Damp in your house will be caused by one or more of the following:
- Condensation
This is the most common, and probably the most complicated, cause of dampness. Condensation occurs when relatively warm moisture-laden air comes in contact with relatively cold surfaces and the water vapour condenses on the surface. It occurs most often in winter when houses are least ventilated and when uninsulated external walls, windows, and so on, are at their coldest. Different parts of a building are affected by very different micro-climates. For example, north facing elevations can be subject to prolonged damp, as they do not receive the benefit of a drying sun and are usually sheltered from drying winds and south-west facing elevations are subject to fluctuations in temperature and regular wetting and drying cycles – the elevation of the walls and the insulation in the walls of a house will affect how cold the wall is and therefore how susceptible to condensation the wall is.
Condensation is particularly affected by people’s management of their homes.
Signs of condensation are often grey or black-spotted mould growth on walls and ceilings, particularly to areas with least air movement, such as corners or recesses, and colder areas of construction around windows and doors, or below uninsulated roofs.
To help prevent condensation:
- Produce less moisture –
- avoid hanging wet/damp items indoors – dry wet clothes outdoors or in a tumble dryer
- vent tumble dryers to the outside or use a condensing dryer
- cover pans when cooking
- do not leave kettles boiling
- when using the bathroom or kitchen close the doors to prevent moisture in the air spreading to other parts of the house
- Remove excessive moisture –
- open any trickle vents fitted in windows
- when using the bathroom or kitchen make sure air extraction systems are switched on and working and open any windows
- after using the bathroom or shower keep the door closed and continue to ventilate the room using any air extraction system or open any windows to allow the moist air to escape
- wipe condensation from windows and window sills immediately it appears
- when condensation appears on cold surfaces such as mirrors or windows, use any air extraction system or open any windows to allow the moist air to escape
- ventilate bedrooms by opening bedroom windows after you arise
- use a dehumidifier to remove excessive moisture. Set the dehumidifier to maintain a humidity level of 45-55%. Aside from just removing moisture, using a dehumidifier has health benefits – see Ebac reference below. Small pots of desiccant available from local supermarkets and hardware stores will not remove all excessive moisture.
Finally, a few other things to consider when addressing condensation damp:
- The warmer a surface is, the less likely moisture will condense on that surface, so adequately heating the property is helpful in preventing damp caused by condensation.
- Special paints claiming to resolve damp in your home will not prevent moisture being produced, will not remove excessive moisture and will not heat surfaces.
- Houseplants are a good way to help alleviate the problem naturally, by bringing moisture levels down in the air: English Ivy, Peace Lily, Palms, Snake Plants, Boston Ferns, Orchids, Spider Plants.
- Penetrating Damp
Moisture – usually rain, occasionally floods – penetrating the interior of the house from the outside, under wind or gravity. There are many parts to the ‘envelope’ or external skin of a house – roofs, walls, windows, doors, chimneys and so on – each of which has their own sets of components (for example, in the tiles, slates, flashings, copings, ridges of roofs) and each of these components has its own role to play in keeping out the weather. Consequently, damage, deterioration or dislodging of even individual components can lead to penetrating damp or a full-scale leak, though such is the complexity of construction, particularly modern or modernised construction with its multiple layers, that the symptoms may not necessarily appear where they are expected.
The visual signs of penetrating damp may well seem similar to those for rising damp but they usually relate more specifically to local sources and will, therefore vary markedly around the house; for example, a sheltered wall may appear dry, whereas one exposed to driving rain from the prevailing westerly wind may be seriously affected, or even more specifically, a spreading vertical damp patch that is worst at the top of a wall may relate to a leaking rainwater pipe or broken gutter.
- Rising Damp
Moisture from the ground rising in porous wall construction by means of capillary action. Visual signs are a ‘tide mark’ of damp staining or decayed finishes above local external ground levels. For residential buildings with thinner walls the average rise height of rising damp is around 1m, however it can rise significantly higher for thicker walls.
- Leaking Services
Leaking pipes and drains within the property, wet appliances, sanitary ware and bath and shower seals can all cause damp. Leaking water supply pipes can be particularly troublesome as the flow of water will be continuous rather than intermittent. Leaks can happen in voids between floors and ceilings so may go undetected for some time.
Further Reading
The Damp House: A Guide to the Causes and Treatment of Dampness by Jonathan Hetreed
Keep your home free from damp condensation and mould – Landlord Accreditation Scheme – North and Central Staffordshire
5 Surprising Benefits A Dehumidifier In Your Home Will Help With – Ebac
What is causing black mould in my house? {Jungle Property Knowledgebase article}
How do I treat black mould in my property? {Jungle Property Knowledgebase article}
Still not answered your question? We love questions so fire it at us using the contact details here
Please rate this article so we know how well it answered your question…
