The subject of damp in buildings invites much comment and speculation. The issue is often misunderstood and proposed solutions are often expensive, damaging, and usually affect the continued performance of your property. Traditionally constructed buildings, (normally those built before 1919) can be prone to damp problems if not properly maintained. Frequently this can also be attributed to later changes and modifications. Understanding how a building is constructed is key to dealing with various forms of decay resulting from excessive moisture levels, or “damp”, as it is commonly referred to. Unlike modern construction methods which rely on impervious barriers to protect against moisture, a traditionally built structure needs to breathe to accommodate moisture. It relies on the free, unrestricted movement and dispersal of moisture through its materials to perform effectively. The presence of surface staining, mould and/or stale air, usually indicates that a problem has interrupted this process and the cause requires attention. By describing the common causes of damp, and identifying the simple points to look for, this INFORM seeks to illustrate the best approach to help remedy the problems.