Dampness and mould growth

Find out more information on the government guidance issued for both tenants and landlords.
Please see our published plan setting out how we will prioritise dealing with damp and mould.

Find out about types of dampness, get advice on how to resolve the problem and how to make a complaint if you are renting your home and have a damp and mould problem that your landlord isn’t addressing.

Dampness can appear in a number of forms in homes:

Penetrating Dampness

This is dampness inside a property that is being caused by the condition of, or disrepair to, the external structure of a property. It will tend to occur adjacent/ near the area of external damage/disrepair and can be traced back to the defect - it can be seen anywhere inside a property.

It is most common to see penetrating dampness in older properties, built before 1920, this is due to the construction type. Older buildings tend to be built using one layer of masonry to form the external structural walls, this is referred to as a “solid wall construction”. This allows moisture to penetrate more easily to the inside of the property.

More modern properties tend to be built with two layers of block or brickwork with a gap in the centre, this is called “cavity wall construction”. This gap or cavity in the modern construction, makes it far less likely for moisture to travel through the wall from the outside to affect the inside, although it can still occur.

Typical defects are to a roof, blocked or otherwise defective rainwater guttering and down pipes and damaged rendering or pointing to brickwork. This type of dampness is likely to show as staining, often with mould growth. Over time, paint work and wallpaper will peel and plaster will become perished, blown and loose.

Landlords should ensure that they inspect their properties, both externally and internally to ensure defects to the structure are identified and repairs carried out, to prevent them causing penetrating dampness. Carrying out simple maintenance like ensuring rainwater guttering is cleared of leaves and debris could save lots of money in unwanted repair bills caused by the guttering overflowing and causing penetrating dampness.

If you are a tenant and you have a dampness issue in your home because your landlord or agent is not arranging for appropriate external repairs, please see the advice and how you can contact the Council.

Dampness caused by internal disrepair issues

Dampness may be caused by defects to internal plumbing, drainage, fixtures and fittings and disrepair to means for ventilation such as windows and mechanical extract fans.

For example, leaking water tanks in lofts, hot water cylinders, water supply and drainage pipes, central heating pipework, kitchen and bathroom fittings and disrepair to tiling and surrounds to baths, showers and kitchen sinks.

This is likely to show as staining, often with mould growth. Over time, paint work and wallpaper will peel and plaster will become perished, blown and loose.

Landlords should ensure that they inspect their properties, both internally and externally to ensure any internal disrepair is identified and repairs carried out, to prevent them causing dampness.

If you are a tenant and you have dampness issue in your home because your landlord or agent is not arranging for appropriate internal repairs, please see the advice and how you can contact the Council.

Rising dampness

This occurs where there is either no damp proof course (DPC) or the DPC is damaged.

Water from the ground is drawn up through the brick/blockwork through capillary action and there is no barrier to stop it rising up the walls and affecting the property.

Very old properties may have been built with no DPC at all. Properties built pre 1950s may have had slate or similar DPCs which can fracture or fail.

More modern properties, built since the 1950s, are built with a plastic type DPC and are unlikely to suffer from rising dampness.

It characteristically appears as staining on the internal surfaces of ground floor walls starting at ground floor level and rising to a maximum height of approx 1m above ground level. You are less likely to see mould growth with this type of dampness due to the salts being brought up from the ground which prevent mould growth.

Dampness may also be caused by the ground adjacent to a property being too high and “bridging” the DPC. Ground levels should normally be at least 150mm below the DPC. If the DPC is bridged, then dampness may appear within the property. This can occur when a flower bed has been built up against the property or a new path/patio has been laid that has raised the ground levels.

This can be simply remedied by lowering the earth/paving/patio below the DPC. The provision of a French drain can help, or the provision a vertical DPC between the wall and the earth, or any abutting structure.

The provision of a DPC is specialist work involving the injection of a water-proof solution or paste/gel. It is also necessary to hack off plaster internally to a height of 1m, as salts will have been carried from the soil into the plaster. The presence of these salts in the plaster mean the plaster will not dry out and they can absorb moisture from the air and can give the appearance that there is still rising dampness, even if a chemical damp proof course has been installed. The areas require replastering using a salt retardant additive in the plaster mix.

It is best to have any works carried out by specialist contractor approved by the Property Care Association (PCA).

If you are a tenant and you have dampness issue in your home because your landlord or agent is not arranging for appropriate internal repairs, please see the advice and how you can contact the Council.


There is always some moisture in the air in our homes, from breathing, bathing, laundry and cooking.

Warmer air is capable of holding more moisture within it than colder air. So, if the air temperature is not kept high enough, or the air is cooled, say by coming into contact with a cold surface like window glazing or an outside wall, then it may not be able to hold all the moisture.This moisture will then be deposited as tiny droplets of moisture on that cold surface as condensation.

You will notice this on windows on a cold morning or on mirrors in a bathroom.

Fungal spores are all around us in the air and are on most surfaces, they are microscopic so we cannot see them. But when they have the right conditions with a damp surface to grow on, they will grow. Excessive condensation can lead to mould growth on walls and furniture, mildew on clothes and other fabrics and the rotting of wooden window frames.

Damp and mould can contribute to and exacerbate respiratory conditions. Damp and humid conditions also provide an environment in which house dust mites can easily multiply.

Steps to help control condensation and associated surface mould growth – for landlords and tenants

Controlling condensation and surface mould growth requires a balance between controlling moisture generated in the home with adequate heating and ventilation

  • Control the amount of moisture vapour entering the air in the property:
    • If you can, dry laundry outdoors.
    • If you can’t dry laundry outside, use a tumble dryer and if it's not of the condensing type, vent it to the outside.
    • If you can’t dry laundry outside and don’t have use of a tumble dryer and have to dry laundry inside, do so in a warm, well ventilated room with the window open and the door to the room shut to prevent that humid/moisture laden air from travelling around your home and depositing the condensation on cold surfaces.
    • When cooking, put lids on pans and keep the kitchen door closed and use a mechanical extractor fan if you have one, or open a window to the outside.
    • When you have a bath or shower, always keep the door to the room shut, and when you have finished, open the bathroom window for 20 minutes or so.  If the bathroom has no window, then the room should be fitted with a mechanical extractor fan.  Ensure that this is on and working when you are bathing/showering and that it continues to work for 20 minutes after you leave the bathroom.  Alternatively, a humidistat-controlled extract fan will come on when the humidity reaches a certain level and stay on until the humidity is reduced to a satisfactory level.  Close the door when you leave the bathroom.
    • Always try to open the windows in bedrooms and living rooms for a while during the day, especially first thing in the morning.  Dry the windows and cills every morning, as well as any surfaces in the kitchen and bathroom that have become wet.  Wring out the cloth, don't dry it on a radiator.
  • Control the temperature of both the air in the property and the fabric of the building:
    • Every property should have a heating system that is controllable by the occupiers, safely and properly installed and maintained. It should be appropriate to the design, layout and construction of the property, which will be affected by the type and age of property.
    • It should be capable of adequately and efficiently heating the whole property and of raising and maintaining the temperatures within the property as follows when the external temperature is –1˚C.
    • Living room and dining room 21˚C.
    • Bathroom 22 ˚C.
    • Elsewhere 18 ˚C.
    • Portable heaters, including bottled gas heaters, are not considered acceptable as these can give out large amounts of moisture which will increase the condensation problem.
    • Fixed and centrally controlled heating systems (such as a gas fired central heating system or a system of night storage heaters with a central control) are considered the most appropriate forms of heating.
    • Electric panel heaters on peak rate electric (not storage heaters) are unlikely to be a suitable form of heating, other than in small, well insulated properties.
    • Consider if the heating provided is affordable to use, the Energy Performance Certificate can help with this. This document should be issued to all tenants (other than those living in a House in Multiple Occupation) and should be dated within the last 10 years and gives an indication of fuel costs for the property.
    • Heating one room to a high level and leaving other rooms cold makes condensation worse in the unheated or cold rooms.  It is better to have a medium-to-low heat level throughout the property for longer periods of time as, in time, this will raise the temperature of the walls in the property.  If your radiators have thermostatic radiator valves to allow independent control of each radiator, use these to keep a low level of background heat in unused rooms.
  • Improve the insulation to the property to keep the heat in:
    • Look at your Energy Performance Certificate. This document should be issued to all tenants (other than those living in a House in Multiple Occupation) and should be dated within the last 10 years.
    • Loft insulation – the current standard is for 275mm of loft insulation. Check if your loft has this and get this topped up if it doesn’t. This should cover the loft hatch but allow ventilation at the eaves.
    • Cavity Walls – if your property has cavity walls (which you can tell if the brickwork is all the long face of the brick and not the shorter ends of the brick) check if these were insulated when built – this is likely for properties built since the mid-1980s. If your property was built before then, you can check if it has had cavity wall insulation added since by looking for injection holes in the external brickwork or render that have been filled, these are particularly easy to spot under window cills where they will be in a row.

The EPC should also indicate if the walls have had cavity wall insulation installed retrospectively. If the property has cavity walls and lacks cavity wall insulation, get this installed.

  • Windows and doors – double glazed window panes retain more heat than single glazed windows. Whilst the pay back on installation of double gazing in terms of saving on fuel bills is far longer than for other insulation works, replacement windows add to the comfort and appearance of a property and will reduce condensation forming on the window panes. Consider whether to have replacement double glazed windows installed, having consideration to any planning restriction that may exist.
  • Draughts – check windows, doors and loft hatches for draughts. Fix draught proofing strips where necessary.


It is important to ventilate a property to remove moisture laden air, to prevent it from condensing moisture on the cold surfaces, like the outside walls. This is still needed even in the cooler months of the year.

Use windows and mechanical extract fans, particularly in kitchens and bathrooms. To prevent cooling the property too much, close the door to the kitchen and bathroom when the window is open or fan is on, to properly ventilate that room.

If your windows have trickle vents, have these open. If your windows can be locked in a night vent position this allows for some background ventilation without cooling the temperature of the home too much.

If your property has airbricks, don’t cover these up as they provide some background ventilation.

Ensure large items of furniture are moved away from outside walls to enable warmer air to circulate to prevent condensation and mould forming on the wall and backs of sofas etc.

How to treat mould growth

  1. To kill and remove mould, wipe down or spray walls and window frames with a fungicidal wash that carries a Health and Safety Executive (HSE) approval number. Ensure that you follow the instructions for safe and effective use. These sprays are available in supermarkets and DIY stores.
  2. Clean mildewed clothes and shampoo carpets.
  3. Do not try to remove mould by using a brush or vacuum cleaner as this may only disperse the spores of the mould.
  4. After treatment, re-decorate using good quality fungicidal paint and a fungal resistant wallpaper paste, to prevent mould re-appearing. The effect of fungicidal or anti-condensation paint is destroyed if covered with ordinary paint or wallpaper.

If you are a tenant and you have a condensation dampness and mould issue in your home and you have followed all of the above advice and reported this to your landlord or agent and they are not taking appropriate action, please see how you can make contact with the Council.

If you are a landlord or tenant there are various schemes available to assist with improving energy efficiency of properties which will help to control condensation dampness and associated surface mould growth and help save money on fuel bills. Find out more information.

Find more information with this video.

Page last reviewed: 3 January 2024


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