Damp Proofing Clapham

Clapham grew up around Clapham Common, and most of its housing went up between the late Georgian period and the early 1900s. The Old Town and the Common's North Side keep some of the oldest houses, while the streets around Clapham North, Clapham Manor, Abbeville Village and Clapham Park are lined with Victorian and Edwardian terraces, many of them now split into flats.

The Common sits on river terrace gravel over London Clay. The gravel drains well at the surface, but water moves through it and collects where it meets the clay below. That is why many Clapham cellars and lower ground floors stay dry for most of the year and then take in water after a long wet spell, often in late winter when the ground is fully saturated.

Clapham has a lot of cellars and an even larger number of basement conversions. Turning a cellar into a bedroom or kitchen changes what the walls and floor have to do. A space that was fine for storage usually needs a cavity drain membrane with a sump and pump, or a tanking system, before it can be lived in, and we design these to BS 8102:2022.

Above ground, the typical Clapham terrace has solid brick walls, suspended timber floors and a slate damp proof course that may be well over a century old. Common faults include damp proof courses bridged by raised paths or front garden paving, air bricks blocked by later work, and rising damp in front walls and party walls.

Bay windows, stucco details and rendered lower walls are everywhere, and once they crack they let water into the wall behind. Cement render and gypsum plaster added in past refurbishments often hold moisture against the brick, so what looks like rising damp is sometimes penetrating damp or simply trapped moisture.

Damp left in a floor void can lead to wet rot in joists and, in the worst cases, dry rot spreading into skirtings and floorboards. We check floor voids and sub floor ventilation as part of every survey, so timber problems are found before they become structural.

Clapham also has a high share of rented and converted flats. Smaller rooms, more occupants, laundry dried indoors and missing or undersized extract fans lead to condensation and mould, particularly in bathrooms, kitchens and bedrooms with north facing walls.

Chimney breasts are another frequent source of trouble in Clapham terraces. Once fireplaces are blocked up and stacks are capped badly or left uncapped, rain and condensation inside the flue leave damp patches on chimney breasts, often carrying salts that stain new plaster. Party walls shared with a neighbour can also carry damp across, so we look at both sides of the problem before recommending work.

Each of these problems needs a different fix, so the survey comes first. Our CSSW and CSRT trained surveyors take moisture readings, use thermal imaging where it helps, and check drainage, pointing, ground levels and ventilation before recommending anything. You get a written report with photos that explains the cause in plain language and sets out the fix, with no obligation.

We cover all of SW4 and the neighbouring parts of SW8, SW9 and SW12, from the Old Town and the Common to Clapham North, Clapham South and Clapham Park. Surveys are arranged from our London office at 45 Fitzroy Street.