Understanding Damp: What Homeowners Need to Know

12 January 2026

One of the most common questions we get during a building survey is about damp. It’s a worry for many property owners, and for good reason – damp can affect both comfort and the long-term condition of a building.

Broadly speaking, there are two main types of damp: penetrating damp and rising damp. Some surveyors also include condensation in the conversation, though technically this isn’t damp in the same way, as it’s caused internally rather than coming from outside the building.

Penetrating damp happens when water enters a building through a defect in its structure. Think of a leaking gutter or a faulty flashing – rainwater gets past the external surface and into walls or ceilings. During a building survey, our team investigates these issues fully, checking for the source and the extent of any damage.

Rising damp is a little trickier. It’s moisture that moves up a wall, usually from the ground, often working alongside penetrating damp. Commonly seen where external walls are in contact with soil, or in basements with high water tables, rising damp carries moisture through plasterwork. It can leave telltale “tide marks” or staining on internal walls. Typically, this moisture travels up to around 1 metre from the ground level.

Rising damp always involves some penetration from the outside, but tests – including salt analysis – can help differentiate groundwater rising through the walls from rainwater intrusion. This is part of the detailed defect diagnosis we carry out during building surveys.

Understanding the type of damp is just the first step. Correct diagnosis is essential before deciding on any repairs or treatment. Our surveyors are here to help with both building surveys and targeted defect investigations, ensuring you know what’s happening with your property and what action may be needed.