How to Waterproof a Basement – A Comprehensive Guide

Many London homes have a basement, as this was popular from the Victorian times right up until the present; land is expensive in our capital city and adding below-ground living space is a very attractive proposition. You can’t build up or sideways, but with planning permission, a basement is an effective way to add living space to a home.
In this short article, we present the most common ways to waterproof cellars and basements.

Basement Tanking in London

As you would expect, basement waterproofing is a busy industry in London; sitting on a bed of clay, there are many wet regions where buildings require basement tanking. When a homeowner books a survey, we carry out a thorough damp inspection throughout the building, with special attention on the basement.

The common method involves removing all plaster from the walls and ceilings, then cleaning the substrate. A thick layer of waterproof render is applied and when this is completely dry, a second layer is applied, which forms a watertight seal; a skim of plaster and the walls are complete. The ceiling would be special water proof membrane with several coats of waterproof plaster and the floor might require channels dug out and a special membrane installed, which should keep the interior dry.

Cavity Drainage System

This is the best solution for a basement in ground with high moisture content; basically, the ceiling, walls and floors are fitted with a special studded membrane to create a cavity, which holds any water and there are grooves in the floor to send water to a sump, where it is pumped to drainage points. This is a major project that might take up to a week to finish; everything would be removed and all debris taken out before the damp-proofing work can start. Once the work has been completed, regular inspections should be done to ensure there are no leaks.

Ventilation

Every basement requires a positive rate of airflow, which can be achieved with extractor fans at both ends of the basement. This is essential in order to keep the air dry and if you install some form of heating, this will help keep moist at bay. A large underground space would require a ducting network for both heating and ventilation and a sump pump might be required.

New Builds

If a basement is under construction, it is much easier to waterproof, as the membrane can be fitted during the building process. If you are still in the planning stage of the build, having the ground surveyed will help you choose the best tanking method and you can liaise with the builder.

Damp-Proofing Contractors in London

While we do not carry out damp-proofing work, we do have a close working relationship with the best damp-proofing contractor in London and they offer a solid 30-year warranty on all of their work. We have been surveying London homes for many years and if you would like an accurate evaluation by a certified professional of your London home, call London Damp Specialists on 020 7205 4886 or complete the online booking form and one of our damp surveyors will arrange to inspect the property.