Waterproofing a Basement – The Homeowner’s Guide

Waterproofing a Basement – The Homeowner’s Guide

3rd July, 2025

Many London homes have underground living space; some are wine cellars, some offices and some are rented out as flats, whatever you use it for, a basement needs to be waterproof, especially if your home happens to be on one of the huge clay beds in the Thames Valley Basin.

In this article, we outline the two most popular methods to waterproof a basement.

Basement Tanking

This is a term used when the walls are coated with a waterproof render such as Sika, the empty basement would be prepared and several layers would be applied, also on the ceilings and floors to create a watertight space. Adequate ventilation is required and regular checking of humidity levels. This is the preferred solution to mild damp issues and there is top-rated basement tanking in London from specialists that offer a 30-year guarantee on all their work. If you think damp could be present in your basement, contact London Damp Surveys and if there are damp issues, we will find them.

Type C Cavity Drainage Systems

Generally, the most popular, installing a cavity membrane with channels to a sump area where water can be pumped to designated drainage points. Studded membrane is fitted to the floor, walls and ceiling, allowing water to drain away without damaging the structure. This is definitely specialised work, so you should use an accredited damp-proofing company, one that offers long-term warranties on their work. Installing a drainage system is usually the first priority, then surfaces are prepared for the studded membrane and all seals are in place. There is a sump area and a small pump to direct the water to the main drains, making it ideal for areas where water collects; if you would like your basement inspected for damp and mould, we at London Damp Surveys can send one of our certified surveyors to your home. Consult with the experts to get it right the first time; we have a working relationship with the best damp-proofing outfit in London and they guarantee their work for 30 years, which brings peace of mind.

Avoid Costly Repairs

If damp is not treated, it can quickly lead to very costly repairs, you might have to vacate the property until the damp-proofing work is completed. In the event you are planning to buy a property with a basement, we recommend having the property surveyed for damp, mould, condensation and timber rot. It is easy to conceal damp issues with a few coats of paint and waterproof plaster and when we survey a building, you receive a detailed report on every aspect of the property. Our pre-purchase damp survey is designed to identify any damp, mould or condensation; you receive a detailed report within one day of the survey being completed.

Don’t delay, call London Damp Surveys on 0207 305 5997 and have your basement inspected by a qualified damp surveyor.