A basement or cellar can be such a useful part of your home. Maybe it’s a handy storage space, a cosy snug, a wine cellar (where’s our invite?) or even an extra room for the family. However, when you’re faced with peeling paint, mildew or that unmistakable musty smell, it can quickly feel like a less-than-welcoming space.
Damp basements are a common problem, particularly in older properties. Being below ground level means these rooms are naturally more exposed to moisture as they sit below the water level at the bottom of a property. Limited ventilation can make condensation an issue too.
So, what can you do about a damp basement or cellar? How do you paint damp walls in those rooms? We’re here to help you tackle damp cellar or basement walls, give you preparation tips before decorating and help you choose the best paint to use.
Why do basement walls get damp?
Cellars and basements sit below ground level, so their walls can be exposed to moisture in the surrounding soil. When groundwater builds up, water pressure can drive water through cracks, gaps or other weak spots in the brickwork, concrete and masonry.
Then there’s condensation to consider. Cellars and basements aren’t exactly known for having lots of windows. With less ventilation and colder surfaces, warm, moist air can condense on the walls.
There are several tell-tale signs of damp to look out for, including bubbling, flaking or peeling paint, a musty smell, mould or mildew growth, and even crumbling plaster. Eventually, a wet cellar wall can cause the plaster to blow. Persistent damp can also affect the building fabric, so it’s important not to treat the problem as purely a decorating issue. If you simply paint over a damp surface, it’ll hide it for a while, but the moisture is still there. And before long, that moisture will seep through your beautifully painted wall. Before choosing your paint, it’s important to work out what’s causing the damp and deal with it appropriately.
What type of paint is best for damp basement walls?
If your basement or cellar has damp walls, it’s important to choose your interior paint wisely, particularly in an older property where the walls may need to manage moisture naturally.
It’s not unusual for older properties with damp basements to have been treated with plastic-based, non-breathable plaster, render and paints in an effort to waterproof the room. Whilst that may keep the water out in the short term, you’re likely to see the issue return. Moisture becomes trapped under the paint surface and builds up. Ultimately, you’ll find that your damp basement walls become more and more saturated.
Instead of standard emulsion paints or other non-breathable paints (like damp proof paint), choose a cellar paint that helps trapped moisture to pass through your walls.
Our Claypaint is a highly breathable interior emulsion with a high clay content, giving it additional hygroscopic qualities. It’s ideal for painting basements, cellars and damp walls.
Claypaint isn’t a cure for damp, (no paint can be!), but being highly breathable means it can help the trapped moisture and water vapour escape from your walls rather than trapping it behind a less permeable coating.
It’s important to note that a breathable topcoat can’t make a non-breathable layer underneath it breathable. If your cellar walls have already been covered with waterproof paint, tanking or non-breathable plaster, you need to remedy that before applying another layer of paint.
Discover why and when to use breathable paint
How do I prepare a damp cellar wall for painting?
Start by doing some detective work to find out what’s causing your damp walls. Is the damp worse after heavy rain? Is there condensation on cold surfaces? Could you have a leaky pipe? Once you know what you’re dealing with, you can tackle the cause of your damp problem.
For more serious damp problems, particularly in older properties or where previous damp-proofing work has been carried out, it’s worth getting advice from an experienced specialist who understands how to treat damp basements and cellars. Basement conversions or properties with severe water ingress may also require professional tanking or waterproofing.
Once you’ve dealt with the underlying issue, before you start painting your basement or cellar wall, you need to make sure the surface is properly prepared.
- Remove loose paint and damaged plaster. You need a sound surface beneath a fresh coat of paint. It’s especially important to consider what’s already on the wall. Older layers of paint or other coatings could be trapping moisture. Look out for efflorescence (a powdery substance left when salts come through the wall). That needs to be removed before painting as well. You may need to use a primer, check the paint manufacturer’s guidance first.
- Treat any mould or mildew. Clean affected areas with a suitable product and let them dry completely. Painting straight over mould may hide it briefly, but it won’t deal with the conditions that allowed it to grow.
- Make suitable repairs. Repair cracks, leaks and damaged areas before decorating. Paint can make a wall look much fresher, but it can’t repair structural problems or stop water getting into your cellar. If you have lime plaster or an older solid wall property, choose repair materials that are compatible with it and allow the wall to breathe. A building specialist can advise if you’re unsure what’s already there.
- Remove excess moisture. Good ventilation can make a big difference in a cellar or basement. Where appropriate, improve the ventilation and airflow in your space or invest in a dehumidifier to help manage excess moisture. Remember though, a dehumidifer can help with humidity and condensation but it won’t solve water ingress through the structure of the building.
- Allow the wall to dry sufficiently before painting. Finally, give the walls time to dry before painting. A wall that’s visibly wet or crumbling needs more attention rather than another coat of paint. Always follow the paint manufacturer’s instructions for your surface, for Claypaint we advise that the moisture content of the surface needs to be less than 15% before painting.
Can painting a damp cellar help prevent mould growth?
You may have come across anti-mould paint or anti-damp paint when looking for a paint for your cellar. These products are formulated with particular properties intended to help resist mould growth or cope with damp-prone areas. But no paint can promise to keep mould away if your cellar remains damp, and the conditions that encourage it are still present. It’s vital that you tackle your damp problem and remove mould and mildew before applying paint.
A breathable paint can then help by allowing water vapour to move through your walls. Reducing trapped moisture can help create less favourable conditions for mould growth.
For older homes in particular, choosing a breathable paint can be part of a more sympathetic approach to managing moisture within the building.
Further advice on treating damp walls
Wondering how to spot signs of damp? Check our guide to the tell-tale signs of damp walls
Looking for a breathable paint for exterior walls? Your questions about Earthborn Silicate Masonry Paint answered
If you have a project that you need help with, contact us and we’d be happy to advise on whether Earthborn’s breathable paints are suitable for the job.
