How to treat damp walls internally

Internal walls becoming damp can be a problem for the look of your home, your health, and the structural integrity of the walls themselves.

So, what can you do about it?

First, you need to understand the different types of damp to understand why you have damp issues to begin with.

After that, we’ll talk you through what you need to do to treat damp walls in your home and then complete a damp proof course to make sure it doesn’t return.

Identifying damp

The three major forms of damp you’ll need to know about for damp internal walls are:

  • rising damp
  • penetrating damp
  • condensation damp

Knowing the differences among these three is essential, so you can take the right steps to remove it and prevent it in the future.

Rising damp

Identifying rising damp is easy because you’ll notice that the damp problem starts at the bottom of the walls. When groundwater rises, you might notice damaged skirting boards, damp floor boards, or cracking chimney breasts to begin with, as the damp or mould growth continues.

The most common mould growth you’ll notice with rising damp is black mould growth because black mould only forms when there is extreme moisture. You might also notice ‘tide marks’ which show discoloration up to 1m in height. Remember, too, that this type of damp only occurs on the ground level.

Rising damp on internal walls is one of the most common forms of damp, and it’s usually caused by the damp proof course.

With rising damp, it’s common for the damp proof course to have been installed poorly, or else grow old and perform poorly later, allowing damp patches to form.

Water is very good at finding its way into our homes when damp proofing is failing. It’s also really common for rising damp to make its way through the damp proofing at structures adjoined to your home such as steps or a newly installed patio.

Often when these structures are installed, they can cause cracks and tears in the damp proofing, which will then cause damp internal walls.

If you’re unsure if your damp problem is caused by rising damp or something else, look at the external walls on the opposite side of the damp internal wall you’ve noticed. External walls will often suffer from damp problems too if it’s rising.

Penetrating damp

Another problem you may face is penetrating damp. This is more of a unique type of damp because it isn’t to do with the damp proofing, but instead because of the bricks used in the house’s construction.

The external walls’ bricks can cause damp on internal walls because sometimes bricks can be porous, allowing water to soak through the bricks of the outside walls and then affect the internal wall too.

Rain penetration is the biggest sign here, because you’ll notice that the problem gets worse when it’s raining continuously or there’s a bad patch of heavy rain.

Condensation damp

This is the most common type of damp because condensation is simply caused by excess moisture, poor air flow, and poor ventilation.

Unsure if you have damp caused by condensation? Often, this can be felt by simply touching the damp wall. You might also notice a musty smell, too.

This type of damp happens when moist air isn’t circulating properly in a room, and the interior walls will be especially affected by warm moist air in the home. This warm air is common in kitchens and bathrooms, and if ventilation isn’t up to scratch here, condensation will form and the water droplets will cause damp.

You might also notice a worsening of the problem in winter, where warm air from inside and cold air from outside clash and more condensation is formed around the window frames and surrounding walls.

Treating damp

Now that you know the different types of damp that affect internal walls, let’s talk about treating them!

Treating rising damp

Since the problem here is with the damp proof, when you treat rising damp, you’ll need to patch it up, or else get the whole damp proof redone by professionals. When there’s significant damage, you’ll also need to think about replacing floorboards, skirting boards, and anything else suffering from wet rot.

If you simply need to replace the damp proof, then damp proofing walls is possible to do without investing in full damp proof courses.

How to damp proof yourself

A new damp proof course could cost a lot, but if the damp patches are only small, then you might just have a small area that needs damp proofing to remove your damp problems.

Here’s what to do:

  • Drill through the internal walls and external walls in the area that needs damp proofing.
  • Check the damp proof course you’re using to make sure you drill the correct size holes in the correct pattern.
  • Use a pump to push damp proofing cream into the holes. This creates a damp proof membrane that stops water from getting in.
  • Fill the holes with mortar.
  • Allow to dry, and then apply finishing touches (paint walls, reapply wall coverings, etc.)

Treating penetrating damp

Penetrating damp is similar in that you will need to do a damp proof course again, but the focus this time is on the exterior walls rather than the interior walls.

The damp on internal walls you’re noticing here is caused by the external walls being porous, which then affects the inner surface.

To cure damp here, just complete a damp proof course again and make sure the damp seal you use is high quality so bricks don’t let water in.

Treating damp caused by condensation

When you feel damp walls, the damp patches may be caused by condensation, which can lead to unwanted mould growth.

Check for cold walls and cold surfaces. A cold surface might mean poor thermal insulation, which will need to be fixed to prevent further deterioration.

Look at double glazing and, if you can afford it, update old buildings with the necessary work to stop damp from forming because of condensation.

This will mean better airflow and ventilation, so condensation and moisture don’t build up and create damp walls.

Final message

All damp can be treated. The trick is knowing what damp you have so you can fix the damp walls appropriately, deal with the moisture, and prevent serious damage to your home and harmful respiratory conditions caused by the damp.

Inappropriate treatments can cause unnecessary expense, so make sure you’re certain of the type of damp you have before you attempt to fix it.

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