Key Takeaways

• Identify the Cause: Determine whether the dampness is due to rising damp, penetrating damp, or condensation. Each type requires a different approach.
• Repair External Defects: Fix any cracks in the render, damaged pointing, or broken roof tiles that may allow water ingress.
• Install or Repair Damp Proof Course (DPC): Ensure the DPC is intact and functioning to prevent moisture from rising through the walls.
• Improve Drainage: Ensure gutters and downpipes are clear and direct water away from the building’s foundation.
• Apply Protective Coatings: Use breathable water-repellent treatments to protect the external walls without trapping moisture inside.

Did you know that over 4 million homes in the UK suffer from some form of damp, with penetrating damp being one of the most common culprits?

This kind of damp isn’t just an ugly sight – it can ruin your property’s structure, damage the interiors, and affect your health too!  If the issue is not managed, it gives way to mould, damages brickwork, and results in expensive repairs.

The initial step to stop damp coming through external walls is identifying its signs, which include: 

• Peeling Paint – Paint lift-up and cracks due to the presence of moisture.

• Mould and musty smell – Mould and unpleasant smells thrive in humid conditions. 

• Damp patches/Water stains – A noticeable discolouration rests on the walls due to water ingress. 

• Efflorescence – A form of whiteness left over due to evaporating moisture. 

• Crumbly plaster – Dampness weakens plaster, turning it into a soft or flaky powdery state. 

If not cared for, these signs tend to make the problem worse, but some remedies help manage such issues best. 

This detailed discussion focuses on identifying the root causes of the outer wall damp problems, finding solutions, and most importantly discovering preventive measures. 

Understanding the Causes of Dampness in External Walls

Outer walls on a property can be damp for different reasons, such as:

• Rainwater Ingress: This happens when rainwater finds its way to the walls. It can happen through spaces, holes, and even old masonry.

• Rising Damp: It occurs when water from below the ground rises to the wall via capillary action.

• Inadequate Drainage: Clogging of the gutter, as well as poorly designed drainage systems, can cause water accumulation on the bottom of the property leading to dampness issues.

Solutions for Dampness from External Walls

Now that you understand the signs and causes of dampness in exterior walls, how can you stop it? Here are several ways: 

1. Repairing and Waterproofing the Exterior

Inspecting and Fixing Cracks and Gaps: Scrutinize the surface of your outer walls for cracks, gaps, or breakages. If you find any, fill them with cement/masonry cream. No more moisture will leak through.

Repointing Brickwork: Re-pointing is a method in which an old mortar is raked out, and a fresh, waterproof mortar is put in to seal the brickwork. It eliminates the possible causes of dampness in outer walls.

Applying Waterproof Sealant or Coating: Use silicone-based sealants or masonry protection creams. They work well to prevent water from being absorbed.

Painting With Weatherproof Exterior Paint: Add weather-resistant and wear-resistant paint on top of the existing layer to increase protection.

2. Improving Drainage and Guttering

Check and Clean Gutters and Downpipes: The removal of unwanted debris from your gutters and downpipes should be routine. Doing this will ensure that they are clean and therefore, there is no blockage in the water flow. 

Ensure Proper Ground Drainage: Make sure that your property has proper ground drainage; that is, to direct water away from the foundation. It requires a landscaping modification and installation of proper drainage channels.

Install a French Drain: A French drain should be installed to keep groundwater from getting to the building’s foundation. It is made by a trench filled with gravel and has a perforated pipe buried in the soil to carry water away from the building.

3. Installing or Repairing a Damp-Proof Course (DPC)

Check the presence of DPC: Check for an existing DPC in your walls by visual inspection. It is usually a horizontal layer of waterproof material. In case it is not properly attached or is not there, then make sure to fix a good one.

Inject a Chemical DPC: Involves getting some water-resistant fluid to the walls at the right level. This liquid will then serve as a guard against moisture coming up and is a cheap DIY resolution if you have just enough know-how and tools to operate.

Install a Physical DPC: For more severe cases, a physical DPC, such as a plastic membrane, may be required. This method is more effective but typically requires professional installation.

4. Enhancing Internal Protection

Use Damp-Resistant Plaster and Paint: To prevent or even remove dampness and mould, choosing an internal plaster and paint with moisture-resistant properties is a good approach. It will block moisture and safeguard the walls.

Improve Ventilation: Use extractor fans or air bricks in moisture-prone areas to maximize airflow. Effective ventilation helps to lower the moisture and avoids condensation. 

Install an Internal Membrane System: In extreme instances, waterproofing the affected wall with a membrane that separates the damp wall from the interior space helps. 

Preventive Maintenance Tips

• Regularly monitor your gutters, walls, and drainage features so you can solve any issues at hand.  

• To help reduce the chances of moisture build-up, keep plants and soil away from the outside walls.  

• Make certain that there is proper airflow in your home to control condensation, which might cause dampness.

When to Call a Professional

Although a lot of moisture problems can be sorted out through do-it-yourself techniques, a few circumstances may require professional services:

• If your attempts to get rid of moisture have been futile.

• Where the problem involves too much damage to the structure or other complicated issues from dampness.

• If you are not a professional, do not have the right skills and tools, or have never dealt with dampness before.

Frequently Asked Questions  

How can I tell if my external wall has a damp problem?
Look for signs such as damp patches, peeling paint, or mould growth on the interior walls.

Is it safe to use sealants on external walls to prevent damp?

While sealants can provide a temporary barrier, they may trap moisture inside the wall. It’s better to address the root cause of the dampness.

Can I prevent damp by painting the exterior walls?

Using breathable, damp-resistant paints can help protect the walls. However, ensure that the underlying issues causing the dampness are resolved first.

Should I consider external wall insulation to prevent damp?

External wall insulation can be effective, but it should only be applied after addressing any existing damp issues to prevent trapping moisture within the wall.

When should I consult a professional about damp in external walls?

If you notice persistent dampness despite taking preventive measures, it’s advisable to consult a damp specialist for a thorough inspection and appropriate treatment.