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A guide to Damp and Condensation

The difference between damp and condensation

Damp occurs when a fault in the building's basic structure lets in water from outside.
Penetrating damp

There are two types of damp, penetrating damp and rising damp.

Penetrating damp occurs when water is coming in through the walls or roof, (for example, under a loose roof tile, leaking pipes or waste overflow) or through cracks.

Rising damp
Rising damp is rare but if this occurs there is a problem with the damp proof course. This is a barrier built into floors and walls to stop moisture rising through the house from the ground. The usual evidence of rising damp is a 'tide mark' on the walls that shows how high it has risen. There is also a musty smell.

If your home suffers from any of these damp problems, please contact the housing repairs team.

What is condensation?

There is always some moisture in the air, even if you cannot see it. You notice it when you see your breath on a cold day, or when the mirror mists over when you have a shower or bath.


Condensation is caused when moisture held in warm air meets a cold surface like a window or wall and condenses into water droplets. If this happens regularly, mould may start to grow. This usually appears on cold outside walls and surfaces and in places where the air does not circulate well. The moisture created can also damage clothes, furnishings and decoration. It leaves a musty smell.

Condensation can aggravate health problems like asthma, bronchitis, arthritis and rheumatism.

What causes condensation?

Condensation usually occurs in winter because the building is cold and windows are opened less so moist air cannot escape.

Does it have a 'tidemark' effect? If yes, this is not condensation, it is damp. It could be caused by rain seeping through windows, or rising dampness due to a defective or missing damp proof course. Please contact us so we can investigate the problem.


Is your dampness caused by condensation?

There are three main ways to tackle the problem

1. Stop moisture building up

  • Wipe down surfaces where moisture settles.
  • Cover boiling pans when cooking.
  • When cooking, bathing or washing and drying clothes, close kitchen and bathroom doors to prevent steam going into colder rooms, even after you have finished.
  • Cover fish tanks to stop the water evaporating into the air.
  • Dry clothes outside where possible.
  • Do not hang washing over radiators.

2. How to ventilate, or air, the home

  • When cooking or washing, open windows or use extractors.
  • Where drying clothes inside is necessary, do so in a small room with windows open.
  • Open windows for a while each day or use the trickle/night vents.
  • Do not block air vents, this is also important where gas and heating appliances are concerned as they need a supply of oxygen to work effectively and allow gases, such as carbon monoxide, to escape.
  • Allow air to circulate around furniture and in cupboards, you can do this by making sure cupboards and wardrobes aren't overfilled and there is space between the furniture and the wall.

3. Keep your home warm

  • Draught proofing will keep your home warmer and help reduce fuel bills. When the whole house is warmer, condensation is less likely to form.
  • Insulating your loft and walls will help. If yours are not insulated, please contact us for details of work planned for your area or advice on energy efficiency. 
  • Maintain a low heat when the weather is cold or wet, this is more effective than short bursts of high heat.

Always ensure that you do not

  • Block permanent ventilators e.g. airbricks or trickle/night vents.
  • Completely block chimney. Instead leave a hole about two bricks in size and fit a louvered grille over it.
  • Draught proof rooms where there is a cooker or fuel burner heater, for example, a gas fire.
  • Draught proof windows in the bathroom and kitchen.
  • Do not disturb mould by brushing or vacuum cleaning. This can increase the risk of respiratory problems.

First steps against mould

Mould is a living organism and needs killing to get rid of it. To do this, wipe down effected areas with a fungicidal wash; one which carries a Health & Safety Executive approved number, making sure you follow the manufacturer's instructions.


Dry clean mildewed clothes and shampoo carpets. Distributing mould by brushing or vacuum cleaning can increase the risk of respiratory problems.

After treatment, redecorate using a good quality fungicidal paint to help prevent mould reoccurring.

Note that this paint is not effective if overlaid with ordinary paints or wallpaper.




What to do next

If you are a Powys County Council tenant:

Contact the Housing Repairs Team

More information about the repairs service can be found at: Ask for a council housing repair

If you live in privately rented accommodation:

  • You should notify your landlord / agent in writing of disrepair problems you have in your home. This can be done by email, text or by letter but please keep all copies of any correspondence.
  • It is essential that you give your landlord or their agent the opportunity to fix the problem in a reasonable timeframe.

For further information please visit: Report an issue with housing conditions