When damp rears its ugly head, it can lead to all sorts of unwanted issues in the home. It’s not always easy to spot until obvious signs start appearing on walls and ceilings.
While painting over damp is a simple solution that can conceal marks and stains, it's not as simple as just applying a few coats of paint.
There is always an underlying cause of dampness, and this must be addressed first. Once the damp has been dealt with, you can then move on to painting over it. Here, we tell you how to prepare affected areas and select the right paint to achieve the best finish.
Painting over damp: what do I need to do first?
The appearance of damp means there is an underlying issue that is causing the problem and ideally this needs to be dealt with first before you start painting. Knowing how to stop condensation on walls and ceilings can be one quick way to solve a damp issue.
But there may be more serious issues such as rising damp, leaking pipes, broken down damp proof course and failing gutters.
Nicholas Donnithorne, UK Technical Manager at Rentokil Property Care says, “the first thing you need to do is identify and fix the cause. Is it coming from inside the building, seeping through the walls, creeping up from the ground, from natural water or from a leaking pipe or drain?
"If you do not identify and remediate the source, whatever you do to treat or hide the damp will fail in the long term," he warns.
One of the causes, rising damp, "is caused by moisture travelling up through the brickwork or masonry," adds Nicholas. "It’s the bane of older buildings, where the damp proof course (DPC) may have deteriorated – or be missing altogether.”
Another common issue found in older buildings is salt damp. “This is caused by hygroscopic salts trapped in the wall as a result of groundwater rising up it," he explains. "These salts suck moisture into the plaster surface, meaning the damp patch will come and go with the weather.”
Nicholas warns, “if you see the telltale signs of a damp problem, the worst thing you can do is to ignore it. Left unaddressed, damp can grow into a bigger, more costly structural issue.”
Nicholas Donnithorne is the UK Technical Manager at leading property care firm Rentokil Property Care. He has over 45 years’ experience in the property sector, having started out in its research laboratories, and is a recognised expert on damp, mould, and other common property issues.
Try these tools and paint for painting over damp
An oil-based white undercoat paint that will help keep damp and mould at bay. Apply with a roller or paint brush and leave to dry. Touch dry in 4 hours.
This budget-friendly paint set includes a 4-inch roller and tray, along with two foam roller sleeves, ideal for a lint-free finish with gloss, eggshell, and satin paints.
A good-quality self-priming matt paint that is mould- and mildew-resistant and recoatable within 2 hours. Washable and scrub-resistant.
What paint should I use on damp?
Before you start painting over damp. Nicholas Donnithorne offers the following advice.
"Damp proof paints and concealant sealers may initially cover up the problem, but if the source of the damp isn’t remedied, sooner or later the paint film will be breached." "Worse still, as many damp proof paints seal water in, they may even make matters worse," he warns, so it's always best to proceed with caution.
If you are dealing with ugly stains and marks left on previously painted interior walls and ceilings, you want to start with a paint that will cover the stain and block it from reappearing. Zinsser B-I-N from Amazon is a good all-round primer/sealer/stain killer that can be used on interior and exterior surfaces. An alternative option is to use an oil-based paint like Dulux Trade Undercoat.
If painting a high moisture area like a kitchen or bathroom, a mould resistant paint like this Zinsser Perma White Self-Priming Interior Paint from Amazon is a good choice for the top coat and to keep surfaces looking good for longer.
For exterior surfaces use a suitable masonry paint such as this Sandtex masonry paint from Amazon. This is suitable for render, concrete, blocks and brick and is available in smooth and textured finishes. Alternatively, try this Dulux Weathershield masonry paint from Amazon. Or for more extreme conditions try this Sandtex Trade X-treme X-posure Smooth Masonry Paint.
Three steps to painting over damp
Make sure you have the right paint, clean brushes and rollers and dust sheets – like these brackit 8-Pack, Large Plastic Dust Sheets for Decorating from Amazon – on hand before you start.
1. Prep and clean area
Peeling paint and loose plaster will need to be removed before you start painting. Get a scraper to remove loose debris and finish with a wire brush. Wash down the walls with a suitable mould killer like this Zinsser Professional Mould Killer and Remover from Amazon.
2. Fill and sand
Damp will cause holes and cracks in walls and ceilings and these need to be filled before you paint. Use a suitable all purpose filler or patching plaster like this Palace Langlow Patching Plaster from Amazon for larger cracks that need fixing.
Leave to dry as per the manufacturer’s instructions and then rub down with a 120-180 grit sandpaper grade. Then add a primer coat to help seal the plaster and leave to dry.
3. Apply top coat
Start by applying a layer of mould resistant paint. This is optional, alternatively you can just apply a layer of oil based paint. To finish, add your preferred top coat.
FAQs
How long does it take to dry out a damp wall?
In short, this will depend on the type of wall you have, the severity of the problem, and the conditions.
Jess Thomas, Damp expert and MD of Drainage Central says, "a damp wall can take a few days to a few months to dry out after the source of moisture is addressed, with the overall time depending on the cause of the damp, the extent of any damage and the type of wall."
Nicholas Donnithorne agrees and offers the following broad guidelines. "For every 25mm of wall thickness, the wall will take about a month to dry if there is bare brickwork on one side. If the outside is rendered and the inside plastered, the drying out process will take much longer."
So how can you speed up the process? Natural ventilation, i.e, opening the windows, will help air flow through a room, which encourages moisture to evaporate quicker. And pumping up the heating in a home will help as well.
Alternatively, the best dehumidifiers will help suck moisture out of the air which will shorten drying times. If dealing with rising damp, removing skirting boards will expose the bottom of the wall to air, which will again help remove moisture much quicker.
Jess Thomas is the Managing Director of Drainage Central and an expert in the drainage and plumbing industry. Jess continually provides valuable insights on a wide range of industry topics, including damp, and is dedicated to helping homeowners find effective solutions to their drainage problems.
What happens if you just paint over damp?
Painting over damp is a short-term fix; it may hide the problem for a few weeks or months, but in the long term, you will be causing more issues. The damp will still exist, and adding more paint can help keep the damp in the wall or ceiling, making the problem worse rather than better.
Jess Thomas says, "painting over damp without fixing the cause will trap moisture, which will affect the adhesion of the paint and only be a temporary solution. The damp problem can potentially worsen, which can result in structural damage or mould growth.
"Paint cannot adhere to a damp surface properly, so it will bubble and peel after it has dried," warns Jess. "The dry paint will also trap moisture in the wall or ceiling, making the damp worse and stopping it from being able to dry out."
Can I use a dark colour paint to hide damp?
You can use any colour paint you want to hide damp, as long as the area has been prepared properly and the right steps taken. However, adding a dark colour - especially over white - will help hide any stains quickly. If stains do start to reappear they are typically harder to spot on a darker colour.
Damp can lead to mould and you might want to try to remove mould from walls without damaging paint, before you go further. It can also affect wood, so check out how to clean mould off wood to ensure you get a clean surface for painting.
