How to deal with damp, mould and condensation

We get a lot of calls during the colder months with tenants saying they’ve got mould starting to appear in their property and “can the landlord fix it please”. There’s not usually any signs of it in the summer, it just starts in the colder months.

Unfortunately in the large majority of cases, there’s really not a lot the landlord can do about it as it’s a combination of factors that are usually outside of their control (this of course unless there is damp caused by leaks, poor loft insulation, poor damp course etc).

Therefore there are several simple things a tenant needs to do to keep damp and mould under control.

The basic causes of damp & mould

Damp & mould are primarily caused when there’s a condensation build up in a particular part of a property. Condensation is simply warm humid air hitting a colder surface and turning back into water droplets. The buildup of moisture/damp overtime in a warm environment, is an ideal breeding ground for mould.

Mould generally grows closer to bathrooms and kitchens, in corners and on the walls of rooms with external walls and behind furniture that’s close to the wall prevent air flow.

Poor ventilation is also a major contributing factor to condensation and should be taken into account when trying to reduce it.

What causes condensation?

Condensation forms if the air inside the property is humid (warm air with lots of water vapour in it) and it hits a surface below a certain temperature.

Condensation needs a cold surface to “condensate” on which is why this tends to happen more in the colder months. External walls and windows (even if double glazed) are colder than the warm air generated by the heating, hence why you get more condensation in the autumn/winter. You also tend to have windows and doors closed in the colder months which traps warm humid air inside the property.

Walls and windows will always be colder than the warm air in a heated property on a cold day. Wall construction and whether the windows are double glazed or not play a factor in this of course. Single glazed windows units are significantly more susceptible, and landlords should consider replacing them if possible.

Cavity wall insulation is a big topic of debate within the industry. On one side you have those that say “the insulation keeps the internal wall warmer” but on the other side you have those that say “as with double glazing, once you remove the air gap between the bricks, you are creating a medium for mould and damp to travel through”. In general, if you have cavity walls, you’re fine whether it’s insulated or not.

To keep the walls from getting too cold and your pipes from freezing, during the colder months you should set your heating to go no lower than 15 degrees (this is actually a condition in a lot of insurance policies too). Most modern thermostats let you set a minimum temperature, if you have an older thermostat, just set the heating to be permanently on but set the thermostat to be around 15 degrees when you’re not in. This will keep the walls from becoming too cold.

Ventilation is also very important during winter months especially in bathrooms and kitchens. Trickle vents on windows should always be open and if you’re doing a lot of cooking or taking a shower, ensure the extractor fans are on and if not, open the windows slightly.

You obviously need the air to be warm in your property so you can’t do anything about that apart from not having your heating set too high, usually 22-23 degrees is considered normal.

How to control humidity

Humidity is by far the biggest contributor to condensation. Humidity is basically warm air with lots of water vapour in it, here’s a few examples of things that contribute to high humidity: –

  • Drying clothes on a radiator
  • Boiling water in the kitchen, cooking, kettle, etc
  • Taking a shower
  • Running a bath
  • Breathing!

As you can see, a lot of these are unavoidable (especially breathing!) so what can you do about it?

  • Always cook with pan lids on and turn the heat down once the water has boiled
  • Only use the minimum amount of water for cooking vegetables
  • When filling the bath, run the cold water first then add the hot – it will reduce the steam which leads to condensation by up to 90%
  • Never dry laundry on radiators
  • Dry washing outdoors if possible, or put it in the bathroom with the door closed and the window open or extractor fan on
  • Extractor Fans should be automatically humidistat controlled or timed – not solely activated by a light switch
  • If you use a tumble dryer, make sure it is vented to the outside (DIY kits are available for this) or that the tumble dryer is of the new condensing type
  • Don’t use your gas cooker to heat your kitchen as it produces moisture when burning gas (you will notice the windows misting up)
  • Never use bottled gas heaters (Calor etc.) as they produce about 8 pints of moisture from an average-sized gas bottle

How to improve ventilation

Some ventilation is needed to get rid of the moisture being produced at the time, including that from people’s breathing. Keep trickle vents open at all times, alternatively open small window/top lights.

  • Use passive Vapour Vents if no trickle vents are fitted to windows
  • Do not have airbricks fitted at low levels
  • Kitchen and bathrooms require more ventilation due to cooking, washing, bathing and drying creating high levels of moisture which means opening windows
  • Ideally these rooms should be fitted with humidistat controlled extractor fans (these work automatically when humid air is detected
  • Close the bathroom and kitchen doors when these rooms are in use, even if the kitchen or bathroom has extractor fans (this stops the moisture reaching other rooms, especially bedrooms which are often colder and more vulnerable for condensation)
  • Allow space for the air to circulate in and around your furniture
  • Open doors to ventilate cupboards and wardrobes
  • Leave space between the backs of wardrobes and the wall
  • Where possible, position wardrobes and furniture against internal walls i.e. walls which have a room on both sides rather than external walls
  • To reduce the risk of mildew on clothes and other stored items, allow air to circulate round them by removing ‘false’ wardrobe backs or drilling breather holes in them
  • You can place furniture on blocks to allow air to circulate beneath
  • Never overfill wardrobes and cupboards as it restricts air circulation

Cleaning mould

Surface mould created in these situatons can be easily cleaned by using a supermarket anti-mould spray. If the mould has gotten behind the paintwork etc, the landlord may need to get the wall treated and repainted.


Kent Council – How to prevent damp, mould and condensation in your home

Condensation in your property – A guide to the causes and how to remedy the problem

AXA – What causes condensation and how to stop it


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