The DIY Fix is reader supported. When you buy after clicking a link on our site, we may earn an affiliate commission.
Damp proof paint is a deceptively simple cure to problems with damp or mould. This has a lot of people wondering how does damp-proof paint work, or if it even works at all. There is a lot of misinformation out there. However, it can work when you approach damp proof paint properly. It does a great job of treating some damp problems on external and internal walls. So how exactly does it do that?
Damp proof paint contains a water-reactive agent. Once applied to a surface, this stops moisture from soaking through into the wall. It forms a damp proof, protective barrier that will not allow water in, but still lets moisture evaporate and the wall breathe.
Doing this effectively is different depending on the wall’s material and how you’ve applied the paint. That’s why it’s important to do your research before you use damp proof paint. You need to know if it actually works for your type of damp.
Different Damp Paints and How They Work
Damp proof paint is a more general term you’ll often see on paint, but there are a few different types. Each can treat a different type of wall and contains a different water-reactive material. These are the main types and how they work:
Internal Damp Proof Paint
Internal damp proof paint is formulated to stand up to the moisture that will hit a wall from the inside. It is one of the simplest ways to damp proof internal walls. This damp proof paint will typically form an interior seal. This allows the walls to breathe and let out trapped moisture by evaporating. However, it stops the moisture built up on the wall from actually soaking in and becoming damp.
External Damp Proof Paint
External walls can be a bit trickier to damp proof, especially only using paint. They can be made from a lot of different materials, and hit by rain and snow. External damp proof paints have to stand up to this and dramatically different temperatures.
External damp proof paints are made from different materials depending on what they’re waterproofing. Masonry paint is applied to last a long time and work on brick. Whereas paint that works for wood or interiors needs to be more breathable. Get the right paint for the right surface, or it won’t be able to form a breathable seal. You should also make sure the surface you’re applying it to is clean. Debris or cracks can cause a hole in that damp proof seal that renders it less useful.
Does Damp Proof Paint Actually Work?
Despite what you might have seen, damp proof paint does actually work. However, it works in specific situations and when applied properly.
Damp proof paint will not work as a cheap ‘fix-all’ solution for every damp problem. It works great for treating damp that occurs from condensation but not from structural flaws. In these situations, damp proof paint can be applied to a wall once the damp has been removed. It will act as a waterproof layer, stopping moisture that forms on the walls from soaking in again. If applied properly, it will also allow moisture to evaporate. It is often most effective when used in tandem with damp proofing courses inside of the wall.
What is important for making sure that it actually works is to approach the problem from the right angle. Figure out what type of damp you have, and make sure that damp proof paint can actually fix that problem. Then, make sure you’re applying the right damp proof paint for the material and conditions of your wall.
When is Damp Proof Paint Not the Solution?
There are some situations when internal damp proof paint is not going to work. Internal paints do work, but they will not if the damp is being caused by a more serious issue, such as penetrating damp or rising damp. While helpful for preventing mould forming via condensation, these types of damp aren’t going to be stopped by paint.
On external walls, there are a few more caveats for damp proof paint working. The paint isn’t going to be able to make a proper seal over walls with a lot of holes or cracks. Equally, if you use paint designed for brick on a different surface then the paint will not allow water to evaporate out as well as it should. This will eventually cause your paint to fail.
Damp proof paint does work. However, you need to make sure you’re using it in the right situations.
Examples of Popular Internal Damp Proof Paints
Not all damp proof paints are created equal. Since a lot of people use it as a quick fix for any damp problem, there is a lot of paint out there that does little more than provide a quick fix. Essentially, some are just normal paint to cover up damp rather than waterproof the wall. These are some of the better options on the market, those that seem to actually work for most people:
- Thompson One Coat Damp Seal – This is for interior walls and acts as a primer that is a waterproof seal and the wall to breathe. It is relatively low cost and most customers are happy with the results. To learn more about Thompsons One Coat Damp Seal Click Here
- Ronseal One Coat Damp Seal – This can be used on walls, ceilings, and even applied to damp surfaces. This is a good choice if you have a lot of surfaces to treat. To learn more about Ronseal One Coat Damp Seal Click Here
- Johnstone’s Damp Proof Paint – This treats your wall and dries fast. While you can add a layer of matt or emulsion on top, this paint won’t look as bad without it. To learn more about Johnstone’s Damp Proof Paint Click Here
To read our full guide for internal damp proof paints Click Here.
Examples of Popular External Damp Proof Paints
Exterior damp proof paints need to be able to stand up to different temperatures and a bit more moisture from rain or even snow. It’s important to find the paint that is right for the material it’s for. These are some of the better options available at the moment:
- Polar Exterior Wall Guard Smooth Masonry Paint – This is an external damp proof paint that is resistant to weather and water. Reviews for this paint are very positive and it boosts a long-lifetime. To learn more about Polar Exterior Masonary Paint Click Here
- Dulux Weather Shield – This is a masonry paint for smooth walls which makes it great for the exterior side of a wall. This one needs two coats, but 30 minutes after application it will be rainproof. This can make it much easier to paint since you don’t have to wait for perfect weather. To learn more about Dulux Weathr Shield Click Here
- Black Jack Bitumen Paint – This paint, or bitumen paint in general, is great for outside use. It provides a waterproof protective coat that is formulated to stand up to heavy rain and prolonged oxidation. This one works great on metal, wood, roof felt and even concrete, but isn’t great for brick walls on a house. To learn more about Black Jack Bitumen Paint Click Here
If damp proof paint actually works is a common question. The paint can definitely work as intended. Damp proof paint works by forming a waterproof membrane on your wall, keeping moisture out and allowing evaporation. Like most things this comes with a condition though, you’ve got to use it properly.
Damp proof paint might not be the easy fix it looks like, but in the right situation, it works well. Make sure you treat and clean the surface first. Then, apply the right paint for your surface. if done correctly, your damp proof paint should offer a decent layer of protection against damp.