How you can identify condensation, mould and damp, how they can be treated, and what you can do to prevent them.


There is always some moisture in the air inside your home.

Everyday activities, especially cooking, washing, bathing, and even breathing are the main causes of this moisture. Condensation is an effect of this moisture in the air. When this air becomes cold, the moisture condenses to form water droplets, or condensation. This is most noticeable on windows in the morning. It appears on cold surfaces and in places where there is little air movement, so you should regularly check in corners, on or around windows and behind wardrobes and cupboards for signs of condensation.

Condensation can cause black mould on walls, clothes, and furniture. This may look unpleasant and have a musty smell. In some cases, condensation can even affect plasterwork and rot wooden window frames. Despite being far more common than damp, condensation is often confused with damp.

How to treat and prevent condensation

Condensation can be treated or prevented by increasing insulation and draft-proofing, and efficiently heating your home. Insulation and draught proofing will help keep your home warm and cut fuel bills. When the whole home is warmer, condensation is less likely. In cold weather, ensure that the property is well heated (warm air will not hold moisture as well as cold air can). This can be achieved by ensuring that heating is left on a low setting all-day.

We appreciate that heating your home can be costly and that keeping heating on when you are out could appear wasteful, but if it is at a low level, the boiler will not have to work as hard to reheat the home, making this method more efficient and economical.

You can also avoid condensation by producing less moisture. Always cook with lids on pans, using the minimum amount of water possible, turning the heat down once the water has boiled. Cover pans when cooking and do not leave kettles boiling. When using a bath, fill with cold water and then hot, avoiding excessive steam.

Do not use paraffin or calor gas heaters as these put a lot of moisture the air. It is stated within most tenancy agreements that you are not allowed to use oil, paraffin, or bottled gas heaters in your home.

Dry washing outdoors on a line or in the bathroom, with the door closed and a window open or an extractor fan running.

Vent tumble dryers directly to the external of the building. Use extractor fans where you have them. Keep a small window ajar, or trickle ventilators open when someone is in the room.

Ventilate kitchens and bathrooms when in use by opening windows.

Ventilate cupboards and wardrobes and avoid filling them too much, as this prevents air circulating. Slatted shelves and/or breather holes in cupboards and wardrobes may help. Leaving a space between wardrobes also increases ventilation.

If windows are replaced, we will ensure that they incorporate trickle ventilators as appropriate.

How to treat and prevent mould

Mould can be treated very easily. To kill and remove mould:

  • Wipe down walls and window frames with a fungicidal wash, following the instructions precisely. These are available from most supermarkets and hardware stores
  • Dry-clean mildewed clothes and shampoo carpets
  • Do not use a vacuum cleaner or brush, this can release spores, which may make the issue worse and can increase the risk of respiratory illness
  • For any redecoration after treatment, fungicidal resistant paint and wallpaper paste should be used
  • Dry windows, windowsills and all surfaces wet by condensation each morning (especially in the kitchen and bathroom)
  • Wring out the cloths used for this, do not dry them on a radiator or heater
  • Do not block or cover vents, airbricks, chimneys, grills or permanent wall ventilators. Blocking these will decrease airflow and increase the risk of condensation
  • Do not draught proof rooms where condensation or mould is present, or where there is a cooker or fuel-burning heater
  • Do not draught proof windows in the bathroom or kitchen.

Types of damp

The term ‘damp’ refers to structural damp. This is any type of unwanted moisture that appears in the structure of you home. Structural damp is usually caused by one of the following:

Penetrating damp is caused by rain that gets through holes in a roof, spills from a blocked gutter, penetrates around a door or window frame, or leaks through a cracked pipe. It can be identified by discolouration of internal walls or ceilings, the presence of tidemarks or salt deposits.

It can also be identified by blown or blistered plaster (which will sound hollow when gently tapped) and rusted nails in skirting boards and floor timbers. Random damp patches to the walls and ceilings (at any height) may appear, and severe black mould on internal walls and window frames may be present. In general, black mould is most likely to signify condensation.

Rising damp is relatively rare. The bricks used to build houses are porous, and this means they will ‘wick’ water from the ground level and carry it up the brickwork, transferring moisture from moist bricks to dry ones. Damp courses will usually stop rising damp. Any item leaning against the wall (e.g. Rubbish, bulk items such as mattresses or soil) can allow moisture to reach brickwork above the damp course level. Where rising damp appears, and no items are leaning against a wall, it may indicate that the damp course is faulty.

This can usually be identified by damp, or wet patches on the brickwork of external walls, significant moss/lichen growth on external brickwork, and staining. Rising damp can also appear on internal walls of your home, identified by moisture and salt bands on internal walls.

How to treat and prevent damp

Water penetration should be treated by locating the root cause, or location of water penetration (e.g. a loose or cracked roof tile, or crack around a window) and undertaking maintenance repairs to the affected section. Once the repair is complete, damp areas should dry naturally. A surveyor should assess rising damp. They will determine the extent of works that need to take place. This may include replastering internal walls where plaster is salt contaminated, rendering and waterproofing and renewing the damp course, treatment may include increasing draining. You should ensure that there are no items leaning against any external wall, including soil, rubbish, mattresses, wood and temporary structures.

Contact L&Q

Visit our report a repair section to tell us about issues relating to condesation, damp and mould.