How to Damp Proof a Wall

Damp is a very common problem in properties in the UK, and it can be really detrimental if left untreated. If you're a landlord, homeowner or have any responsibility over a property, keeping away damp and mould growth should always be a priority!

With insights from Drycore here's what you need to know about damp proofing your own wall, and what you'll need to do.

What is damp?

Damp occurs when there is excess moisture on the surface or inside the walls. It can form on internal walls and external walls. There are lots of different causes and types of damp, and each type causes different levels and types of damage. The main types of damp that you will experience in a property are:

Rising damp

Rising damp is identifiable by the tide marks it leaves on internal walls, as well as dark patches and salts. It is caused by water and moisture being sucked up through the tiny holes in the wall in a process known as capillary action.

To damp proof a wall against rising damp, homeowners will usually have to invest in a damp proof course. This will stop the water from rising through the walls.

Penetrating damp

When building defects cause damp walls, it is known as penetrating damp. Things like defective roofing, leaking gutter and faulty downpipes can cause penetrating damp, as they allow water into your home, causing damp walls. Some properties in high wind areas may find that this also contributes to penetrating damp. On top of all of this, damaged render can also contribute to penetrating damp problems.


Some damp is caused by issues within the property, like single glazed windows, poor ventilation and certain activities within the home, such as air drying clothes or not using extractor fans. Condensation builds up on surfaces, leading to mould, mildew and every dry rot if left alone.

Why is damp proofing necessary?

When damp causes problems to the walls of a property, it can cause real structural damage. This means that, without adequate damp proofing, you run the risk of reducing the structural integrity of your property. Damp can also ruin wallpaper and paint, leading to crumbling plaster and a damaged wall finish. In addition, it can cause mould growth within the property. If left untreated, mould growth can lead to health conditions such as respiratory conditions.

How does damp proofing work?

There are two main types of damp proofing that can help to prevent rising damp in your property. If you're having a really damp issue, it's worth considering getting a damp proof course done to your home. This will essentially work to damp proof your internal walls (or external walls) and keep the excess moisture at bay. Most properties will have a damp proof course when built, but these will wear out. If you notice damp patches on your interior walls, you may need a new damp proof course.

There are, however, other types of damp proofing that are less invasive than a damp proof course. These are often favoured over splashing out on a dpc as the process can be quite time consuming.

The two types of damp proof course

Chemical damp proof course

The most common type of damp proof course is a chemical damp proof course. This method of damp proofing walls is minimally disruptive, and lasts up to twenty years, so you should not have to worry about having damp internal walls again any time soon. It's a great way of targeting rising damp, and most damp proofing experts will offer it as a service.

Chemical dpc works by injecting a chemical into the wall, just a few inches above ground level, to prevent water from being able to rise past that point.

Electro osmotic damp proofing

There is also the option of the electro osmotic damp proof course which works by creating an electrical current in the lower half of the wall by using copper and titanium wires. This charge reverses capillary action, outright turning any excess moisture away!

This type of damp proof course only lasts around ten years, but it is effective.

Other forms of damp proofing walls

If a damp proof course isn't something you have the time or funding to consider, why not try one of these options instead?

Damp proof paint

Using damp proof paint creates a sandwich layer system that keeps moisture at bay. They can be applied to the background substrate or to the plaster surface itself. You can get damp proof paints in a myriad of colours and finishes so that it best fits your style, too.

Damp proof membranes

A damp proof membrane is made from high density polyethylene, a material that is completely impervious to moisture and salts. The damp proof membrane can be fixed to internal walls after the source of the damp has been resolved. The membrane has an egg-box type shape that creates an air gap, allowing moisture to evaporate.

Damp proof membranes can be installed at home by laymen, it simply needs to be attached to the wall using a drill and the membrane fixing plugs that come with the product.

Tanking slurry

On masonry walls, brick and concrete, a tanking slurry can help with damp walls. The process is a little intense, and involves the internal walls being chipped back to original masonry. Once exposed, the masonry can then be coated in a tanking slurry that will create a waterproof layer. This layer will also be able to withstand high water pressures. This will help to combat rising damp, and penetrative damp, and can even be beneficial when damp proofing against condensation.

Water resistant render

If your plaster has been damaged by moisture on your damp walls, you can repair the plaster walls by chipping the render and plaster right back and replacing it with a water-resistant render and plaster. This will help to protect your walls from penetrating damp, and should combat rising damp reasonably well. Water resistant render can help you to win the ongoing battle against damp internal walls. It's not the most reliable form of damp proofing, but it will definitely work to stop you from having to deal with damp internal walls.

Preventing damp walls in a property

While things like rising damp can be hard to prevent without proper damp proofing, you can prevent damp walls and furniture in your property by ensuring that you try to avoid certain things and encourage others. Damp walls can be prevented by ensuring the property has proper ventilation, dehumidifiers and moisture collectors where possible, and heating where needed. These will not do much to fight rising damp on internal walls,

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