How to get rid of damp and mould

9th July 2019

Damp and mould isn’t only unsightly, it can affect your health too, so it’s important to treat it as soon as you can. It’s all caused by excess moisture but there are three main types of damp in homes and they are treated differently. First, you need to identify which type you have and it’s likely to be one of the following: condensation; rising damp or penetrating damp.


What is it? This most common form of damp is caused when moist, warm air condenses on cool walls, windowsills and mirrors. It’s mainly a winter problem as the walls tend to be cooler than the air inside. It appears as dark mould, can have an unpleasant smell, and if left untreated can damage paint and plaster and cause window frames to decay.

What causes it? It’s caused by the warm, moist air from cooking, showering and drying clothes indoors. Renovations to older houses, like removing ‘breathable’ old chimneys and fitting air-tight double glazing can reduce ventilation and lead to damp problems.

How can I prevent it? You can help prevent the build-up of condensation by:

  • Putting lids on saucepans, drying washing outside and avoiding using paraffin or bottled gas heaters
  • Opening the bedroom window for 15 minutes each morning
  • Making sure your home is well insulated
  • Keeping your home heated at a steady/regular temperature rather than allowing your home to get cold and then turning the heating up – a minimum of 10oC for an unused room and 16oC for used room
  • Ventilating rooms, especially bedrooms daily and leaving doors open to allow air to circulate when possible
  • Not having furniture too close to an external wall
  • If you’re cooking opening the window, putting the fan on and closing the door
  • When showering/bathing using the extractor fan, if there is one, and opening the window for 15-20 minutes after you have finished showering/bathing, along with keeping the bathroom door shut
  • Not having the windows open too long in cold weather – cold walls attract moisture and can make the problem worse

How to treat it Repairs may be needed to get rid of any leaks or to improve ventilation. Options include:

  • Installing extractor fans in the bathroom and kitchen
  • Installing dehumidifiers in affected rooms
  • Building air bricks into outside walls
  • Installing air vents through internal walls or sealed chimneys to allow air to circulate
  • Adding window vents to the top of window frames
  • Fitting roof ventilation tiles and/or ventilated soffits to allow air through the loft
  • After such repairs, or if the home is damp because it’s newly built, it may take weeks of heating and ventilating it to dry it out.
  • Removing mould

Once you’ve identified and fixed the source of moisture in your home you can get rid of any mould. You may be able to remove it yourself or get professional help.

NHS Direct advises that you only remove mould yourself if it’s caused by condensation and covers an area less than 1 metre squared (1×1 metre or 3×3 feet). Don’t try to remove the mould yourself if it’s caused by sewage or other contaminated water.

Protect yourself from mould spores by wearing goggles, long rubber gloves and a mask that covers your nose and mouth. Open the windows but keep doors closed to prevent spores spreading to other areas of the house.

Remove any mouldy soft furnishings, clothes and soft toys in a plastic bag. Soft furnishings should be shampooed and clothes professionally dry cleaned

  • Fill a bucket with water and some mild detergent, such as washing-up liquid or a soap used for hand-washing clothes
  • Use a rag dipped in the soapy water to carefully wipe the mould off the wall. Be careful not to brush it, as this can release mould spores
  • When you’ve finished, use a dry rag to remove the moisture from the wall
  • Afterwards, put the rags in a plastic bag and throw them away
  • All the surfaces in the room should be thoroughly cleaned by either wet wiping or vacuuming to remove any spores

Rising Damp

What is it? This is caused by ground water moving up through a wall or floor. It might cause paint or wallpaper to peel, or a white fluffy salt powder to appear on the wall. Yellow or brown tide marks can rise up the wall, skirting boards or plaster can decay, or floor coverings may lift up.

What causes it? If the building was built before 1875, it might not have damp-proof course or membrane, or they might have been damaged over time. (Your damp-proof course should be visible outside the property, as a waterproof horizontal strip 15-16cm above the ground). Rising damp happens then there’s a lack of drainage, if the ground outside the property is higher than the damp-proof course, or if an outside structure such as steps is allowing water to get in above it.

How to treat it Install a damp-proof course or lay a damp-proof membrane underneath the floor, connected to the damp-proof course, to seal off the house from ground water.

Penetrating Damp

What is it? It’s caused by water leaking through walls, or sometimes ceilings, travelling horizontally rather than vertically, like rising damp. You’ll see damp patches, which may worsen when it rains.

What causes it?  Rain seeping in through cracks in external walls, a damaged roof, guttering, windowsill or door surround, or leaking internal or external pipes.

How to treat it Look out for damp patches and discolouration on external and internal walls. Check your guttering and downpipes for leaks and/or blockages, as they are a common cause of penetrating damp. If an old brick has become porous a builder can usually replace the brick. Another potential cause is a cavity wall problem. We suggest you get advice from a builder, in case it’s a structural issue.

At Letters we take our duty of care to both tenants and landlords very seriously. We’re happy to give advice and recommend our trusted tradesmen to help you tackle damp or any other problems associated with your property. Please contact us to have a chat. If you’re a tenant in a property managed by us, our repair reporting system also gives advice on preventing and treating condensation/mould.