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How to treat damp walls before painting

Person checking to see if their wall is damp before they paint it.

One of the most common and costly DIY mistakes you can make is painting over damp walls or ceilings. Inevitably, the paint bubbles and peels, putting you right back where you started.

The good news is that damp can often be treated, DIY-style, without having to call in the professionals. There are also a few very noticeable clues of developing damp that you can watch out for, and simple methods to try to stop it from making a reappearance.

In this guide, we’ll show you how to identify damp, fix the cause and treat your walls so that you can fully relax in your home knowing it’s sorted.

Table of contents

  1. What is damp in a house?
  2. Are there different types of damp?
  3. Condensation
  4. Rising damp
  5. Penetrating damp
  6. Other causes of damp
  7. How to check for damp on different surfaces
  8. How to treat damp walls
  9. Can you paint over damp?
  10. How to treat mould and damp on walls
  11. FAQs
  12. Protecting your home takes time, but it’s worth it

What is damp in a house?

Damp is a common problem in all types of home, whether you’re a homeowner, a landlord or a renter. Damp can make your home feel cold, unwelcoming and unhealthy. It’s also a cosy breeding ground for mould, which can be risky to your health.

Damp is essentially unwanted moisture that makes its way into structures over time. There are three main types of damp, which we’ll go into, along with how to spot each one and the best ways to fix it.

Is damp dangerous?

In short, yes. Damp, left unchecked, can be disastrous for your property (and finances) if you’re a homeowner or landlord, and it can also be hazardous to your health if you’re a homeowner or renter.

Water slowly erodes a building’s structure, rots timber and creates the perfect environment for potentially damaging mould to grow. If your property has any kind of mould problem caused by dampness, follow our in-depth guide for a number of different solutions on how to get rid of mould.

These are just some of the reasons why we strongly recommended that you don’t just simply paint over damp walls without fixing the problem first.

Are there different types of damp?

Yes, there are three main types of damp that you can find in your household:

You’ll need to know which you have in order to treat it properly, but it is important to keep in mind that it is possible for more than one type of damp to be present in your home.


A white PVC window and windowsill showing signs of condensation damp.

Condensation is a very common type of damp that can often invite mould into your bathroom or kitchen if you have poor ventilation. Condensation might also build up on exterior walls where it tends to be colder.

What are the signs of condensation?

You’ll be able to see beads of water on the wall’s surface and the dampness may be noticeable to the touch.

How to fix condensation

Condensation is the easiest damp problem to fix. It can often be solved cheaply and quickly, without the need for professional help.

Improving your home’s ventilation can help completely clear condensation. Effective measures include:

  1. Opening windows more frequently and letting your house breathe. If you have windows that lock partly open, this is a great idea.
  2. Get a dehumidifier and have it on for a few hours every day.
  3. Instead of quickly heating your home at a high temperature, put your boiler on at a lower setting for longer.
  4. In more extreme circumstances you could get a positive ventilation system.

Rising damp

A white wall that has been discoloured by water damage from rising damp.

Rising damp usually occurs in homes that are older – built in the early 20th century or even older. Damp simply rises up from the moist soil underneath the property and into the footings and foundations of the ground floor of houses.

More modern properties are built with damp-proof courses, which is a waterproof membrane that acts as a barrier between the soil and the house. Without a damp-proof course, older houses that are renovated with modern plaster, insulation, windows and doors, become very moist places indeed – the moisture gets trapped in the walls, et voila! You have a rising damp problem.

What are the signs of rising damp?

Rising damp creates visible stains, even tide marks on your walls. You can also get mould growing in corners.

How to fix rising damp

If you’ve got a significant rising damp problem, consider installing a modern damp-proof course. Whilst it might be expensive, it will help you prevent any further deterioration to the walls over time. It’s best to consult an expert if your problem is this severe.

If you’re lucky enough to have a milder case of rising damp, you can treat it in a similar way to condensation – ventilate, dehumidify, have your boiler on a lower setting for longer, and consider a positive ventilation system.

Penetrating damp

Water dripping through a white ceiling due to penetrating damp

Penetrating damp happens when water gets through your exterior walls and penetrates the inside walls. This may be caused by issues such as a leaking roof, due to broken or loose tiles, a broken or blocked gutter, damaged exterior walls, or even leaking pipes.

What are the signs of penetrating damp?

Penetrating damp often shows up suddenly as a damp patch on the inside of an exterior wall. It may also show higher up on a wall or even on your ceiling. There may be watermarks and some noticeable damage to your plaster.

How to fix penetrating damp

Find out the source of the problem – whether it’s your exterior wall, roof, gutter or pipes – and get it fixed as soon as you can to stop water from making its way into the walls.

Other causes of damp

Leaking pipes

A copper pipe suffering a slow leak at a join.

Pipework does have a lifespan and if yours is old or loose somewhere it can cause a leak. This may be a full-on gush or a slow trickle.

Damp from leaking pipes is similar to penetrating damp: it can show up suddenly as a visible damp patch on a ceiling, or underneath a fixture like a radiator or a sink. You might be able to solve any common water leaks at home by yourself, but more complex piping issues may need to be looked at by a plumber.

How to check for damp on different surfaces

You can often see or smell if you have damp most obviously in the winter, but there are less obvious warning signs you can look out for too:


Hold your hand against the wall. Does it feel cold or damp to touch? Flaking paint or curling wallpaper can be a dead giveaway. Mould shows up on painted and wallpapered walls and woodwork as black spots or grey growths.


Look for brown patches or stains on the ceiling – this is a telltale sign of a leak. Look for black speckles of mould.


Check your windows in the morning. Do they have condensation on them along with small puddles of water on the window sills? You can also get a build-up of black mould along the silicone sealant of the window frame.

Bathrooms and kitchens

Your grouting and sealant are the first port of call for mould. Thoroughly check inside cabinets and cupboards for stains, damp smells and mould.

Furniture and soft furnishings

Damp and mould love a tasty fabric. Check the inside of your curtains and blinds, and upturn your sofa to have a thorough inspection of the inside and the back of it.

Basements and unheated storage spaces

If you haven’t been down there in a while, prime your nostrils for getting a whiff of a musty smell. It’ll be fairly obvious if it’s an enclosed space. Also, check for stains and mould on walls and woodwork.

How to treat damp walls

A common error that homeowners make is to mistake a damp problem for a ventilation or condensation problem.

A damp problem is typically accompanied by condensation, as damp ramps up the level of moisture in the air. It’s not enough just to fix your ventilation if you have an unidentified damp problem; it’ll continue to wreak havoc on your property until you sort it out.

Can you paint over damp?

No. Never paint over damp. Damp is caused by a variety of structural failures, as detailed above, none of which can be fixed by painting over them. You must fix the underlying issue first.

Painting over damp materials allows the damp to continue to cause damage right underneath the lovely fresh layer of paint.

How to treat mould and damp on walls

Taking the time to fix a damp problem is essential not just for homeowners and landlords, but for anyone who is living in the property due to the effects it can have on your health if left untreated.

Here are 6 steps to treating mould and damp on walls so that you have a clean slate and a beautiful home.

1. Identify the cause of damp

Use our guide above to properly diagnose the type of damp you’re dealing with. Check walls, ceilings, pipes, gutters, basements, and under sofas – basically, leave no stone unturned.

2. Fix the source of the damp

Whether it’s a leak, a blocked gutter, or a sorely needed damp-proof course, once you’ve cut off the source of the damp, the rest of the steps will be easy.

3. Allow your walls to dry out

Once you’ve eliminated the source of the damp, your walls will need time to fully dry before you treat them. Ventilation is key – and a dehumidifier may be necessary.

You’ll soon start to see visible improvements like wet patches fading. Hallelujah! You may be left with peeling wallpaper, tide marks, stains or bubbling paint, but at least you can now tackle the aesthetics knowing you’ve fully fixed the damp.

4. Prep your walls

Once your surface is dry, repair any cracks and holes with wall putty, and sand it down until it’s smooth. Then paint it with a damp seal or a stain blocker paint so that any staining doesn’t penetrate through your next layers of emulsion.

5. Apply any waterproofing if needed

Perhaps you’ll want to add a waterproofing coat to your walls to avoid damp rearing its head again in the future, especially in kitchens and bathrooms. You can buy specialist primers for kitchens and bathrooms, that do exactly this.

6. Paint

Got damp-free, mould-free, dry and water-proofed walls? Now, you’re ready to paint. Phew!


How do I stop damp coming through walls?

You have to identify the source of the damp first – whether it’s condensation, rising damp, penetrating damp or a leaking pipe – so you know exactly how to fix it. This may mean simply ventilating your home better or you may need more drastic measures like fitting a damp-proof course to prevent rising damp.

Can you paint over damp walls?

No. Never paint over damp – it doesn’t address the root cause of bubbling paint or peeling wallpaper, and you’ll need to paint it again very soon. Fix the source of the damp then let the wall fully dry out before painting it.

Does opening windows reduce damp?

If your damp is mild and is caused by inadequate ventilation, then opening windows may completely solve your problem. However, damp patches can indicate a more serious issue that needs a bit more work, as simply opening a few windows won’t solve it.

Protecting your home takes time, but it’s worth it

Although damp can be time-consuming to fix and treat, it’s very doable using the steps above. Once you’ve really, truly eliminated the source of the damp, you probably won’t have to do it again, but if you’re a landlord with one or more properties to look after, you may want to consider our landlord cover if any leaking pipes or boiler problems occur, you can relax knowing we’ve got you covered. This makes it easier to manage any unexpected problems and expenses that may arise and help prevent mould from becoming an issue in the future.

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