Damp is a persistent issue that can affect any home, whether modern or old. If left untreated, damp can cause structural damage, lead to health problems, and even make your home feel uncomfortable. Understanding the different types of damp is crucial to identifying the problem early and knowing how to treat it. The three main types of damp are condensation damp, rising damp, and penetrating damp. Each comes with unique causes and symptoms, requiring specific treatments. Let’s dive deeper into what these types of damp are and how to address them effectively.
1. Condensation Damp: The Most Common Type
What is Condensation Damp?
Condensation occurs when warm, moist air meets a cooler surface, such as a wall or window, causing the moisture in the air to condense into water droplets. This type of damp is more common in homes during colder months when we tend to keep windows shut and crank up the heating. Condensation is most easily recognised, it can facilitate black mould growth, which often forms black patches on the back of furniture, in corners of rooms, on ceilings, and around windows.
Key Causes of Condensation:
- Poor ventilation, especially in areas like bathrooms and kitchens.
- Activities such as drying clothes indoors or cooking without proper ventilation.
- High humidity levels indoors without enough air flow to balance it out.
- Cold walls that don’t allow for moisture to evaporate.
Treatment Tips for Condensation:
- Improve ventilation to maintain healthy moisture levels in your home by:
- Installing a Positive Input Ventilation unit. (Read our blog on PIV units.)
- Installing extractor fans in moisture-prone areas.
- Using a dehumidifier unit. (Read our blog on dehumidifiers.)
- Insulate your home to prevent cold spots that encourage condensation.
2. Rising Damp: When Moisture Comes Up from the Ground
What is Rising Damp?
Rising damp happens when groundwater moves up through the walls and floors of a building. This usually occurs in older homes with an inadequate damp-proof course and can usually be found on walls from ground level up to about 1.5 meters high. Signs of rising damp include salt crystals forming (often behind wallpaper – feels crunchy when pressed), tide marks or damp patches on walls, peeling paint, and decaying skirting and floorboards.
Key Causes of Rising Damp:
- Missing or damaged damp-proof course (DPC) in the walls.
- Damaged or missing waterproof membranes beneath floors.
- Natural capillary action drawing moisture from the ground into porous building materials such as brick or stone.
Treatment Tips for Rising Damp:
- Install or repair the damp-proof course in the walls to prevent the rise of damp.
- Use chemical damp-proofing treatments that create a water-resistant barrier in affected areas. (Read our blog on how DPC Injection.)
- Consider replacing damaged skirting boards, floorboards and plaster if necessary.
- Install a cavity drain membrane system to create a permanent waterproof barrier between the damp walls and the internal plasterwork. (Read our blog on how to install a cavity drain membrane system.)
3. Penetrating Damp: Water Seeping Through Your Walls
What is Penetrating Damp?
Penetrating damp occurs when water enters a building through external walls, roofs, or ceilings. This can be the result of damaged roofs, broken gutters, or cracks in the external structure of your home. Unlike rising damp, penetrating damp can affect any part of a building and occur at any height and is often spotted as wet patches on walls or ceilings, especially after heavy rain.
Key Causes of Penetrating Damp:
- Broken roof tiles or damaged flashing.
- Leaky gutters or downpipes that allow water to seep into walls.
- Cracked or porous brickwork allowing rainwater to penetrate.
- Defective pointing.
Treatment Tips for Penetrating Damp:
- Repair any defective roofing or gutters to prevent further water ingress.
- Repair damaged brickwork and render on external walls.
- Re-point defective areas of pointing (pointing is the surface of the mortar between the bricks).
- Check for internal plumbing leaks which can cause moisture buildup inside your home.
- Apply a water repellent coating to the external walls to stop water penetration but still allows the walls to breathe and let any trapped damp/moisture out.
General Damp Prevention Tips:
Prevention of damp is always better than dealing with the consequences of damp. By following these simple steps, you can reduce the risk of damp appearing in your home:
- Ensure your home is well-ventilated, particularly in rooms where moisture builds up like kitchens and bathrooms.
- Leave windows slightly open to encourage airflow (if possible). If this is not possible ensure that you have other means to combat humidity / increase airflow such as extractor fans, dehumidifiers and PIV units.
- Regularly inspect and maintain your roof, gutters, and external walls to prevent water ingress.
- Address plumbing issues quickly to avoid internal leaks.
Can I Fix Damp Myself or Do I Need to Seek Professional Help from a Damp Specialist?
While condensation damp can often be tackled with DIY methods like increasing ventilation, rising damp and penetrating damp may require a professional Damp Specialist (dependant on your own technical experience and capabilities). Whether you are undertaking the damp treatments yourself or using a Damp Specialist it’s important to remember that if left untreated, these forms of damp can lead to serious structural issues as well as potential health issues, so it’s best to act quickly.
By understanding the types of damp, their causes, and how to treat them, you can keep your home dry, healthy, and free from black mould which is hazardous to health. Addressing damp issues early is key to preventing costly damage and ensuring a comfortable living environment for you and your family.
Article by Mike Davison CSSW, M.Inst.SSE.
Mike has over 30 years’ experience in the construction industry & specialises in Building Pathology, remedial works & structural repair.
