Damp and Mould

Damp and mould affects many UK homes periodically, particularly in the winter months. Many older homes as originally constructed were well ventilated with open fires and traditional glazing preventing a build-up of excessive moisture which leads to damp occurring. However modern living creates much more moisture, and coupled with the addition of double glazing this creates the perfect breeding ground for damp and mould growth. What’s more, the UK climate has a high degree of seasonal variation with mostly mild weather conditions and then a few really cold months add to the problem.

Excessive damp is unpleasant to live with and can lead to mould growth.  It can cause discomfort and distress.  It can cause damage to possessions, and to the building itself. If left untreated, it can be potentially harmful to health.  

It’s best to deal with damp as quickly as possible. Sometimes it's easy to spot the cause, but it’s not always straightforward.  There are several different types of damp and a number of causes.


Penetrating Damp

Who is responsible for fixing damp?

How can the Unipol Code help?


Tackling Mould

Mould and Health


Types of Damp

There are two main forms of damp – condensation and penetrating damp. Either type of damp can lead to mould forming.


This is the most common form of damp in UK homes.  It occurs when water vapour (moisture) in the air meets a cold building surface and condenses.

Moist air is a by-product of daily living.  Showering, cooking, drying clothes and even breathing all contribute.  

  • Surface condensation appears when moisture within the air comes into contact with a cold surface, such as a window or a cold wall
  • Interstitial condensation may occur within the fabric of the building itself 

To help avoid condensation mould developing, it is essential that occupants heat and ventilate the home adequately to manage moisture levels. 

How to manage moisture levels:

  • Open windows regularly - let fresh air in and moist air out
  • Check  ‘trickle vents’ on windows - these should be open
  • Windows (including velux windows) should have a position where they can be left secure, but very slightly open for ventilation – ask your landlord if not sure
  • Check air bricks and ventilation grilles are open and clear (sometimes they get blocked / covered by mistake)
  • Avoid a build-up of steam when cooking by putting lids on pans, and turn the heat down once the water has boiled
  • When filling a bath, run the cold water first then add the hot - it will reduce the steam by 90%
  • Check mechanical extractor fans are working properly and use appropriately Keep kitchen and bathroom doors closed to prevent moisture escaping into the rest of the house
  • Drying wet clothes indoors create a lot of moisture.   Avoid leaving wet clothes / towels to dry indoors without adequate ventilation. 
  • Dry clothes outside or in a tumble dryer.  If this is not possible, then dry clothes in the bathroom or kitchen, with the door closed and the window open / fan on.
  • Check tumble dyers are working properly.  Condensing dryers need to be emptied regularly, and vented dryers should be discharging to the outside.
  • Prevent damage to furnishings and possessions by leaving a gap between external walls and furniture / beds, etc if possible
  • Dehumidifiers can be used to remove excess moisture from the air in exceptional circumstances (eg following a leak) but it should be possible for tenants to keep moisture levels at an acceptable level by heating and ventilating properly.  When in use, dehumidifiers need to be emptied regularly.

How to provide a reasonable level of heat within the home:

  • It takes a long time for a cold building structure to warm up, so it is better to have a small amount of heat for a long period than a lot of heat for a short time
  • Whenever possible, it is best to keep heating on, even if at a low level
  • Some rooms are especially cold because they have a lot of outside walls or lose heat through the roof, and this can be worse if there are poor levels of insultation. Landlords can only rent homes that meet a minimum level of energy efficiency (currently EPC E, although this will increase to C from 2025), however this does not guarantee that all building elements will be adequately insulated, The Unipol Codes have a number of requirements regarding energy efficiency.
  • Try to keep rooms at not less than 10°C at any time, in order to avoid condensation

Landlords are responsible for ensuring heating and ventilation systems are adequate to provide a comfortable environment without excessive levels of moisture, but occupants need to use them appropriately.

Heating a dwelling adequately can be expensive, particularly in a period when utility costs are so high. However in the majority of homes if there is limited or no heating used, a level of condensation mould is likely. Even in well heated and ventilated homes, there may be some minor mould from time to time.

Penetrating damp and water ingress

This can occur when water from outside (eg rainwater or groundwater) makes its way inside the home. Water can find its way through the fabric of the building and may show up on the inside quite a long way from the point of entry (for example, tracking down inside a cavity wall) so it isn’t always easy to work out how it’s getting in. Causes can include:

  • Defective gutter saturating external walls, a roof leak, or cracks in the masonry and gaps around window / door openings. 
  • Plumbing leaks / floods caused by problematic pipework or sanitary installations (bathroom / kitchen / WC facilities).
  • Rising damp happens when moisture travels up from the ground through the walls.  It affects the walls up to the height of about one metre above ground. 
  • Basement Damp occurs when ground water seeps through the walls / floor of a basement, especially those built below the water table.  Many basements are not deigned to be a ‘habitable space’ and some level of ‘damp’ is normal and shouldn’t cause damage. 

Basements can successfully be converted into habitable space by a construction technique called ‘tanking’. Inadequate or defective tanking can lead to damp problems in basement rooms. 

Who is responsible for fixing damp?

The Landlord is responsible for fixing damp if it's:

  • caused by a repair problem - the landlord must repair the exterior and structure of the home, as well as installations like basins, sinks, baths, toilets and their pipework.
  • affecting the health and safety of occupants, or if it’s making occupants ill

The landlord is usually responsible for repairing the problem once they become aware of it, so occupants must report the problem as soon as possible in writing so there is a record.

Provide any information that might help identify the cause. Photos are very useful. Indicate the extent of the problem and the impact it is having.  

Once reported, the landlord should listen to your concerns, investigate the cause of the problem and then undertake any necessary repairs and provide advice. The landlord's response should be timely and reflect the urgency of the issue (the Unipol Code contains repair timescales that cover this). Landlords should ensure they have the necessary expertise to identify issues that might be leading to damp, or use appropriately skilled contractors. 

You should continue to update the landlord with developments, for example if the problem gets worse of if attempts to repair haven’t been effective. Repairs can sometimes be a case of trial and error, and there maybe more than one problem contributing to the damp. It can also take time for structural elements to dry out when a repair has been successful, so often there is not an immediate solution. Temporary measures like dehumdifiers and additional heating may help.

If you are concerned about damp and you have reported it to your landlord but it isn’t getting resolved, then you can report the issue to your Local Authority Environmental Heath Department or Private Sector Housing Team or complain under the Unipol Code. Alternatively there are other routes available to tenants which are summarised here.

Bradford Private Sector Housing 
Leeds Private Sector Housing
Nottingham Private Sector Housing

How can the Unipol Code help?

If you live in a Code Property then your landlord has a number of responsibilities that should help to prevent mould and condensation, and improve energy efficiency in your property:

  • Ensure the property is cleaned at the start of the tenancy
  • Undertake reported repairs within set timescales
  • Routine maintenance like gutter cleaning is undertaken at appropriate intervals
  • Properties are maintained, as reasonably practicable, free of any avoidable or unnecessary hazards as defined in the Housing Health & Safety Rating System. Particular attention should be paid to hazards such as excess cold, damp and mould, noise, falls on stairs or between levels, fire and entry by intruders.
  • Central heating is provided that is adequate, controllable and programmable by the tenants
  • Clear written instructions for the safe and energy-efficient use of all central heating and hot water systems will be given
  • Any electrical panel heater in a building, designed to comply with Part L of the Building Regulations 200217 as a minimum, is fitted with an on/off switch and 24-hour timer, or a timed booster system that allows a pre-set period of use will be satisfactory
  • All properties are provided with a minimum level of energy efficiency measures to include hot water tank and pipe lagging and adequate insulation to roof void areas, where appropriate
  • Energy efficiency improvements are incorporated, where practical, into refurbishment schemes and such schemes should comply with current Building Regulations, where applicable. Landlords are advised to concentrate on improving roof insulation (ideally 250mm depth if using conventional materials) and wall insulation with cavity wall insulation or internal insulation (dry lining). Replacing older boilers with condensing type boilers can also be effective. Energy efficiency advice can be obtained by telephoning The Department of Energy’s Energy Saving Advice Service on 0800 444 202;

A full copy of the Code standards can be found here

You can check if your property is covered in the Code here

If you feel that the Code is being breached, you can make a complaint here


Moulds are a form of fungus.  There are many different types.  They produce spores which spread by floating around in the air.  These spores are present in all environments, both indoors and outdoors. 

Mould spores thrive in moist environments, which is why occupants should try to prevent excessive moisture and adequately heat properties.  When they land on a damp spot, with a supply of suitable nutrients, they begin to grow.  Mould can grow on a variety of different surfaces, including fabric, paper, wood, glass, and plastic.

Mould growth is usually visible and often produces a musty odour. It can damage household items.

Tackling mould

Regular cleaning and wiping can sometimes reduce the risk of condensation mould appearing or getting worse. As excess moisture and minor condensation mould is quite common (especially in colder months), occupants are usually expected to attempt to wipe it off when it arises. An example of this would be wiping down a window sill or bathroom wall where a small amount of mould had formed.

You can wipe hard surfaces with a suitable mould cleaner or fungicidal wash, carefully following the instructions.  Dry surfaces well to prevent mould from reappearing.  Porous surfaces can be washed, but check regularly to see if mould has returned.  If mould has infiltrated the material it may need to be disposed of.  There is a useful video with instructions here.

If you are unable to safely clear condensation mould from your home (for example if you have a health condition or cannot easily reach it) then you can ask your landlord to clean the mould.  If the mould covers a large area, appears to be linked to disrepair or returns very quickly after wiping, you should ask your landlord for help.

When mould has been cleaned away, surfaces can be repainted with a good quality fungicidal paint to prevent re-occurrence. But if the problem returns quickly, the landlord may need to consider further measures.

Mould and health

Mould should be dealt with promptly as it can present a health risk if left untreated. A small amount of mould for a limited period of time doesn’t usually present a risk for healthy people.  However, mould can pose a health problem for people with compromised immune system, an allergy, an existing respiratory problem, or a certain other risk factors, or for healthy people if left untreated for a long period of time.

If you believe mould is causing a health problem you should see your GP for medical advice, and let your landlord know so they can take action.