Damp. It’s one of those issues that sneaks into your home, quietly at first—maybe just a cold patch on the wall or a little flaking paint. Then one day you spot mould, or worse, feel that musty smell in the air. It’s not just unpleasant. It can ruin your home, affect your health, and eat away at your wallet. So, how do you stop damp coming through your walls—for good?
In this post, we’ll break down exactly what causes damp, how to spot it, and most importantly, how to fix it. We’ll also share tips that actually work, without the jargon.
What Causes Damp in Walls?
Before you can fix damp, you need to know what kind you’re dealing with. There are three main types:
1. Condensation
This is the most common cause of damp, especially in bedrooms, bathrooms, and kitchens. It happens when warm, moist air hits a cold surface—like your walls or windows—and turns into water droplets.
Clues:
- Water on windows in the morning
- Black mould around corners or behind furniture
- A musty smell
2. Rising Damp
Rising damp is caused by moisture being drawn up from the ground through walls that don’t have a working damp proof course (DPC). Think of it like your wall acting like a sponge.
Clues:
- Tide marks on lower walls
- Peeling wallpaper or bubbling paint
- Walls feel cold and damp to touch near the floor
3. Penetrating Damp
This is caused by water getting in from the outside due to leaks, cracks or poor construction. Rainwater can seep in through damaged bricks, old render, or around windows and doors.
Clues:
- Damp patches that get worse after it rains
- Blistering plaster or staining on walls
- Mould growth on walls that aren’t near floors or ceilings
Step-by-Step: How to Stop Damp from Coming Through Walls
Let’s get straight to it. Here’s what you can do to stop damp—whether it’s from inside or outside your walls.
Step 1: Identify the Source of the Damp
You can’t treat damp if you don’t know what’s causing it. Walk around your home and check:
- Inside: Look for condensation, mould spots, or stains. Use your nose—musty smells often point to hidden damp.
- Outside: Look for cracked bricks, broken gutters, missing roof tiles, or ground that’s level with your walls.
🔍 Pro tip: External faults often cause penetrating damp, while poor airflow leads to condensation. Rising damp usually affects older homes without proper damp proofing.
Step 2: Fix the Cause—Don’t Just Cover It Up
Here’s how to tackle each type:
✦ Condensation Solutions:
- Open windows regularly
- Install extractor fans in kitchens and bathrooms
- Avoid drying clothes indoors
- Use a dehumidifier
- Add ventilation systems like passive vents or PIV units
✦ Rising Damp Solutions:
- Inject damp proofing cream into walls (creates a moisture barrier)
- Fit a damp proof membrane to block moisture rising up
- Ensure external ground levels are at least 150mm below the DPC
- Replaster affected areas with salt-resistant render
✦ Penetrating Damp Solutions:
- Repair broken gutters and downpipes
- Fill cracks in external brickwork or render
- Check and reseal window and door frames
- Apply waterproof masonry cream to brick walls
- Replace or fix damaged flashing on the roof
Step 3: Treat the Affected Walls Internally
Once the source of the damp is dealt with, it’s time to fix the damage inside.
☑️ Replastering:
Hacked-back plaster should be replaced with a breathable, water-resistant render. Avoid ordinary gypsum—it won’t cope with damp.
☑️ Damp Proof Paints:
These can help seal walls but should never be used over salt-contaminated areas. Always apply to a dry, clean base.
☑️ Tanking Slurry:
For heavy-duty waterproofing, especially in basements, apply tanking slurry. It creates a barrier that stops water dead in its tracks.
How to Stop Damp Coming Through External Walls
External walls take the brunt of British weather. To protect them:
- Apply masonry cream (damp proof injection) to make brickwork water-repellent
- Repair cracked render or pebbledash
- Keep gutters and roofs in tip-top condition
- Avoid planting large shrubs or trees close to walls—their roots can damage foundations
How to Stop Damp in Bedrooms and Living Rooms
Bedrooms often suffer from condensation, especially in winter when windows stay shut.
Here’s how to keep things dry:
- Keep a small gap between furniture and walls
- Ventilate during and after showers or cooking
- Heat your home evenly—cold rooms invite condensation
- Consider wall insulation to reduce cold surfaces
How to Use Moisture Meter Readings to Detect and Manage Damp
Before you start treating damp walls, it’s worth getting a clear diagnosis—and that’s where moisture meters come in. These handy devices can tell you how much moisture is present in your walls and whether you need to take action.
✅ What’s a Normal Moisture Reading for Walls?
In the UK, a typical internal wall should have a moisture content between 12% and 15%. This level is considered safe and healthy. You might see slightly higher readings in kitchens or bathrooms, but if levels rise above 16%, it’s a sign you could be dealing with damp.
🔍 Understanding Moisture Meter Readings for Walls
Here’s a quick guide to help you interpret the numbers:
| Moisture Reading (%) | Condition | What It Means | Action Needed |
|---|---|---|---|
| 0 – 10% | Dry | No moisture issues. | None |
| 11 – 16% | Slightly Damp | Possibly condensation or minor leaks. | Monitor; improve ventilation. |
| 17 – 20% | Moderately Damp | Early signs of dampness. | Investigate the source. |
| 21 – 25% | Damp | Damp is present and may cause damage. | Take action quickly. |
| 26%+ | Very Damp | High risk of structural or mould issues. | Call in a professional. |
DIY or Professional Help?
You might be able to handle small condensation problems yourself with better ventilation and a dehumidifier. But rising or penetrating damp? That’s where professionals come in.
👉 If you’re dealing with damp that keeps coming back, looks serious, or affects your health, don’t leave it to chance.
FAQ
❓ How to stop moisture from coming through walls?
Start by identifying whether it’s condensation, rising damp or penetrating damp. Then take action—improve ventilation, repair leaks, or install proper damp proofing solutions.
❓ How do you damp proof an inside wall?
Use a damp proof membrane, inject damp proof cream, or replaster with a water-resistant render. Always sort the root cause first.
❓ How to treat damp walls before painting?
Make sure the wall is fully dry. Remove loose paint or plaster, treat salts or mould, and apply a suitable primer before repainting.
❓ How do you permanently fix damp?
You must tackle both the source and the symptoms. This could mean fixing leaks, injecting damp proofing cream, installing membranes, and replastering damaged areas.
❓ Can I treat damp walls internally myself?
Yes—if it’s minor condensation. But if it involves rising damp, structural repairs or persistent mould, it’s best to call in professionals.
Final Tips to Keep Damp Away for Good
✅ Keep your home well-ventilated year-round
✅ Inspect gutters, pipes, and roofs every season
✅ Make sure external ground levels are below the DPC
✅ Watch out for signs of mould or musty smells—early action saves money
Ready to Transform Your Home?
Don’t let damp take over your home. If you’ve spotted signs of damp, or just want peace of mind, it’s time to act.
Contact the experts at Damp and Mould Solutions Ltd. today.
We’ll inspect your property, find the root cause, and give you a lasting solution—not a quick fix.
📞 Call us at 020 4542 6114
📧 Email us at [email protected]
Let’s turn your home into a drier, healthier, and more comfortable space.