Comparing Rising Damp and Penetrating Damp: Different Causes and Remedies

Comparing Rising Damp and Penetrating Damp: Different Causes and Remedies

4th September, 2023

There are many different types of damp. Two of the more serious ones you may encounter in your home are penetrating damp and rising damp. Many people confuse the two but as the remedies for both are different it is important to know the difference so that you can treat them accordingly and rectify your damp problem.

What Is Penetrating Damp?

Penetrating damp is usually found in the higher sections of your wall or on your ceiling. It may occur either inside or outside your home. The tell-tale signs of penetrating damp are damp patches or stains on your walls or ceiling. These often get darker when it rains as more damp seeps through the walls. This can cause the paint on your walls or your wallpaper to become damp and you may notice it peeling or blistering. It will move horizontally across walls and ceilings. You may also notice an unpleasant musty smell.

How Does Penetrating Damp Occur?

There are two different types of penetrating damp, normal and lateral. Normal penetrating damp is usually caused by parts of your home becoming defective and letting water penetrate, which causes damp in your home. It commonly occurs because of faulty guttering, roofing, brickwork, and around doors and windows.

One common way of normal penetrating damp appearing in your home is through leaks. Checking pipes and water sources can often be a good place to start when trying to identify the cause of the problem.

Lateral penetrating damp is usually caused by a missing or defective damp course or high soil levels. This is more likely to occur in older-style homes as they were designed to breathe rather than keep moisture out. Many old cellars were designed to create a cold store in the home and stop rising damp occurring with little thought to the increase in penetrating damp this could cause.

How To Treat Penetrating Damp

You can often use preventative measures to ensure this problem doesn’t occur in your home. Keeping on top of maintenance issues is the key here. Clean out your gutters and downpipes regularly, fix leaky taps, replace cracked roof tiles, and repair any porous brickwork on the outside of your property or cracks in your windows. You may be able to carry out a lot of this work yourself, however, even if you do need to call in the experts such as a roofer or plumber this can work out considerably cheaper than having to fix a penetrating damp problem.

Once you have fixed the problem you can use treatments such as silicone or damp-proof paint to prevent the problem re-occurring in the future.

What Is Rising Damp?

In contrast, rising damp rises from the ground and is usually found at low levels such as the bottom of your walls on the ground floor. It is less common than penetrating damp, but it can be more difficult to carry out preventive measures on rising damp than penetrating damp, as it is harder to notice in its early stages. Once you have spotted it you will notice that it travels vertically up your wall. This differs from penetrating damp, which travels horizontally.

You may not become aware of the problem until you notice the bottom of your wallpaper peeling or your paint flaking. It can also affect timber such as hardwood or laminate flooring or your skirting boards, and you may notice that these start to rot because of the water damage. You may notice tide marks on your walls, and they will feel damp to the touch. The odour from rising damp is the same as the one from penetrating damp, so it is impossible to tell the difference through smell.

How Does Rising Damp Occur?

Rising damp occurs when groundwater seeps into your brickwork through tiny porous holes in your bricks and makes its way up the walls. This water contains salt, which is why you often see tidemarks appearing in your home. Gravity ensures that the water can only be sucked up so far which means that you are unlikely to see rising damp above about a metre above your floor.

You may also see rising damp signs on the outside of your property. The warning signs here are low-level crumbling brickwork or tide marks.

Modern houses are built with a damp-proof barrier to prevent rising damp from occurring. This is made from water-resistant material. It has been a legal requirement for builders to use damp-proof coursing since 1875. However, damp-proofing can suffer from general wear and tear making it less effective over time. Also, if your home was built before 1875 it may not contain a damp-proof course at all. This means that you are more likely to suffer from rising damp if you own an older property.

How To Treat Rising Damp

Rising damp can be a serious problem because it can lead to structural issues in your home. As is the case with penetrating damp, it is important to identify the source of the water ingression before treating the problem to stop it from recurring. This can be harder to spot than penetrating damp so it may be best to call out a damp-proofing expert to do this for you.

Once the cause of the problem has been identified, you can try using a damp-proofing cream to rectify it. This is injected into specially positioned holes in the mortar course. It is a liquid that is absorbed into the bricks to close any holes and stop water from getting in.
To treat internal walls, you will need to strip the wall back to the brickwork before injecting the cream. Once you have done this you can then replaster and redecorate your wall.

If in any doubt about the type of damp, the source, or the best way to treat it, you should call in the experts. Leaving the problem can make it worse and costlier.

Alternatively, a damp-proof membrane could be used to provide a new damp-proof course. However, this is a much more complicated process, and you will likely need to hire a specialist to do this for you. That being the case, we encourage you to call us to discuss your options if you have rising damp.