Is a damp cellar a problem? What to look out for when buying

For many buyers, having a cellar or basement is an attractive feature: extra storage, a potential conversion or simply a useful additional space. But the same underground position that makes a cellar appealing also makes it vulnerable to moisture, rot and structural issues that a survey will need to assess carefully.

More information in our guide to damp in property surveys.

The main issue with cellars is damp. A damp problem left unaddressed can cause significant long-term damage to a property and its structure.

If the cellar has not been converted into a living space, moisture will often seep through the foundations from the surrounding soil, or rise through the floor if it is little more than a bare earth base. Rising damp from below the floor slab can be a contributing factor too, particularly in older properties without an adequate damp-proof course.

Left unmanaged, dampness creates the conditions for mould and mildew to grow, which can spread to other parts of the home and affect the health of those living there, particularly anyone with respiratory conditions.

Damp also creates ideal conditions for wooden structures in the cellar to begin rotting. This includes the joists and floorboards of the rooms above, which then creates instability in those above-ground spaces. There is also the likelihood of unpleasant odours spreading through the rest of the house.

There are practical steps that can reduce damp in a cellar. Ensuring adequate airflow is the starting point: airbricks in the external walls should be clear of debris, any connections to chimneys or flues should allow air to flow freely, and blocked fireplaces should have a suitable grille installed to maintain airflow.

A more comprehensive solution is to bring in a specialist company to carry out cellar damp proofing, lining the walls with a waterproofing layer that blocks moisture from entering. One established method is cellar tanking, which involves applying a waterproof coating directly to the masonry surfaces. For persistent or severe damp, a specialist damp treatment may also be recommended before any lining work begins.

It is worth noting that you cannot reasonably request a seller to waterproof a cellar to make it a living space as part of a purchase negotiation. What you can do is use the survey findings to negotiate on price to reflect the cost of any remedial work required.

Before the survey, inspect the cellar yourself if it is safe to do so. If you detect the smell of damp or mould, or can see evidence of moisture, staining or deteriorating timber, make a note of it. If the current owners use the cellar, look at what is stored there and whether furniture or belongings show signs of damp damage.

A list of specific concerns to raise with your surveyor is always useful, as they can focus particular attention on the items you are worried about.

If you are buying a property with a cellar or basement, a RICS Level 3 building survey is strongly recommended. The surveyor will use a range of tools to assess the property, including measuring moisture levels in areas like the cellar, bathroom and downstairs rooms. Where readings are high enough to warrant concern, they will inspect the cellar in more detail, looking for evidence of damp-related damage.

If the cellar has been converted, the surveyor will assess the materials and techniques used to damp-proof it and identify any potential issues with the workmanship or materials.

The findings will be presented in the report using a traffic light rating system: green for no problems identified, amber for issues that do not require immediate action but will need attention in the future, and red for significant or urgent problems requiring immediate remedial work.

Where problems are identified, the surveyor will also advise on the type of remedy required and give a broad indication of the likely costs. This gives you a clear basis for deciding whether to proceed with the purchase, renegotiate the asking price or walk away.

A RICS Level 2 HomeBuyer Report will note visible damp concerns but will not go into the same depth. For a property with a cellar, the additional detail from a Level 3 is usually worth the cost. You can find out more about what each survey level costs on our survey cost page.

At Surveyor Local, we work exclusively with RICS-accredited chartered surveyors across England and Wales. Our team can arrange a survey quickly and at a competitive price.

Call our friendly team on or get a survey quote online.