Damp Proofing for External Walls

How can you tell if you have damp issues and what effect does damp have on my home?

There are easy signs to look out for to identify if you have damp in your home:

– The rooms will smell musty and damp

– You’ll see mould and mildew on affected walls, ceilings or floors

– The walls will feel cold and damp

– There may be discoloured patches on plaster or walls

– Condensation on windows

They are just a few indicators that you may have a damp problem.

Left untreated, damp in the home can bring with it an array of associated issues.

It risks impacting on physical health, can damage furniture, walls and floors, and can cause you to spend more money on energy.

All of these make it essential to combat it effectively and quickly.

What causes damp in external walls?

When proofing your home, there are two types of damp you need to understand; rising and penetrating.

They are distinct, and how you tackle it will depend on the kind of damp you’re faced with.

You should also check, before considering damp proofing your home, if there is a damp proof course (or DPC) installed already.

You’ll be able to tell; if there isn’t, then you’ll see salts on the inside walls.

These make up a crystallised powder that shows up on plaster in the home if there isn’t a form of protection against it.

The plaster will need to be removed and a new course installed in its place.


Rising damp

Rising damp happens when moisture from the ground moves through the walls through capillaries.

Water from below the ground carries with it salts that can cause further damage – in the form of wet rot in timber and plaster – if left untreated.

It causes the paint and plaster to deteriorate, which is usually the first sign of a problem.

You might also see salts on the surface.

On an external wall the mortar can occasionally crumble, and the white salt stains will show up clearly.

When diagnosing rising damp on an external wall, you should also look out for tide marks.

Rising damp is often caused by a failed DPC, which can be the result of ground floor external floors being raised above it.

It is best treated using a damp proofing injection cream injected into holes within the wall.

The cream turns to liquid, allowing for total absorption.

Once the cream cures, it results in a strong water-resistant and repellent barrier.

It is a cost-effective option too.

Alternatively, you could install a damp-proof membrane that essentially acts as a DPC.

Penetrating damp

Penetrating damp, also known as condensation, presents itself as black mould or mildew on the wall.

It often comes with a musty smell, and is caused by water seeping into the property from outside.

It is likely caused by defects in the building, or degradation of materials the property is made of, which results in them becoming porous.

Penetrating damp can often be diagnosed by stains on external walls or damp patches on walls or ceilings.

You may also see crumbling plaster, marks of black mould congregating in a single area, drips or puddles.

As soon as you see signs of penetrating damp, you should attempt to find a solution with a licensed installer.

The method used to treat penetrating damp often depends on the severity of the damp issue.


Damp proofing external walls

There are several proofing options for external walls available.

Firstly, there is a brick waterproofer that helps the brickwork to breathe and permits damp to evaporate and in turn dry the wall.

You could also choose to install wall insulation that reduces water absorption.

It’s usually a hydrophobic coating that repels water and protects the walls from dirt, algae, pollution, oil and other issues.

It’s a long-lasting solution, making it ideal for homeowners that want to sell their property or live in it for a while longer.

It can also increase the value of your house.

You could also use a damp-proof membrane, or DPM, that acts as a barrier between the slab and the floor.

Another possibility is a damp-proof course (DPC) that is usually installed into a wall to tackle rising damp.

The DPC, a versatile and long-lasting solution, is injected into masonry, and enters small capillaries and pores in the material.

It has a low density, so it moves water inside, before curing.

However that is separate to the masonry’s drying process.

How Much Does it Cost to Damp Proof a Wall?

Rising damp treatment costs depend on the scale of your problem, the root cause and size of the building. To calculate the cost of a damp proof course for your home, you will need to first consider the size of your home and the thickness of the walls.



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