking job includes: a pre-work survey to assess water pressure and structural condition; preparation of all surfaces including crack repairs and coving; application of a minimum two-coat tanking slurry system to walls and floor; a sand-cement render coat to provide a finish surface; and a written guarantee. The work should be carried out by a specialist contractor, not a general builder, and the guarantee should be backed by the contractor's professional indemnity insurance.
Cambridge sits on heavy clay soils with a high water table in many areas. Combine that with a large stock of Victorian and Edwardian terraces, and damp becomes one of the most common property problems in the city.
ReadRising damp is one of the most misdiagnosed conditions in the building industry. Knowing the genuine signs — and how to distinguish them from condensation or penetrating damp — can save you from unnecessary and expensive remediation work.
ReadBS 8102:2022 defines three types of basement waterproofing system. Understanding the difference between them — and when each is appropriate — is essential before committing to any basement conversion or cellar renovation in Cambridge.
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