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How to deal with damp

  • 16, Aug 2020
  • Read time: 10 mins

This guide will help you understand what damp is, how to identify it, what measures you can use to remove it, plus how you can prevent damp from happening in the future.

Damp on walls.

What is damp?

Damp is excessive moisture within the structure of your home that can cause multiple problems if not resolved as soon as possible.

It’s recognisable as a concentrated patch of moisture or unsightly discolouration, usually accompanied by a musty smell.

Ignoring damp is not a good idea. It damages walls, windows frames and anyone living in a house with damp could develop health or respiratory problems.

It is also not covered by many buildings insurance policies as damp is a gradually occurring issue and would fall within the ‘maintenance and wear and tear’ exclusion.

There are three types of damp; rising damp, penetrating damp and condensation. Let’s take a look at them in order.

What is rising damp?

Rising damp is moisture coming up from the ground and rising through the structure of your home.

It is noticeable on the lower parts of walls to a height of about a metre and also across solid concrete floors. Wet weather makes rising damp worse as walls have more water to soak up.

Modern houses are usually constructed with a damp-proof membrane acting as a waterproof barrier under concrete flooring.

In the walls this is referred to as a ‘damp-proof course’. Your building may not have either of these, depending on its age, or your damp-proofing could simply be damaged, leading to instances of damp.

What are the signs of rising damp?

  • Appearance of damp stains and patches on walls
  • Ironwork shows signs of rust
  • Loose or rotting flooring or skirting
  • Crumbling or flaky or salt-encrusted plaster-work

How to fix rising damp?

Calling a professional to fit or replace a damp-proof course or membrane is one action you could take. If there are just a few wet patches on the floor, then it might be that the membrane itself is only slightly damaged, in which case painting the floor with a waterproof emulsion might help here.

The damp-proof course in the walls should be at a height of 15cm. If you spot any wet patches above this height on an exterior wall, check that there’s nothing on the other side that is responsible for the moisture, such as a raised path or piles of damp earth.

What is penetrating damp?

While rising damp relates specifically to moisture from the ground, penetrating damp can come from anywhere. It might lead to wet patches on the ceiling or towards the top of a wall, which can signal a leak somewhere, or the bricks themselves may be so old that they have become porous, allowing entire walls to soak up water like a sponge.

What are the signs of penetrating damp?

  • Drips or puddles.
  • Peeling wallpaper
  • Crumbling plasterwork
  • Patches that turn dark during rain
  • Increasing damp circles on walls, floors and ceilings

How to fix penetrating damp?

Finding the source and fixing it should hopefully make the problem go away. Check that there are no leaking pipes, that guttering is not broken or blocked, there are no missing or damaged roof tiles, and that any joints are properly sealed.

If damp on walls is caused because of damaged or porous bricks on the outside of the building, it might be that they need replacing. You can try filling in any gaps in the mortar and also treat the bricks with a water-repellent product as another way of damp-proofing walls.

Other areas to check might be around the door and window frames. There could be gaps that need filling with sealant, or rotten wood that needs replacing.

What is condensation?

In a home with no real structural problems, condensation might be the most likely cause of damp. Warmth causes moisture to evaporate into the air, and as soon as it hits a cold surface turns back into liquid, covering the wall or window with water droplets. This moisture can sometimes soak into the window frames (making them rot) or into the walls.

What are the signs of condensation?

  • Water found on windows or walls.
  • Rotting and stained window frames
  • Peeling wallpaper
  • Musty smell
  • Spread of mould on fabrics from carpets to curtains

How to fix condensation

The solution here is perhaps the simplest form of damp proofing – opening windows to allow the moist air to escape easily. Double glazing and insulation can not only stop heat being lost in the house, but also make sure that walls and window panes don’t get quite as cold (and create condensation). You can also try using a dehumidifier.

Also check that there are no areas where condensation might build up unnoticed. A sealed fireplace or chimney will still have a flue running behind it, and the moist air will need to circulate.

Make sure a vent is fitted to prevent a build-up. Similarly, in a loft or basement, check that vents or airbricks are allowing circulation to take place.

Ignoring condensation can lead to problems and some of these issues might not covered by your insurance.

What causes damp?

Damp is the presence of higher levels of moisture in the structure of a building. It can be caused by:

  • Faulty pipes, guttering or drainage
  • High levels of ground around the property
  • Vents and airbricks blocked
  • Rising damp from cellars
  • Rainwater through roof or windows

The signs of damp in a house

You may smell damp before your spot tell-tale signs of damp, but these are some of the things to look out for:

  • Stains or patches of mould on walls
  • A musty smell
  • Excessive condensation on windows
  • Peeling wallpaper
  • Paint blisters
  • Crumbling plasterwork

Signs of rising damp in a house 

Rising damp is caused by moisture in the ground rising through the structure of a building. The common signs of rising damp are:

  • Salty deposits on plaster work
  • Rotting floorboards or skirting
  • Decaying mortar between bricks
  • Corroding ironwork
  • Flaking paint

Damp on the outside walls

Damp can start in many places but can also be created by external factors. These include water leaks from damaged roofing, flashing or where gutters have been blocked by tree debris. Another factor is crumbling masonry, render or mortar.

Old brickwork can deteriorate over time, becoming absorbent rather than resistant, while cracks can make problems worse.

Overgrown foliage or even rubbish that has not been cleared in a long while can cause damp to spread through external walls.

How to fix damp walls

Regularly inspect your property to ensure trees and bushes aren’t disturbing the masonry in anyway. Check roofing and guttering to ensure water flow is correct. Don’t allow a simple maintenance issue to increase until it’s having a detrimental effect on your home. Carrying out regular checks and maintenance could save you an expensive bill in the future.

How to prevent damp

Preventing damp entails a combination of regular maintenance checks which include tasks that can be concluded without calling in professionals. These include:

  • Ensuring rooms are well ventilated
  • Clear any debris around the property
  • Making regular checks to roofing
  • Make sure all vents are clear particularly in the kitchen and bathrooms
  • Make sure kitchens are properly ventilated when cooking
  • Air your home
  • Use a dehumidifier to extract moisture

What is mould?

Mould is fungi. Look closely and you’ll see it grows outwards in green or black filaments. Mould grows on food and is a danger to health, especially for those with asthma or other respiratory conditions. It can cause allergic reactions such as stinging eyes, nose, throat or lungs.

What is mildew?

Mildew is fungi and is usually grey in colour. Look closely and you’ll see a flat or thin layer of filaments. Mildew can be found on damp surfaces from bathrooms to cellars, carpets and curtains and it smells musty. It can grow on most surfaces and is hazardous to health, either by touch or inhalation.

    How to remove mould and mildew from walls

    Natural solutions include the use of vinegar, distilled in a bottle and sprayed onto the surface. Then leave for an hour, before returning to scrub the mould or mildew off. This should work for smaller surface areas. If the problem is more widespread then consult a trusted tradesperson for large scale solutions.

    How to prevent mould from returning

    Once you’ve taken the effort of getting rid of mould, here are six ways to stop it from returning.

    1. Wash and disinfect surfaces that suffer from mould
    2. Fix internal or external causes of leaks
    3. Maintain ventilation and open windows
    4. Clear any rubbish and debris
    5. Use a dehumidifier and clean extractor fans
    6. Clean and dry carpets

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