Tudor Chartered Surveyors are often asked to investigate 'damp' and 'black mould' issues in properties. Black mould is, more often than not, associated with condensation. 

Condensation is the most common form of damp in properties and, if allowed to continue untreated, it will deteriorate the fabric of the building and will have a detrimental effect on the occupier's health. For these reasons we consider all reported issues with importance and urgency.

If your property is suffering from condensation, you are not alone. One in five homes across the UK suffer from condensation and in winter months when the temperature drops the issue will be more noticeable and your problems with condensation could get worse unless steps are taken.

It occurs when excess moisture in the air comes into contact with a cold surface, such as a window or a cold wall. It can lead to mould growth and tends to be worse in winter.

What exactly is Condensation?

There is always moisture in the air, even if you can't see it. Warm air can hold more moisture and as the air gets colder its ability to hold the moisture reduces, resulting in small droplets of water appearing, particularly on colder surfaces. This is condensation

You will see this in action when you breath out on a cold day, when the mirror mists over when you have a bath or just like moisture condenses on a cold beer on a hot summer day!

The point at which air cooled down enough for condensation to occur is called dew point and this is the point that air cannot absorb enough vapour anymore and the vapours then begin to condense on cold surfaces.

In the cold months the window glass is often colder than the dew point, so moisture would condense on it easily. This will also happen on colder walls and corners or unventilated spaces such as behind furniture. It is often found on north-facing walls being the colder wall of any building.

In most cases the moisture in the air is produced by normal everyday living, from boiling kettles to running a bath. Kitchens and bathrooms are often the primary sources of moisture in the air but this moisture will migrate from high moisture areas in the dwelling to lower moisture areas. 

condensationMould1Black Mould

Condensation can lead to staining and mould growth, damaging wallpaper, wall surfaces, window frames, furniture and clothes (even inside a free-standing wardrobe).

Mould growth is the most tell-tale sign associated with condensation. This mould is usually black in colour but can be white, yellow or green. Black spot mould (Asperigillus nigeror Cladospoium) will form pyramid profiles in wall corners and at wall/floor or wall/ceiling junctions and is as a consequence of condensation.

Moulds are fungi that require high level of surface moisture to allow growth and germination. Penetrating and rising damp do not offer sufficient moisture for mould growth.  

The mould will produces small spores which can increase the risk of asthma and respiratory illnesses in some people.

Maintaining a reasonable balance between heating, ventilation and insulation can reduce the excessive condensation however, on occasions a review of lifestyle and occupation of the dwelling is often necessary.

In the short-term consider all sources of moisture and reduce those if possible. Please wipe off condensed water from windows and sills every morning and wring out the cloth into a sink rather than drying it on a radiator!

Cleaning Mould

Regular cleaning away of mould is very important.

To remove the mould, wipe down the affected area with a weak bleach cloth or a preparatory mouldicide or fungicidal wash, always follow the manufacturer's instructions. Spray containers can be obtained from retailers and mould kits can be obtained from specialist suppliers. 

Dry-clean mildewed clothes and shampoo carpets. Disturbing the mould by brushing or vacuum-cleaning can increase the risk of distribution of spores which can cause respiratory problems. Redecorating with fungicidal paint will help prevent mould reoccurring provided that condensation can be eliminated (or reduced) at the same time. 

A dehumidifier can help to reduce airborne moisture which will in turn reduce condensation, however, it will not solve the source of the moisture. 

How to Avoid Condensation - and Mould 

Produce less moisture - Reduce the potential for condensation by producing less moisture

It can help if you:

  • cover pans when cooking and turn the heat down once the water has boiled
  • use minimum amount of water for cooking vegetables
  • close internal doors when cooking or showering
  • leave a gap between furniture and external walls
  • dry clothes outdoors or use a vented tumble dryer
  • never dry laundry on radiators

 Ventilate to Remove Moisture 

You can ventilate without making draughts. It will help if you:

  • open bedroom windows for 5-10 minutes when you get up
  • use extractor fans in kitchens and bathrooms - leave them on longer than your use of the room.
  • if the windows are fitted with trickle vents - keep them open - apart from during the most severe of weather conditions.

Heat Your Home A Little More

In cold weather, the best way to keep rooms warm enough to avoid condensation is to keep low background heating for most of the day.

Try to keep your home properly heated. It usually helps to have a low background temperature of at least 15 degrees in all rooms.

If you have central heating, set it to provide background warmth in all rooms, including rooms that are not used. Otherwise use the thermostatically controlled heaters where necessary.

Remember to provide background ventilation at the same time!

Penetrating damp

Penetrating damp is caused by water coming through external walls or the roof.

During our investigation of condensation, we will consider if the source of moisture in the air is as a result of penetrating damp or from some other source such as an internal leak or plumbing problem.

Penetrating damp and other building repair issues is the property owner's responsibility.

Condensation and Black Mould

Fact Sheet from Propertymark:



Move with Confidence
- in the knowledge that you are protected as a seller, buyer, Landlord or Tenant.   
We are qualified members of respected property professional bodies: