The Very Real Threat of Damp & Mould to London Homes

The Very Real Threat of Damp & Mould to London Homes

3rd July, 2025

London sits on a clay layer that is part of the Thames Valley Basin, which means that wet ground is a common issue in London homes. This is one of the reasons why damp and mould can impact buildings, especially older properties and in this blog, we take an in-depth look at damp and mould and how it can damage London homes.

Ground-based moisture (rising damp)

Known as rising damp, wet ground causes moisture to creep up the exterior walls, damaging building materials such as masonry, brickwork, mortar and timber. Because of this, all structures should have a damp proof course, a layer of thick bitumen strip that is sandwiched between the first few courses of bricks and that prevents moisture from crossing that barrier. Over a long period of time, this DPC membrane can be damaged; ground subsidence, for example, can lead to the DPC being torn, thus breaking the barrier and allowing dampness to rise up exterior walls. If you are not paying attention, you might miss the tell-tale signs of rising damp and by the time you realise, a lot of damage has occurred to masonry, mortar and timber. Moisture can climb walls using capillary action, much like paper soaks up water and over time, damp can reach the window frames.

Penetrating damp

Moisture that enters a building via the roof or exterior walls is known as penetrating damp because it penetrates all building materials. It might be a few missing roof tiles that enable rainwater to enter the internal roof structure, or blocked guttering that forces rainwater to run down the outside of exterior walls; a north-facing wall might have to endure years of driving rain and eventually, the wall is penetrated by the constant damp. Regular building inspections are advised, which would give you a heads-up and you can carry out much-needed repairs. The longer damp is allowed to penetrate a building, the more damage it will cause.

Condensation

Caused by excess moisture in the air, droplets of water can form on cold surfaces if the conditions allow it. Certain habits, such as drying clothes indoors or leaving the bathroom door open when running a hot bath, promote condensation and should be avoided. Do open the windows when cooking or running a hot bath, as this helps to remove excess moisture from the space. At London Damp Surveys, we use hygrometers and moisture meters to accurately measure moisture content to help pinpoint the underlying cause of condensation.

Professional damp surveys

We are proud of our comprehensive damp inspections for London homeowners; our fully certified damp surveyors use cutting-edge equipment to accurately determine the presence of damp, mould, condensation and timber rot. If you are interested in buying a London property or you wish to find out if your home is suffering from damp, call us on 0207 305 5997 or fill in the form on this website and we will arrange to survey your home and get the results to you within 24 hours.