One of the most common and costly DIY mistakes is trying to paint over walls or ceilings suffering from damp and mould. Before long, the paint is bubbly, peeling and mouldy again – your money wasted and your property damaged even more.
Whether damp proof paint will be effective depends on what you’re trying to treat and what is causing your damp. We use damp proof paints at Environ, but only as part of wider damp proofing work. By itself, it is a temporary fix at best.
But before I explain why painting over damp walls is hardly ever a long term solution, first let’s go over the different types of damp proof paint and what they treat.
Anti-condensation, anti-mould and anti-damp paint
- Anti-condensation paint contains insulating materials which improve the thermal performance of surfaces it’s applied to. It can reduce wetness on walls and associated mould if condensation was caused by a cold surface.
- Anti-mould paint contains fungicides which kill mould spores and prevent their spread. These fungicides lose effectiveness over time, so they are always a temporary solution, but the best can last for 5+ years. Anti-mould paints do nothing to reduce damp.
- Waterproof paints create a seal which stops damp from entering the interior. However, moisture can build up behind the paint and continue to cause damage. It can also stop brick walls from “breathing”, making damp issues even worse.
Do You Have Damp, Condensation or Both?
Damp is unwanted moisture entering a structure and it comes in many forms, from penetrating damp seeping through walls to rising damp coming up from wet soil.
Unchecked damp is disastrous for a property, as the water erodes building materials, rots timbers and creates an environment for mould to grow. Damage caused by damp can reach hundreds of thousands of pounds.
While they can both cause wet surfaces and mould growth, damp and condensation have very different causes – but can and often do happen at the same time.
Condensation occurs when moisture in the air comes into contact with a cold surface and condenses. Occasional condensation isn’t a problem, but if a surface is continuously wet it can lead to growth of mould and damage to building materials.
If you have a condensation problem, it either means there is too much moisture in your air or your surfaces are too cold.
This is why damp and condensation often occur simultaneously, as damp increases the level of moisture in the air. People often treat their condensation while failing to diagnose their damp problem, which continues to eat away at their property.
Anti-condensation paint won’t reduce moisture in the air, but it can improve the thermal performance of your walls so that they are less cold and thus less at risk of damp. It can work, but only if cold surfaces are the sole cause of your condensation.
If the mould on your walls is coming from damp rather than condensation, anti-condensation will do nothing at all to fix your problem and will only provide a fresh coat of paint.
Never just paint over a damp problem
In all my years doing damp surveys, I can count on one hand the number of damp problems which could be solved entirely with damp proof paint.
Most of the time, condensation is caused by poor ventilation, which is better treated with the installation of a PIV unit or other ventilation systems.
PIV (positive input ventilation) units create positive air pressure in the house to push out old, stale, damp air and bring in fresh, clean air. The running cost is just pennies a day, and will dramatically reduce condensation while also improving air quality.
Damp, on the other hand, is caused by a variety of structural failures, none of which can be fixed by painting over them. There’s too much to cover here, so if you want to learn more about the different types of damp and their causes, read our articles about rising damp and penetrating damp.
If you’re completely certain that anti-condensation, anti-mould or waterproof paint is the right solution for your damp problem, make sure that you completely strip back any materials affected by damp or mould first.
Painting over damp materials will allow the damp to continue to cause damage beneath your fresh layer of paint, while wiping off mould and painting over it will leave mould-infested materials beneath. Before long, the mould will return.