Types of Damp | How to Get Rid of Damp

Dampness in houses is more than a minor issue; it leads to serious structural problems and health concerns. Untreated dampness weakens a building’s structural integrity by causing metals to rust, wood to rot and plaster to deteriorate. Not only that, but it creates an ideal environment for mould to grow. When mould spores release into the air, they pose a significant health risk to the home’s occupants. This makes identifying and addressing the causes of damp crucial for maintaining a safe living environment. In this guide, we’ll be covering common causes of damp and the different damp treatments available.

What happens if damp is left untreated?

If you don’t stop damp, it can lead to pests, mould, decreased property value, structural issues and poor health of those living with the dampness. The longer you leave damp untreated, the worse these problems become.

Pests	Damp areas attract pests including termites, mould mites, cockroaches, and rodents, which seek moisture and shelter.
Wood decay	Timber rots and weakens when it absorbs moisture. In particular, wooden supporting beams and flooring can become compromised in the damp, leading to unsafe buildings.
Electrical faults	Moisture can corrode electrical wiring and components. This increases the risk of electrical fires and short circuits.
Mould growth	Damp environments produce the ideal growing conditions for mould, which can spread rapidly on walls, floors and ceilings. To learn how to treat mould, see our guide on Preventing and Removing Mould.
Deterioration of insulation	Moisture reduces the thermal efficiency of insulation. This leads to heat loss and increased energy consumption. To find out more about effective insulation, read our Insulation buying guide.
Structural damage to the foundations and walls of a property	Prolonged moisture exposure weakens building materials. This can cause cracks in the walls and building foundation, compromising the structural integrity.
Unpleasant odours	Dampness leads to unpleasant musty smells that are difficult to remove, leading to uncomfortable living spaces.
Peeling paint and wallpaper	Dampness causes paint to bubble and wallpaper to peel, leaving unsightly and damaged walls.
Allergies and respiratory problems	When inhaled, mould spores can trigger respiratory issues, asthma, and allergic reactions. Those with weakened immune systems, the elderly and children should stay away from mould as much as possible.
Decreased property value	Because of the long-lasting problems damp causes, visible damp issues and their associated problems significantly lower the market value of a property.

What are the different types of damp?

There are 3 types of damp commonly found in homes, each with separate causes and characteristics. To effectively treat damp, you need to understand the different types to recognise which one(s) you have. The main types of damp include rising, penetrating, and condensation.

Rising Damp: Rising damp occurs when moisture from the ground travels upwards through the walls of a building. The damp moves by capillary action. This process occurs when porous building materials (like mortar and bricks) absorb water from the soil around a building’s foundation. The water then evaporates through the building materials and into the property.
Penetrating Damp: Penetrating damp happens when water enters a building from the external walls or roof, bypassing any moisture barriers in place. This type of damp is also called lateral damp and typically occurs because of building defects.
Condensation Damp: This is the most common form of damp in homes. Condensation damp is caused by moist air condensing on cooler surfaces within the building.

What is rising damp?

Rising damp is when porous building materials absorb groundwater in the soil beneath a building. This happens when the ground surrounding a property becomes saturated with water, either from rainfall, high water tables, or poor drainage. The porous building materials (like brick, stone and mortar) below ground level act like a sponge, pulling the water in and up through the walls of the building. This process is called capillary action. The capillary action leads to the damp rising several metres above ground level, which is where rising damp gets its name from. When the water reaches a higher section of wall and evaporates, it leaves dissolved salt deposits behind. These salts can further deteriorate the building.

What causes rising damp?

Rising damp usually affects older buildings but it can occur in poorly constructed new builds too. The common rising damp causes are:

Wet soil: Houses built in areas with frequent rainfall or a high water table are more susceptible to rising damp.
Faulty damp proof course: A damp proof course, also known as a DPC, is a special membrane installed to prevent moisture ingress from the ground. When there is damage to the DPC or an absence of one (such as in older homes), moisture can enter the building.
Broken building foundations: Cracks in a building’s foundation provide an entry point for water. (Cracks in walls cause penetrating damp, rather than rising damp.)
Poor drainage and guttering: Poor drainage systems, blocked gutters and blocked drains can cause water to pool around the base of a building. This leads to wet soil and a higher risk of rising damp.
Lack of ventilation: Poor ventilation does not cause rising damp, but can make the effects worse. Without ventilation, moisture becomes trapped, so the building materials cannot dry out.

What does rising damp look like?

Identifying rising damp early is crucial for minimising damage and repair costs. Common indicators of rising damp are:

Tide marks on the wall, up to one metre high
Stained wet patches on the wall (the patches usually start near the floor and rise upwards, and commonly appear as a brown sticky substance on walls)
Peeling / bubbling paint or wallpaper
Decayed skirting boards or flooring
White, powdery deposits on walls (efflorescence)
A damp or musty smell
Mould growing on the lower section of walls or in the corners

If you are unsure if you have rising damp you can contact a surveyor. They will inspect the property and use moisture detectors to confirm whether the property has rising damp.

How to treat rising damp

Treating rising damp involves several steps. These are:

Identifying the cause: Check for broken drainage systems and faulty DPCs. You can check your DPC type by reviewing building plans or by consulting a professional. Look for dampness where the DPC is and check for damage.

damp proof course on exterior brick wall

A traditional / physical DPC can be identified by a horizontal strip embedded into external walls, often 15cm above the ground, made from slate, bitumen, metal or plastic. The DPC should always be above the ground level. Please note that internal DPMs made of rubber and modern chemical damp proof courses will not be visible.

Improving drainage and guttering: Repair and clean blocked drainage and guttering systems. Drainage systems should direct water away from the property. You can also improve the soil grading around a building’s foundations to prevent water from pooling near the base, or install French drains around the home’s perimeter.

Installing or repairing damp proof courses: If the current DPC is damaged or non-existent, you can install a new physical DPC or inject a chemical DPC into the walls. You can also install DPMs internally.

Waterproofing and repairing foundations: Waterproofing treatments and sealants can be applied to a building’s exterior to prevent further water ingress. Cracks in the building’s foundations should be fixed as soon as possible.

Treating damp walls: Remove any damaged materials from the walls and re-plaster them using breathable and moisture-resistant materials. Let the affected areas fully dry out before re-plastering or painting.

How much does rising damp treatment cost?

As there are many steps involved and multiple causes for rising damp, fixing the issue can cost anywhere from £500 to £7,500* if you hire a professional. The price will depend on the size of the property and the extent of the water damage.)(*Price estimates calculated July 2024, using information from Checkatrade.)

How to treat rising damp in an old house DIY

If you’re on a tight budget, you could try Dryrod damp proofing rods. They are easy to install, so long as you have a masonry drill, and they effectively stop rising damp. A pack of 50 retails for £89.51* (ex. VAT), and you can save on labour costs by installing them yourself. These damp proofing rods are guaranteed to stop rising damp for up to 20 years. To see how simple this DIY is, check out Skill Builder’s ‘Easy DIY Solution to Treat Rising Damp in Walls’ video. (*This is the Builder Depot retail price, last checked on 23/07/24.)

How do dry rods work?

Dry rods for damp work by being inserted into drilled holes in the wall. The rods release a chemical that spreads to create a waterproof barrier. This barrier helps to prevent rising damp from spreading up the walls.

What is penetrating damp?

Penetrating damp, also called lateral damp, is when water enters a building through the roof or external walls. It usually occurs when the building is damaged or poorly constructed. This type of damp travels horizontally through walls, causing stained patches on internal walls.

External water sources directly contribute to penetrating dampness, so it becomes noticeably worse after heavy rainfall.

Damaged roofs: Missing roof tiles, deteriorated roof membranes and faulty flashing.
Broken pointing and masonry: Deteriorated mortar joints or cracked brickwork.
Faulty doors and windows: Poorly sealed doors and windows.
Bad building design: Architectural choices that lead water to collect.
Damaged wall coatings: Old render or cladding can make a house susceptible to water ingress.
Leaking pipes: Plumbing leaks can cause damp patches to appear, especially on ceilings and walls.
Bridging of cavity walls: Debris or mortar connecting cavity walls lets water pass from the external wall to the internal wall.

What does penetrating damp look like?

You can identify penetrating damp by looking at both the interior and exterior of a building. Penetrating damp, unlike rising damp, can appear anywhere water can enter, without being limited to a uniform height. When checking for penetrating dampness, the common signs are:

Wet patches on interior walls or ceilings
Peeling wallpaper or bubbling paint
Mildew and mould growth
Brown or yellow water stains on ceilings or walls
Blistering, crumbling or bubbling plaster
A damp and musty odour
Dark or green stains on external walls
Visible damage or cracks in the external walls
Moss or algae growing on walls
Powdery white salt deposits on brickwork (efflorescence)
Crumbling mortar joints

How to fix penetrating damp

To treat penetrating damp, you need to first identify the defects in the building’s exterior that allow the water to penetrate. The best places to check are external walls, windows, gutters, roofs, and downpipes. Look for obvious signs of damp on external walls, as well as damage or wear that would allow water to enter. With penetrating damp, the external defect is likely to be close to where the internal damp appears. Once you have identified the cause, you can:

Repair external damage: Replace missing / broken roof tiles, replace faulty flashing, clear gutter blockages, fix gutter leaks, ensure downpipes direct water away from buildings, repoint damaged mortar joints, repair masonry cracks, seal gaps around doors and windows (or replace damaged frames), repair damaged render and replace faulty cladding.
Wait for the internal damp to dry: Once the internal walls have completely dried, you can re-plaster and paint.
Treat mould growth: Treat any internal mould growth and re-paint the area with anti-mould paint. See our Preventing & Removing Mould guide for more information.
Improve insulation and ventilation: Ensure the building is well insulated and ventilated to prevent moisture build-up.
Waterproofing: Add an extra layer of moisture protection by applying a waterproof coating to external walls.

If you are struggling to identify the source of the penetrating damp, you can hire a surveyor to find the cause.

What is condensation?

Condensation occurs when warm wet air comes into contact with a cool surface, causing the moisture to condense into water droplets. This type of dampness is common in the winter, with condensation forming in homes with insufficient ventilation and insulation. It usually appears on windows and walls. The good news is it can be the easiest and most budget-friendly dampness type to fix.

What causes condensation?

Condensation is more common in homes in the colder months. This is because reduced ventilation leads to higher indoor humidity. In winter, many people keep their windows and vents shut to prevent heat loss and lower their energy bills, but this leads to condensation and mould growth. The main causes of condensation are:

High levels of indoor humidity: Cooking, showering and drying laundry indoors releases moisture into the air.
Poor ventilation: The moisture in the air becomes trapped inside the home.
Cold surfaces: Moisture condenses on surfaces cooler than the air. This is particularly true for single glazed windows at night or in the winter.
Poor insulation: Poor insulation means colder indoor surfaces, which leads to condensation.
Unvented tumble dryers: Tumble dryers that are not vented outside add moisture to the air.

How can you spot condensation damp?

Common signs of condensation are:

Visible water droplets on windows are regularly visible early in the morning.
Water droplets form on the walls and ceilings, especially in the corners of rooms with poor ventilation. These can seem like a random wet spot on the wall.
Damp patches on walls and ceilings near windows that are not caused by penetrating damp. (Condensation damp is more evenly spread than penetrating damp.)
Condensation spots on walls can cause mould and mildew growth.
A damp and musty odour.
Mould or damp on curtains and blinds.

How to stop condensation

Stopping condensation damp inside your home can involve several strategies. These include improving ventilation, decreasing humidity, lifestyle changes and upgrading insulation.

Improving ventilation: Upgrade extractor fans in the kitchen and bathroom, open windows regularly, install window trickle vents and keep passive air vents open.
Decreasing humidity: Run a dehumidifier to dry out rooms, ensure tumble dryers are vented outside, leave extractor fans on for longer after cooking and showering, and place moisture-absorbent materials into closed spaces like wardrobes.
Lifestyle changes: Dry clothes outside rather than indoors, cover pots and pans with lids while cooking, turn on cooker hoods when cooking, take shorter showers and limit the number of houseplants. (Houseplants can lead to higher humidity as they release moisture. Alternatively, if you’re a fan of plants, opt for species that absorb moisture like peace lilies or ferns.)
Upgrading insulation: Replace single glazed windows with double/triple glazed windows, install adequate insulation in walls, roofs and floors, and repair any broken window seals.

Mould condensation spots on walls should also be treated with anti-mould products. See our Preventing & Removing Mould guide page to learn more.

Telling apart the different types of damp

It can be difficult to tell different types of damp apart. Below we’ve categorised the main types of dampness and the key signs to look out for. It’s worth noting that a building may have more than one kind of damp.

Type of damp	Rising damp	Penetrating damp	Condensation damp
Key signs to look for	Horizontal lines of salt deposits on walls Damp patches on walls starting from the floor and going upwards Decayed skirting boards Damaged or non-existent DPC	Localised damp patches on the walls and ceilings Damp becomes worse after rainfall Damage and discolouration to external walls Mould growing on interior walls that correspond with external defect locations	Water droplets on cold surfaces Mould growing in corners and around windows High indoor humidity detected by a hygrometer Damp walls that are not insulated

How does poor ventilation contribute to damp?

Poor ventilation exacerbates the problems of dampness, especially condensation damp. Without sufficient ventilation, moisture in the air becomes trapped in buildings, leaving them damp (when condensation occurs) and unable to dry out. Continually damp surfaces provide ideal conditions for mould growth, which poses a health risk. Therefore, having adequate ventilation is important to prevent dampness and maintain a healthy living environment.

How can landscaping help prevent damp?

Landscaping and exterior drainage are important to prevent dampness inside homes. By landscaping, you can manage water flow and direct drainage away from properties. This is important for preventing rising damp. To prevent dampness via landscaping, you may wish to consider:

Ground sloping / grading: Make sure the ground around your property slopes away from the building’s foundations. This will direct water away from the house, helping to reduce the effects of rising damp.
Installing drainage systems: French drains, swales and surface drains will channel water away from your home.
Upgrading downspouts: Extend downspouts further away from your house and install a downspout extender.
Strategic planting: Plant native plants, trees and shrubs that absorb groundwater and require little water themselves near your property.
Managing water features: Build ponds, fountains, and other water features away from the building’s foundations. Remember to properly line them to prevent leaks.

How to assess the extent of dampness in your home

To find out the extent of the damp, you can conduct a visual inspection or use diagnostic tools. Assessing the extent of dampness in your home helps work out how severe any building damage is. This can inform how much repairs may cost. Finding the source of damp and fixing it as soon as possible is pertinent for keeping repair costs down. The more issues contributing to the dampness, and the more water found, the worse it is.

When performing a visual inspection, check for:

Discolouration and water stains on the walls and ceilings
Wet patches on internal walls
Warped flooring
Condensation on windows
Mould growth or peeling paint around windows
Damp around sinks, showers, baths and underneath cabinets
Mould, mildew and musty smells in basements and attics
Damage, efflorescence, and cracks in external brickwork
Missing or broken roof tiles
Blocked / damaged gutters and downpipes
Plumbing leaks
Broken seals and caulking

A hygrometer can come in handy if you wish to use diagnostic tools. Hydrometers measure indoor humidity levels, which should be between 30% and 50%. Some modern thermostats have in-built hygrometers, so it’s worth checking if your thermostat has a humidity reader before you rush out to buy a new tool. If in doubt, hire a damp specialist or surveyor to inspect your property and give you a detailed report on your damp problem

DIYs to address minor damp

If the dampness in your home isn’t major, a simple DIY job could fix it. You could try:

Improving ventilation by opening windows, using kitchen and bathroom fans, and installing air ventilation grills.
Using a dehumidifier to control humidity levels.
Fixing plumbing leaks as soon as you find them. You could try PTFE tape for a straightforward DIY, or replacing damaged plumbing parts.
Sealing gaps around windows and doors to prevent water ingress.
Resealing joins around sinks and baths with a mould-resistant sealant.
Upgrading insulation in the roof and around pipework. You can use pipe insulation to prevent condensation from forming on them. Larger insulation jobs may require a professional.
Applying anti-condensation paint in damp-prone areas. This can include bathrooms, kitchens and around windows.
Extending downspouts by using a downspout extender.
Using anti-mould products to treat and prevent mould growth.
Installing Dryrod damp proofing rods to stop rising damp.

These quick DIYs can help you manage the dampness inside your home. However, it’s worth hiring a professional builder for jobs like installing a new DPC, re-plastering, or more complex tasks.

What professional services are available to treat dampness?

If your property has a severe damp problem that DIY jobs cannot fix, there are professional services that can help. In the UK, some specialists deal with treating dampness, and they usually offer an in-depth building assessment along with tailored damp solutions. Some key services available are:

Damp proofing specialists: They inspect and inform you on the extent of your damp, install and repair damp proof courses, inject chemical damp proofing into walls, and apply waterproof membranes and tanking slurry to floors and walls.
Ventilation experts: They install new ventilation systems (or upgrade existing ones) to help reduce humidity and indoor air pollution.
Building surveyors: They conduct thorough building inspections to identify damp and structural issues within the building, use moisture meters and thermal imaging to map the areas of dampness, and provide recommendations to remedy the situation.
Mould removal services: They identify the sources of mould, safely remove mould growth and help implement mould prevention measures.
Roofing services: Roofers can repair damaged roofs to stop water ingress.
Gutter maintenance services: They clean and repair gutters and downpipes to ensure proper drainage. This can solve penetrating damp.
Timber rot specialists: They treat timber for dry rot, wet rot, woodworm and more, which can occur because of damp. These specialists can also identify weakened timber beams and perform structural repairs.
Remember when choosing a professional service to: check their qualifications / certifications, read reviews, ask about their guarantees, see if they have experience dealing with similar issues to the ones in your property, and get quotes from multiple companies to see if you’re getting a fair deal. By doing so, you can effectively address the damp in your home without overpaying.

Common misconceptions about damp

Common misconceptions about dampness can make the issue worse, leading to more structural damage and expensive repair costs. The most common damp myths include:

Damp is a winter problem: Whilst condensation damp is more likely to happen in the winter, it can occur all year round.
Painting over damp will fix it: Painting over damp only masks the underlying issue.
Condensation damp isn’t serious: Prolonged condensation leads to mould growth, which can cause structural issues within the building and health risks.
Damp will dry out on its own: Without fixing the cause of the dampness, it will only get worse and not dry out.
Only old buildings get damp: Old buildings can be more susceptible to dampness, but new builds can experience damp because of poor construction, condensation and water leaks.
Damp proof courses last forever: Damp proof courses can deteriorate over time and maintenance may be required. The average damp proof course has a lifespan of 25 years.
Damp is always visible: Some damp problems, like those in walls and floors, may not be immediately visible.

FAQs

How many types of damp are there?

There are three main types of dampness: condensation, penetrating damp and rising damp.

Why is my house so damp?

Your house may be damp because of high indoor humidity, insufficient ventilation, water leaks, roof leaks and rising damp. It’s best to identify the source of dampness as quickly as possible to treat it effectively.

Why are there little brown spots on my walls?

Small brown spots on walls may indicate damp issues like mould or water damage. The spots are often caused by water seeping through the wall causing discolouration.

What causes condensation on windows?

Condensation forms on windows as moisture in the air condenses onto the cold window surface to form water droplets. This commonly happens in humid environments and single glazed windows.

How to stop condensation on windows overnight

To prevent condensation from forming on windows overnight, try improving ventilation by slightly opening the window or using a ventilation fan. Alternatively, you could try a dehumidifier to reduce indoor humidity levels.

How to remove condensation from windows

Remove condensation from windows by wiping the glass with a clean dry cloth to soak up the moisture. If possible, improve the ventilation by opening the window or using an exhaust fan.

How to get rid of condensation inside double glazed windows

If condensation forms between the two glass panels of a double glazed window, it typically indicates the window seal is broken. This means you will need to replace the window or the window seal. In the meantime, you can use a dehumidifier to reduce indoor humidity so condensation is less likely to form.

How to stop condensation on toilet cistern

To prevent condensation forming on toilet cisterns, try insulating the cistern with a thermal wrap, or install an insulated tank. You can also decrease bathroom humidity by turning on the extractor fans, using a dehumidifier, and taking shorter showers.

How to dry out condensation in a loft

To dry out condensation in a loft you must first fix the cause of the dampness. This may require fixing roof leaks, installing a vapour barrier, or upgrading your loft insulation. You can then enhance ventilation by installing air vents or an electric ventilation system. It may also help to use a dehumidifier.

What does damp mean?

Damp refers to unwanted moisture in a building that causes mould, structural damage and poses a health risk.

What does damp look like?

Damp appears as discoloured patches on the walls and it causes a musty smell. Prolonged dampness also causes paint and wallpaper to peel and mould to grow. You may also see crumbling plaster and rotting timber.

Types of Damp and Tips To Tackle It