As well as damaging the fabric of the property, damp and mould growth within a dwelling can have physiological, and social and mental heath effects on the occupants.
Any property suffering from dampness may also suffer from excess cold due to the need for additional heating to counter-act the chill effect of moisture being released into the atmosphere.
Dampness appears in a number of forms in dwellings:
This is often associated with disrepair to roofs, for example broken, missing or slipped tiles or slates. If the roof is felted then the site where the dampness appears in the dwelling may not be immediately below the area of damage to the roof as any water may travel down the felt. It usually appears as damp staining to ceilings.
Leaking water storage tanks in lofts, or airing cupboards; leaking water supply pipes; or leaking central heating pipes, may cause similar problems. Again the problem may not be immediately above the damp staining as water will travel until it finds its weakest outlet.
Remedial works would normally involve identifying the defect and repairing it at source. The structure should then dry out, although it may well leave severe staining requiring redecoration.
Normally occurs through the external walls of a property and may be caused by leaking gutters or down pipes. Also, cracked and blown rendering can trap water behind it and the longer contact time allow it to penetrate through the brickwork to appear as dampness on the internal surfaces of external walls. Again, identify the source of the problem and carry out repairs.
This occurs where there is either no, or damage to, a damp proof course. It characteristically appears as staining on the internal surfaces of walls starting at ground floor level and rising to a maximum height of one meter above ground level. Any ground adjacent to a property should normally be at least 150mm below the damp proof course, that is two courses of brickwork. If the damp proof course is bridged then rising dampness may appear within the property. This can be remedied by lowering the earth below the damp proof course, or in some cases by providing a vertical damp proof course between the wall and the earth, or any abutting structure.
The provision of a damp proof course for the first time, or chemical injection to repair a defective damp proof course, is specialist work. It may also be necessary to hack off plaster internally to a height of one metre as salts may have been carried from the soil into the plaster. These salts often 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.
It is best to have any works carried out by specialist contractor approved by the Property Care Association (PCA) (formally the British Wood Preserving and Damp-Proofing Association (BWPDA)) . They will normally provide a specialist report and sketch plan, and any works they carry should be covered by an insurance backed guarantee, usually for ten years.
In the case of the first three types of dampness it is often easy to identify the problem and find a suitable solution. Unfortunately while condensation and its associated mould growth may be easy to identify, its remedy may not be immediately obvious. It may be due to the construction of the property, inadequate heating or ventilation at the design stage of the property, or caused by the lifestyle of the occupants, or a combination of all of them.
What is condensation?
There is always some moisture in the air, whether from bathing, laundry, cooking or just us breathing out. If the air is cooled, say by coming into contact with a cold wall, then it may not be able to hold all the moisture and it appears as tiny droplets of moisture - condensation. This is particularly evident on windows on a cold morning, or mirrors in a bathroom.
Excessive condensation can lead to mould growth on walls and furniture; mildew on clothes and other fabrics; and the rotting of wooden window frames. Also, damp humid conditions provide an environment in which house dust mites can easily multiple. This can make conditions such as asthma and bronchitis, worse.
First steps against condensation
1. Control the amount of moisture vapour(i) If you can't dry clothes out doors then don't dry them over, or near, radiators
(ii) If you use a tumble dryer and it's not of the condensing type, vent it to the outside
(iii) When cooking or using the washing machine, keep the kitchen door closed and open a window to the outside.
(iv) When you have a bath or shower always keep the door shut, and when you have finished leave the bathroom window open for 20 minutes or so. If the bathroom has no window then it should be fitted with an extract fan. Ensure that this is on and working when you are bathing, 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 reduce to a satisfactory level. Close the door when you leave the bathroom.
(v) 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 sills 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.
2. Control the temperature of both the air in the property, and the fabric of the building. Air is like a sponge and the warmer it is the more moisture it will hold. 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. With thermostatically controlled, and timer operated, central heating systems this is relatively easy to set up. With other systems remember, it is better to have them on for a longer period, but at a lower temperature. The temperature in individual rooms can be boosted as, and when, needed.
If you don't have heat to all the rooms, you could keep the doors of unheated rooms open to allow some heat into them. To add extra heat to unheated rooms, or boost heat in a room, it is better to use thermostatically controlled electric oil-filled heaters or panel heaters, on a low setting, rather than a fan heater. Do not use bottled gas heaters in the home as they give out large amounts of moisture which will increase the problem.
Upgrading any loft insulation; removing any draughts; and improving the efficiency of any heating installation will help keep heat in the property and may also result in reduced bills.
First steps against mould growthFirst treat the mould already in your home, then deal with the basic problem of condensation to stop mould re-appearing.
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 its safe and effective use. These sprays are often available in supermarkets and DIY stores.
2. Dry 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 wall paper paste, to prevent mould re-appearing. The effect of fungicidal or anti-condensation paint is destroyed if covered with ordinary paint or wallpaper.
Tackle the mould