Correct Identification of damp problems and building defects is essential if the right treatment is to be given. Incorrect diagnosis and leaving defects can lead to very expensive and disruptive remedial measures.
The greatest of deterioration in buildings is from the ingress of moisture. It is one of our main aims to ensure that the fabric of the building is free from moisture ingress
Some effects of dampness are easily visible for example, damaged decorations, decaying timber, black mould growth, deterioration of floor coverings etc.
Each problem of dampness must be looked at individually and the cause correctly diagnosed before a method to cure the defect can be undertaken.
There are basically four main areas which can cause dampness in buildings
1 - CONDENSATION
2 - RISING DAMP
3 - LEAKING PIPES
4 - INGRESS OF MOISTURE
There is always some moisture in the air, even if you cannot see it. If the air gets colder, it cannot hold all the moisture and tiny droplets of moisture appear. This is known as Condensation. It appears on cold surfaces and in places where there is little movement of air (eg. In corners, on / near windows, behind wardrobes). Mould growth is associated with condensation and can be found on damp surfaces such as plaster, wallpaper and timber.
There are steps you can take to reduce Condensation;
PRODUCE LESS MOISTURE
- Cover Pans
- Dry washing outdoors
- Vent tumble driers to the outside
VENTILATE TO REMOVE MOISTURE
- Keep a window ajar or a trickle ventilator open
- Ventilate kitchens and bathrooms with a window open or by using a humidistat controlled fan
- Close kitchen and bathroom doors when rooms are in use
INSULATE YOUR HOME
- Insulating lofts / cavities will keep the building warm
- In cold weather, keep low background heating on all day, this raises the room temperature.
Rising Damp does exist, however it is not as common as is made out by many damp proofing contractors. Rising Damp usually occurs in walls where the foundations extend down below the ground water table. The water rises either through the bricks or the mortar joints due to fine capillaries or pores in the materials (A process known as Capillarity). There are three main factors that affect the quantity of moisture absorbed by the wall and the height to which it rises;
- The capacity of the wall material to absorb moisture.
- How wet the ground is.
- How quickly the moisture can evaporate.
Water will continue to rise up the wall until it meets with a physical barrier, The construction of most modern buildings includes a' damp proof course (dpc) - a layer of impermeable material (eg: slate, bitumen, plastic) built into the external walls just above ground level. The dpc prevents moisture rising within the wall construction. In the absence of a damp proof course (DPC), then the water will continue to rise up the wall to a maximum of 1.5m. Many situations where rising damp occurs is often due to the bridging of the existing damp proof course rather than the absence of one. Older buildings, particularly those with solid stone or brick external wall, do not always have a dpc. It is assumed that rising dampness is likely to be a problem in these type of properties, however a full investigation of the cause of dampness must be carried out to determine if rising damp is indeed the cause.
A small leak in a water supply, central heating or internal drainage pipe can cause extensive dampness over a period of time. Signs of dampness though may only appear some distance from the leak.
Spills from water tanks, cisterns and washing machines can cause water to run through cracks or joints. This can spread underneath floor coverings causing further problems.
Water ingress will occur where the building is unable to prevent water entry where water is present. Water can be driven in by wind and rain, attracted by salts and drawn towards the warmth. Penetrating dampness can occur through many building defects, examples include;
Rainwater goods - Blocked valley gutters and downpipes can cause rainwater to 'pond' and overspill the flashings. Parapets and chimneys can also get very wet, with water draining downwards to other parts of the building causing damp patches inside.
Leaking roofs - Common defects of roofs include corrosion of nails that fix the tiles to the battens, cracked or missing roof tiles, mortar missing from ridge tiles. These defects can all allow the passage of moisture into the building
Plaster Rendering - Defective plaster rendering can occur mostly on external walls caused by penetrating rain, evaporation and condensation. These thermal stresses can cause shrinkage and cracking of the render.