Major Causes of Damp & Mould in London Homes

Major Causes of Damp & Mould in London Homes

3rd July, 2025

London and surrounding areas are in the Thames Valley Basin, which means there is a lot of moisture in the ground and in this short article, we take an in-depth look at the common causes of damp and mould in London properties.

Rising Damp

Every building in the UK should have a damp proof course installed between the lower courses of brickwork; in older homes, this would be a bitumen-based strip that prevents moisture rising up the walls. The damp proof course can easily become damaged by ground movement or just old age and should this membrane split or tear, moisture will rise up the walls using a capillary action. It is often the case where an old damp proof course cannot be replaced and in such a situation, we would likely recommend injecting a chemical DPC into the brickwork.

Leaking Roof

A leaking roof allows water to enter the internal roof structure and should the leak go undetected, this could lead to serious damage to joists and rafters. Strong winds can lift clay roof tiles, so it is crucial that you have your roof inspected on a regular basis. Blocked guttering leads to excess rainwater running down the exterior walls, which could result in penetrating damp. Your roof is not entirely visible from the ground, which is why you should contact London Damp Surveys to carry out a thorough damp inspection that includes a roof inspection.

Exterior Wall Damage

Driving rain can erode masonry, brickwork and mortar and when this happens, moisture can enter the building and cause a lot of damage. Regular inspections would reveal tell-tale signs like moss growth and crumbling mortar; you can poke the material with a screwdriver to test the integrity of the substrate. A compromised outside wall can be a major problem, especially if you are not aware and it will eventually lead to damp attacking the interior walls. Masonry, brickwork and render are all under threat from penetrating damp, so regular inspections are advised.

Pre-Purchase Damp Survey

If you are planning to make an offer on a London property, we advise you to book our pre-purchase survey, which is designed to accurately determine the condition of the property with regards to damp, mould and timber rot. Our damp surveyors use cutting-edge technology to inspect a property, such as thermal imagery, moisture meters, hygrometers, endoscopic cameras and drone imagery. It is very easy to conceal damp issues with some paint and plaster; it is best to have the house professionally inspected by a qualified damp surveyor. You will receive a detailed written report, usually within 24 hours of survey completion and you can rest assured that our survey is thorough and covers every aspect of damp, mould and timber rot.

Don’t wait to find out whether or not your home has damp or mould issues, call London Damp Surveys on 0207 305 5997 anytime or simply fill in the online form on this website and let the professionals accurately appraise your London home.