How to Damp Proof a Garage?
How to identify the type of damp in your garage and sort it out for good.
Damp in a garage is a frustrating problem, and it’s rarely a one-size-fits-all fix. The right solution depends on what’s causing it. Whether you’re dealing with condensation, rising damp, or water coming in through cracks and walls, getting to the root of it first saves you time and money. Here’s how to work it out and what to do about it.
At a glance
- The solution depends on the type of damp: condensation, rising damp, penetrating damp, or water ingress.
- Condensation is the most common and can usually be tackled with better ventilation and insulation.
- Rising damp needs a damp proof membrane (DPM) or chemical damp proof course (DPC).
- Penetrating damp requires fixing the external cause, repointing, gutters, seals, or render.
- Most home insurance policies won’t cover gradual damp. Sudden water damage from a burst pipe is a different matter.
Types of garage damp
Before you do anything, work out what you’re dealing with. The four main types are:
| Type of damp | What causes it |
|---|---|
| Condensation | Warm, moist air cooling on cold surfaces, common in poorly ventilated garages |
| Rising damp | Moisture travelling up from the ground through walls and floors where there’s no damp proof course |
| Penetrating damp | Water seeping through external walls due to damaged brickwork, gutters, or render |
| Water ingress | Water entering through cracks or gaps in floors, walls, or door frames |
Identifying your damp problem
A thorough inspection of your garage will usually point you in the right direction. Here’s what to look for:
| Signs | Likely type of damp |
|---|---|
| Water droplets on surfaces, steamy windows, black mould patches | Condensation |
| Tide marks rising up walls, peeling paint or plaster | Rising damp |
| Localised wet patches on walls, particularly near corners or external doors | Penetrating damp |
| Pools of water on the floor after rain | Water ingress |
If you can’t pinpoint the source yourself, a damp surveyor can give you a definitive diagnosis and recommend the right course of action before you spend money on the wrong fix.
DIY damp proofing solutions
Condensation
Condensation is the most common type of garage damp and usually the most straightforward to address.
- Improve ventilation. Install an extractor fan or add vents to keep air moving through the space. Our guide on how to prevent damage from poor ventilation covers why this matters.
- Insulate walls and ceiling. Thermal insulation reduces the temperature difference between the air and surfaces, which is what causes condensation to form.
- Use a dehumidifier. A good way to bring moisture levels down quickly, particularly during wetter months.
- Apply anti-condensation paint. Helps prevent moisture from settling on walls as a short-term measure.
Rising damp
Rising damp needs a physical barrier to stop moisture travelling upward through your walls and floors.
- Lay a damp proof membrane (DPM). Installed beneath flooring to stop moisture rising from the ground.
- Inject a chemical damp proof course (DPC). Creates a horizontal barrier within the wall to stop water climbing. This can be done as a DIY job for smaller areas, but a professional is worth considering for anything more extensive.
- Apply tanking slurry. A waterproof coating applied directly to walls to create a sealed layer.
Penetrating damp
Penetrating damp is caused by an external problem, so the fix needs to start on the outside.
- Repoint the brickwork. Fill gaps between bricks to block the water pathways.
- Fix gutters and downpipes. Damaged or blocked gutters direct water onto your walls rather than away from them. Our guide on how to clean gutters covers the basics.
- Apply waterproof render or masonry paint. Protects exterior walls from rain and moisture penetration.
- Check and replace garage door seals. Worn seals are a surprisingly common entry point for water.
Water ingress
- Install a damp proof membrane. Protects the floor from moisture entering through the ground.
- Seal cracks. Fill any gaps in walls, floors, or around door frames with an appropriate filler or sealant.
- Apply a waterproof screed. Adds a durable, moisture-resistant surface to your garage floor.
For example:
A homeowner notices pools of water forming on their garage floor every time it rains heavily. They assume it’s rising damp and lay a new membrane, but the problem persists. A closer look reveals a crack running along the base of the wall where water is entering directly. Sealing the crack properly resolves it. Identifying the right type of damp first saves time, money, and a wasted fix.
When to call a professional
If the problem is widespread, keeps coming back, or you’re not confident tackling it yourself, a damp specialist is the right call. Professional options include:
- Full DPC or DPM installation
- Tanking slurry or membrane application for serious damp
- Structural repairs like repointing or screeding
Costs vary depending on the scope of the work, but typically range from £300 to £3,000. Most professional jobs come with a guarantee, which is worth factoring in when weighing up DIY versus calling someone in.
Damp proofing a garage conversion
If you’re planning a garage conversion, building regulations require proper damp proofing to make the space habitable. You’ll typically need to:
- Install insulation and adequate ventilation
- Damp proof both walls and floors with a membrane or tanking solution
- Fit high-quality seals to windows and doors
Budget between £1,000 and £3,000 for professional damp proofing as part of a conversion, depending on the size and condition of your garage.
Insurance Coverage and Limitations
Most home insurance policies, including buildings insurance, won’t cover gradual damp. Insurers treat it as a maintenance issue rather than a sudden, unexpected event.
However, sudden water damage caused by something like a burst pipe is a different matter and is typically covered. For more on how home insurance handles damp and mould, it’s worth checking your policy wording carefully so you know where you stand before you need to make a claim.
If you store valuables in your garage, it’s also worth checking whether they’re covered under your contents insurance. Not all policies extend cover to outbuildings as standard.
Before we go
Tackling damp in your garage starts with identifying the type correctly. Get that right, and the fix becomes a lot more straightforward. For minor condensation issues, better ventilation and insulation can make a significant difference. For rising damp or penetrating damp, you may need to go further, and there’s no shame in bringing in a professional if the problem is beyond a DIY fix.
Lemonade’s home insurance covers sudden and unexpected events, so make sure your policy is up to date and reflects what you actually need.
Damp proofing garage FAQs
How can I tell what type of damp I have?
Look at where the damp appears and what it looks like. Condensation tends to show as water droplets or black mould on cold surfaces. Rising damp leaves tide marks climbing up walls, often with peeling paint or plaster.
Penetrating damp creates localised wet patches on walls, particularly near corners or external doors. Water ingress usually shows as pooling on the floor after rain. If you’re still not sure, a damp surveyor can give you a definitive diagnosis.
What’s the cheapest way to fix condensation in a garage?
Improving ventilation is usually the most cost-effective starting point. Adding vents or installing an extractor fan helps airflow and reduces moisture build-up.
A dehumidifier is another affordable option for bringing humidity levels down quickly. Anti-condensation paint can help as a supplementary measure, but ventilation is the more effective long-term fix.
Can I do a DIY damp proof course?
Yes, chemical DPC injection kits are available for DIY use and can work well for smaller or more accessible areas. For larger or more complex jobs, a professional installation is a better option and usually comes with a guarantee. Getting the application right is important, as a poorly installed DPC won’t stop rising damp effectively.
Will damp proof paint fully fix penetrating damp?
No. Damp proof paint can act as a temporary barrier, but it won’t resolve the underlying cause. Penetrating damp needs to be fixed at source, whether that’s repointing cracked brickwork, repairing gutters, or replacing damaged render. Apply the paint after fixing the cause, not instead of it.
Does home insurance cover damp proofing costs?
Generally not. Most insurers classify gradual damp as a maintenance issue, which falls outside the scope of a standard home insurance policy. Sudden water damage, such as a burst pipe, is typically covered. Check your policy wording carefully, and if you’re unsure, contact your insurer directly before carrying out any work.
Share
