Damp and mould growth

Damp and mould can cause or worsen respiratory problems, infections, allergies or asthma.

They can also affect the immune system, particularly in young children and those with certain medical conditions.

Damp also contributes to excess heat loss and puts up heating bills, as well as causing damage to building fabric and contents, including clothes and furniture.

There are 3 main causes of damp and mould within properties.

They are:

  • penetrating damp;
  • rising damp;
  • condensation, leading to mould growth.

This occurs when there’s a defect with the fabric of the building or services within it, allowing water to enter the property.

This could be a roof leak, disrepair to window and/or door frames or a leak from a water pipe inside the property.

Penetrating damp can usually be identified by water staining, typically yellowy brown in colour, in a particular area where the water is entering the property.

The location of this staining is generally an indication of the source of the leak/water penetration.

Rising damp is caused by the breakdown, deterioration or bridging of the damp proof course of the building.

Moisture then rises up the walls to a maximum height of around 1m.

As with penetrating damp, it can be identified by a tide mark which can be yellowy brown or can be white and textured.

This texture is caused by salts from the ground and the plaster being drawn through the wall with water.

This is by far the most common cause of damp and mould within properties, particularly during the winter months.

It can be caused by not ventilating or heating your home properly.

As the weather gets colder and heating is turned on, windows are generally fully closed.

The average family produces around 20 pints (11.4 litres) of moisture a day in an unvented property, and this moisture will condense within the property.

This moisture can cause mould growth on walls and ceilings as well as on furniture and your possessions.

How to keep your house dry and avoid condensation

Everyday activities in your home such as cooking and drying washing can create condensation which can cause damp and mould.

If your home has condensation damp then how you use your home is important.

An easy to read guide to damp an mould growth leaflet can found on the CSE website [external Link, pdf document].

Four key actions

  • Reduce the amount of moisture produced in the home
  • Provide ventilation, particularly in moisture-prone areas
  • Increase heating to raise the temperature of the air and the cold surfaces
  • Insulate the building to warm up cold surfaces and keep the heat in

There are lots of things you can do to minimise dampness and condensation in your house:

  • On dry days open some windows to allow humid air to ventilate out of the house. It is better to open a few windows a little throughout the whole house. This helps the air to move through the house. One window open wide in one room may not be as effective. Try to do this as often as possible (2-3 times a week), but keep windows closed on wet days as damp air may increase indoor humidity.
  • Do not Block ventilation - for example covering air vents, closing ventilators and switching off or disabling fans. Ventilation is needed in your home to get rid of moisture
  • Keep lids on your pots and pans when you cook – simmer rather than boil hard.
  • Keep the doors to the bathroom and kitchen closed when you are bathing or cooking.
  • Use thermal or lined curtains, keeping them open in the day and closed before dusk. This will capture the free heat from the sun and help to lift indoor temperatures.
  • Always wipe excess moisture from windows – if you don’t the moisture will collect on the frame which may start to rot. It may also re-evaporate during the day, raising humidity levels and making condensation worse when the room cools down.
  • Limit the number of pot plants in your house.
  • Install temporary plastic window insulation kits on your windows for the cooler months of the year.
  • Keep furniture away from outside walls to allow air circulation. Cool areas behind furniture will be high humidity areas conducive to mould growth.
  • Wherever possible, dry your clothes outside.
  • If you use a clothes dryer, make sure that it condenses or is vented outside.
  • If you must dry your clothes on a clothes rack inside, do this in a well-ventilated room with doors closed to the rest of the house.
  • On cold days try to keep indoor temperatures at least 18°C.
  • Try not to use a portable gas heater. They create high levels of humidity and are expensive to run. They also release harmful gases into the air.
  • Where possible install efficient heating, suitable for each of the rooms being heated
  • Install a heater in your bathroom.
  • Dehumidifiers extract moisture from the air and can help reduce humidity. However they do not tend to solve underlying problems of moisture getting into your house, excess moisture production in the home, and lack of ventilation and heating.

The Energy Savings Trust have produced a series of short videos on Warm home Hacks which are available online at:

How to get rid of mould growth

If you already have mould on your walls and ceilings then you need to clean it off properly.

You may need to get a professional to remove mould for you, but if it's only a small amount you may be able to remove it yourself.

You can easily remove the mould yourself if:

  • The area affected is less than one metre squared (3ft by 3ft)
  • The dampness was not caused by sewage or other contaminated water

To kill and remove black mould, affected areas should be wiped down a diluted bleach solution. It is strongly recommended that a disposable respiratory mask is worn, also available from more DIY and hardware stores, when removing any mould growth.

Mould should NOT be disturbed by brushing or vacuum cleaning as this can cause it to spread.

A checklist for the removal of mould (WHO, 2009) can be found below:

  • Have a big plastic bag ready to take away mildewed clothes, curtains, rugs and carpets for cleaning. Consider replacing a mattress or soft toy that smells and feels damp.
  • The process of cleaning will release mould spores into the air.
  • Open any windows but close doors tightly to help prevent the spores being spread to other areas of the house. Leave the windows open during and after the clean-up activity.
  • Prepare a bucket of water, some mild detergent, such as washing up liquid or a soap used for hand-washing clothes, and some rags that can be thrown away after removing the mould.
  • Carefully wipe the mould off the wall surface with the soapy rag. Take a dry rag to wipe down and remove the moisture following the cleaning process. Put the rags in a plastic bag prior to disposal.

After mould removal, all surfaces in the room should be thoroughly cleaned either by wet wiping or by vacuum cleaning preferably with a HEPA filter to remove spores that have spread during mould removal.

After removing black mould, a good quality fungicidal paint can be used to redecorate the affected areas.

Just removing mould is not enough, you also need to stop the dampness that is causing it.

If you don't, the problem will keep on happening.

Damp in Rented Properties

If you rent your home, you are expected to ventilate and heat your home properly so that damp doesn't build up.

The law requires you to use the property in a “tenant-like” manner. This includes:

  • reporting any repairs needed to your landlord or letting agent
  • if possible, making sure your home is well ventilated (to help avoid condensation and damp)
  • carrying out minor maintenance (such as checking smoke alarms are working and changing light bulbs)
  • disposing of all your rubbish and keeping the house reasonably clean

It is the landlord's responsibility to fix a mould problem if it is caused by disrepair.

You should tell your landlord about a damp problem if:

  • Repairs are needed for example if windows can be opened and closed securely
  • The damp is having an impact on your health
  • The damp is causing damage to furniture and belongings

Private and social landlords have a responsibility to make sure homes are fit for habitation, which means that they are safe, healthy and free from things that could cause serious harm.

As a landlord, you have a legal responsibility to keep the interior and exterior of your property in good repair.

Landlords must:

  • Carry out repairs. This includes both internal structure and any facilities relating to heating, ventilation, water using appliances and plumbing.
  • Tackle dampness including, this includes repairs that are likely to be the cause of damp and mould, such as leaking gutters. Any water damaged loft insulation should be replaced.
  • Make sure that the property is capable of being properly ventilated for example by installing trickle vents, extractor fans in a bathroom or kitchen or installing whole property positive pressure ventilation.

There is more guidance in legislation, such as:

  • Landlord and Tenant Act 1985
  • The Environmental Protection Act 1990
  • Housing Act 2004
  • Homes (Fitness for Human Habitation) Act 2018

Landlords should also check the recommendations of the Energy Performance Certificate (EPC) to see if improvements to the insulation or heating of the property can be made.

There are minimum energy efficiency standards for Privately rented properties. Since 1 April 2018, landlords of private rented properties have not been able to grant a tenancy to new or existing tenants if their property has an EPC rating of F or G (as shown on a valid EPC for the property).

For more information on Energy efficiency legislation please see our Energy efficiency legislation page.

Funding is available to improve properties where occupiers are on a low income living in low energy efficiency properties.

For more Home energy saving advice please see our Fuel poverty and home energy savings page.

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