Rising Damp Treatments
By Liz Ransome
Rising damp can be expensive to fix, so our guide will help you understand what the treatment options are before you call a professional in.
Rising damp is one of the trickiest types of damp to deal with and you'll probably need to get help from a professional.
Half of the people we surveyed who had experienced rising damp used a specialist damp company to deal with it, while 16% called in a builder and 3% used a surveyor. Just 12% dealt with it themselves.
One Which? member said: 'My advice would be to always get someone in if damp persists, as it may be possible to get it stopped without spending a fortune. If you ignore damp, it will only get worse and it may end up very expensive.'
As rising damp is less straight forward to deal with, it can be more costly. To get an idea of what the true costs are of dealing with rising and penetrating damp, see our guide to damp costs. It includes costs for different types of houses and room sizes, as well as a range of solutions.
Check your damp-proof course
To deal with rising damp, it's first worth checking whether you have a damp-proof course and damp-proof membrane, which stop water from the ground soaking into lower walls or floors (see image below).
Houses built before 1875 probably won't have one as this was when regulations came into force making them compulsory. You may be able to see whether you have a damp-proof course by looking for a thin strip in your wall near the bottom. You'll need to get an expert to confirm this and to try to ascertain whether you have a damp-proof membrane.
If you do have a damp-proofing course or membrane but are still experiencing damp, then they may have become damaged or worn over time. If these aren't working effectively, you may need new ones or have them repaired. Half of Which? members we surveyed with a rising damp problem got a new damp-proof course installed.
Repair or insert a damp-proof course
The most common remedy for a missing or damaged damp-proof course is for a builder or damp specialist to drill holes in your wall and inject damp-proof cream to act as a course.
But there are alternative solutions, such as cutting grooves into the brickwork and installing a piece of damp-proof course as opposed to a chemical one. This is more invasive than just drilling holes, so may be less easily hidden. Our damp costs page shows typical prices for both of these jobs.
Repair or add a damp-course membrane
If there is just a small patch of damp on your floor, you may be able to rectify the issue by painting over it to stop anymore coming through. You'll need to apply two coats of bitumen latex waterproof emulsion underneath the floor covering, which you can buy from many DIY stores. For extra protection you could lay reflective foil building paper (foil-side up) as well before it's totally dried.
If the damp is extensive, you may need to have the damp-proof membrane entirely replaced. This is likely to be costly, but may be necessary if the damp is widespread or other solutions haven't worked.
Dig away soil to level of damp-proof course
If you have a perfectly good damp-proof course, your damp problem could be caused by the ground level outside being built too near the top of the damp-proof course, which should be 15cm above ground level. The problem can be solved by digging away any soil on the exterior side of the damp wall to below the level of the damp-proof course. You could do this yourself, or you could get a professional to do it.
Tank walls and floors in damp-proof materials
Tanking a wall or floor is a building term that effectively means sealing it to protect it from moisture. This is usually done to areas that are already damp, and might be done by coating it (under the plaster for a wall or under the concrete for a floor) in asphalt (a thick liquid) or a membrane. The areas will have to be prepared first, and then decorated on top.
Tanking can be very expensive (our costs pages has details), so, like many other more costly damp work, it's worth getting a few opinions to help you decide whether it really is necessary.
If you're looking for a damp specialist, you can use our Which? Trusted Trader website to find recommended tradespeople who have been through our rigorous checks.
You can also recommend a trader yourself, and if they meet our high standards, you'll get a £40 John Lewis voucher.