Condensation And Mould Guidelines For Tenants

April, 2024

Condensation occurs when warm, moist air comes into contact with a cooler surface. The drop in temperature means it can no longer hold on to the same amount of moisture it was retaining, and the water is released onto the cooler surface.

Condensation can occur naturally as a result in temperature changes or artificially by the actions of tenants. In the UK, it is often a winter problem (September-March), usually caused when warm moist air comes into contact with colder areas of the property.

Excessive condensation can lead to mould growth on window frames/sills, walls (usually external walls), ceilings, furniture and tenants clothing.

The 2 main steps a tenant can take to prevent condensation are:

1-      Increase the ventilation within the property. This will remove moist air from the building, so it doesn’t come into contact with colder surfaces.

2-      Maintain a consistent temperature. This will help stop the structure of the property becoming cold.

Action to be taken against mould growth, in the first instance, treat all mould in the property with either a specific mould spray or a very weak bleach solution. Once completed, refer back to steps to prevent condensation and monitor carefully. Please follow all safety instructions and wear appropriate gloves, if applicable. Some people do not realise that even breathing will create moisture in the air.

Most of a tenant’s general day to day activities within the property will add extra moisture. Below are a few examples of how much moisture this could be:

1-      2 people at home, just breathing-3 pints

2-      A bath or shower-2 pints

3-      Drying clothes indoors-6 pints

4-      Cooking and use of the kettle-3 pints

5-      Washing dishes-1 pints

Total moisture created in ONE day = 15 pints. The above illustrates how much extra moisture is created per day for 2 tenants.



Increasing ventilation will significantly help in the fight against condensation, it removes the warm moist air within the property and replaces with fresher drier air from outside.

Cross-ventilating your property is the best step to correctly and efficiently ventilating your home. Try opening 2 windows downstairs, 2 windows upstairs and allow for the air to flow through, this will increase the air flow, therefore increasing the warm moist air taken out and increasing the fresher drier air from outside.

We accept, that this is not always easy during the winter months, when it is cold, but condensation and mould forming from poor ventilation is a tenant responsibility. It is cheaper to pay to re-heat your home than having to pay towards redecoration costs at the end of your tenancy.

Some steps to help increase ventilation:

1-      Ventilate your kitchen when cooking or washing up. A window slightly open makes a difference. If you have an extractor hood, use it, most are vented to the outside and will take the warm moist air away, decreasing the amount within your kitchen. When you finish cooking, leave the window, or extractor hood, on for 20-30 minutes.

2-      When showering/bathing, ensure you always use the extractor fan, if one is fitted. Leave the extractor running for a further 20-30 minutes after showering/bathing per use. If your extractor fan is found to be turned off, you will be responsible for the cost of works to rectify mould issues. Not correctly ventilating your bathroom will result in mould forming to the sealant and grouting as well, not just the walls and ceiling. The extractor fan is cheaper to run that paying for the bathroom to be redecorated.

3-      Some windows will be fitted with trickle vents, or night latches. These allow for a small amount of air to circulate securely. Ensure these are open to help prevent condensation and mould.

4-      During the day, open curtains/blinds. This allows air to the windows and frames, it also stops the back of the curtains and the window sealant going mouldy. Any mould from condensation to the curtains or sealant, will be tenant responsibility to rectify. Steam cleaning curtains and resealing windows will cost!

Precautions to take:

1-      Keep kitchen and bathroom doors closed to prevent the moisture escaping into the rest of the property.

2-      Do not over fill wardrobes/cupboards, this restricts air circulation and can increase mould or mildew on your clothes.

3-      Leave small gaps between all large items of furniture and the walls. Divan beds against an external wall, this is a must.

4-      Divan beds allow very restricted air flow thus increasing the chances of condensation and mould.



Keep the heating on at a low temperature all day in colder weather, this will help control condensation. A medium heat throughout the property is more beneficial than heating one room to a high level and leaving other rooms cold.

If you have turned the heating off in one particular room, keep the door open to allow for heat and air flow in that room.

Most homes take a long time to warm up and it may cost you more to try and heat up your home quickly in one go in the evening. The warm air in the property will hold more moisture, the higher the moisture and warmer the air, the more likely it is condensation will form. Air acts like a sponge.


Mould grows on the sealant and grouting for 2 main reasons:

1-      Poor ventilation and excessive water left on the sealant/grouting

2-      The sealant has deteriorated which has allowed water to escape behind it. The warm moist atmosphere of a bathroom is the perfect mould growth.

How to prevent the mould growing in the first place:

Wipe down all surfaces after use to remove excess moisture from the tiling and edges of the shower tray/bath.

As above, ensure the extractor fan is in use and left on for 20/30 minutes after use to allow it to remove excess moisture ensuring the bathroom door is closed.

If you can, open the window to allow excess humidity to escape however do not leave it open for so long that the bathroom becomes cold and damp (during Sept-April).

How to Remove mould from sealant/grouting

Try undiluted white vinegar applied directly to the sealant, allow it to sit for at least 1 hour or even overnight.

Using a cloth or toothbrush, work the vinegar in a circular motion until the mould starts to come away. Clean and wipe afterwards. If the mould seems stubborn, mix the vinegar with bicarbonate of soda to make a paste, apply over the sealant and leave overnight. Repeat the removal process. The final option is to apply bleach and cover with wet toilet roll, leaving it overnight. If the mould is still present after this method, then the sealant needs replacement. If the mould has formed due to your tenancy obligations not being met, then the cost will be yours to cover.



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