How to spot signs of damp in your house

Damp can cause a great deal of stress for many homeowners. As well as making a house feel cold, uncomfortable and unhealthy, it can destroy decor, ruin furniture and aggravate allergies and respiratory problems like asthma.

If it isn’t dealt with, it can cause severe structural damage to a building, which can be extremely dangerous. The moisture can weaken structural timbers and lead to other related problems, such as woodworm, dry rot and wet rot.

But how do you know if you have damp in your property? And if you suspect you do have damp, how do you treat it? 

In this article, we’ll explain how to spot the different types of damp, advise on what you can do to rectify the problem and give tips on how to prevent it from occurring in the first place.

How can you tell if you have damp in your house?

Telltale signs of damp include a musty smell, cold, wet or mouldy walls, floors or ceilings, excessive water droplets on windows, rotting skirting boards, lifting or peeling wallpaper, discoloured patches on walls or plaster and increased humidity in the air.

The early stages of damp can usually be identified by a musty smell — in which case, you should examine your house to locate the problem by feeling for wet patches, looking underneath the flooring and listening for a crunching sound as you move your hand over walls (as this could be plaster salts that have been washed out of the bricks and into the plaster). The best way to check for damp, though, is to call in an expert surveyor.

Continue reading to find out how to tell the difference between rising damp, penetrating damp and condensation, what the possible cause could be and what you need to do to treat each one.

What causes damp?

Damp is caused by water or moisture working its way into a building via walls, ceilings, floors or windows. This can happen in numerous ways, including:

A damaged or non-existent damp-proof course, which means moisture can rise up from the groundA leaking appliance, such as a dishwasher or washing machineBlocked or damaged gutteringBurst or leaky pipes and overflowsInadequate ventilation, meaning damp can arise from everyday household tasks, such as cooking, drying wet clothes indoors, bathing and showeringLeaking windowsMissing or broken roof tiles that allow water to get in through the roofPorous bricks

How to identify rising damp

Rising damp occurs when external moisture is drawn up from the ground through the brickwork. To prevent rising damp new buildings should have a damp-proof course built into the walls about 15 centimetres above ground level and a damp-proof membrane underneath the floor. However, these can be damaged or worn over time, making them ineffective.

If you see any of the following signs on the ground floor of your house, you may have rising damp:

Damaged or rotting skirting boards or plasterDamp patches at the base of a wall, which gradually move upwardsPeeling paint or wallpaperRusty nails or screws on skirting boardsWet and lifting floor coveringsWhite, powdery salt marks on walls and plasterYellow or brown ‘tide marks’ about one metre above floor level (though they can be higher)

How to identify penetrating damp

Penetrating damp is caused when external problems with a building lead to water or moisture finding its way in from the outside. This means you might also see signs of damp on external walls, such as damaged brickwork or moss and algae.

Some of the most common external problems which lead to penetrating damp include:

Blocked or damaged gutteringBroken or porous brickworkBurst or leaky pipes and overflowsCracked or defective external renderDamaged window and door sealsDefective roof coveringsMissing roof tilesPoorly maintained drainsTired or defective mortar jointsVegetation interfering with the rainwater system and wall surfaces

The extent of the problem depends on what’s causing the damp. For example, a leaky pipe is easier to deal with than porous brickwork, which will be more widespread.

Some of the signs of penetrating damp are similar to rising damp. However, you’ll usually notice that the moisture moves horizontally through the walls rather than up:

Bubbling plaster or wallpaper lifting or peelingCracks or damage to the external walls or gutteringDamage to the wallpaper or plaster higher up the wallsDamp patches in various places on the walls and ceiling

How do I know if I have damp or condensation?

Condensation is actually a type of damp, which occurs when air condenses on cold surfaces and creates water. It’s often caused by carrying out everyday household tasks without having adequate heating or ventilation in your home.

If you experience any of the below around your home, it could indicate a condensation problem.

A lingering musty smellBlack mould around window frames or on walls, particularly behind furniture on external wallsDamp patches on wallsExcessive moisture or water droplets on cold surfaces like windows, cold walls and tilesIncreased humidityWater running down walls in rooms where there’s steam, such as bathrooms and kitchens

How do you fix a damp internal wall?

If you find a small patch of damp on a wall or notice some black mould around the window in the bathroom, it can be tempting to put it on the back burner until you have time to fix it. But not dealing with it immediately can lead to more serious structural problems to your house that you may find you won’t be able to claim on your home insurance. This is because damp or mould treatment is often seen as “general wear and tear” that can occur in a property, rather than an unexpected issue that can be covered by insurance.

When you buy a home insurance policy, you’ll usually need to agree that the property is in a good condition and declare whether or not there’s damp. If there is, and you don’t declare it, it will mean the property is not in a good condition, and your policy will be invalidated. So it’s always best to deal with the problem as soon as possible.

The first thing you need to do is to diagnose the problem correctly. Different types of damp need to be treated in different ways, and if you use the wrong treatment, it could lead to more issues and become more expensive to fix. Once you’ve diagnosed the problem, you can decide whether to attempt to fix it yourself or hire a professional.

While most damp problems do require expert help, some can be fixed by some simple home maintenance:

Eliminate condensation by improving the ventilation in your home 

It’s easy to do this by: 

Cleaning out airbricks in the wallsCooking with pans that have lidsHanging washing outside or in a room with the door closed and window openInstalling extractor fans in bathrooms and kitchensOpening more windowsRunning a bath with cold water first, then hot (this reduces up to 90 per cent of the steam that leads to condensation)Using dehumidifiersVenting your tumble dryer to the outside

Tackling rising damp and penetrating damp

This is less easy to do, but as long as you’ve identified the problem correctly, you can try:

Locating your home’s damp-proof course and checking that it’s not buried beneath paths and flower bedsRepairing or replacing cracked renderReplacing or repairing missing roof tilesReplacing porous bricks or painting them with silicone water-repellent paintUnclogging and repairing or replacing gutters and drainpipes that are blocked or leaking to prevent moisture and water from penetrating the outside walls

If you’re certain you can locate and rectify the source of the damp, you have a good chance of being able to resolve the problem yourself. However, if you’re unsure of what type of damp it is, what caused it, the extent of the damage or the solution you need, you should speak to a reputable contractor.

How much does it cost to fix damp in a house?

Fixing minor damp problems in your home yourself can be relatively inexpensive. But — as mentioned above — you need to make sure you’ve identified the problem, cause and solution accurately. If the damp isn’t going away after you’ve tried the above fixes, or you’ve realised the problem is too big to rectify yourself, you’ll need to hire an expert. This may seem expensive at the time, but it will be worth it in the long run, as damp that leads to rot can cause structural damage, which is much more expensive to fix.

As stated earlier, the extent of the problem depends on what the cause is. One leaking pipe is less costly to repair than replacing multiple porous bricks. Some of the other, more expensive solutions a professional may suggest include:

Fitting or replacing a cavity tray to prevent water from outside reaching the inner wallFitting or replacing a damp-proof course and membrane, which involves materials or chemicals being injected into the wall to create a water-proof barrier

The cost of damp-proofing your house depends on factors such as its size, age and whether there are any existing damp issues. However, to give you an idea, a good quality extractor fan is roughly £500, and a remedial damp-proof course plus related plasterwork for a flat, five-metre wall costs from £1,200.

When hiring a professional, costs can run into thousands of pounds, so it’s well worth shopping around for at least three quotes before hiring someone. When choosing a tradesperson, you should consider their qualifications (Certified Surveyor in Remedial Treatments (CSRT) and Certified Surveyor in Structural Waterproofing (CSSW) qualifications assure that the survey and treatments are being carried out to the highest industry standards), whether they’re members of recognised industry associations like the Property Care Association (PCA), how many positive online reviews they have and whether they’re able to competently answer the questions you have and tailor their services to suit your needs. It’s also a good idea to ask for recommendations from friends, family, neighbours and local community groups.

How can you prevent damp in your house?

Because most home insurance policies don’t cover damp, it’s wise to make sure you take measures to prevent it from occurring in the first place.

Here are some of the ways in which you can do this:

Allow air to circulate by leaving gaps between walls and furnitureDry clothes outside when possible and keep lids on pans when cookingOnce you’ve rectified a damp issue, remove any mould that’s built up with a cloth and soapy water or anti-mould sprayOpen windows and vents and use extractor fansMaintain guttering, drains and roof tilesRegularly check the inside and outside of your building, paying particular attention to bathroom and kitchen walls and behind furnitureRemove moss and algae that’s growing on external walls

Summary

There are three different types of damp: Rising damp, penetrating damp and condensation. Telltale signs of rising damp include damaged or rotting skirting boards or plaster, damp patches at the base of a wall, which gradually move upwards, peeling wallpaper and rotting skirting boards. Some of the signs of penetrating damp are similar to rising damp — such as peeling wallpaper and damp patches on the walls — however, you’ll usually notice that the moisture moves horizontally through the walls rather than up. If you experience a lingering musty smell, black mould around window frames or on walls, excessive water droplets on windows and walls or increased humidity, it could indicate a condensation problem.

It’s important to deal with damp immediately, as it can lead to more serious structural problems to your house that you may find you won’t be able to claim on your home insurance. Different types of damp need to be treated in different ways, though, and if you use the wrong treatment, it could lead to more issues and become more expensive to fix. Once you’ve diagnosed the problem, you can decide whether to attempt to fix it yourself or hire a professional.