There are three ways water can get into the fabric of your house and start to cause damage:

Rising damp

When water from the ground gets into solid walls or floors and finds a way through your damp proof course (dpc), the result will be rising damp. The dpc in your walls may be either:

Blue Brick

In older houses there are two courses of darker bricks that are waterproof.

With age these bricks let water through, into ordinary bricks and out through your plaster.

Slate or Plastic

This is a barrier fixed firmly in the mortar between two courses of bricks. The mortar joint will be wider for this joint than the others. This type of dpc should not cause a problem unless the wall is affected by movement.

Chemical

You will see a line of holes in your wall. This is where a chemical has been injected to bricks above an old blue brick dpc. The chemical fills all the voids in the bricks and stops water getting through. When a specialist contractor injects a chemical dpc a ten-year guarantee is normally issued.

Solid floors

Whilst modern floors have a plastic sheet beneath the concrete to prevent water coming through, older floors do not. Where old floors still have their original quarry tiles the joints between the tiles may have broken down to allow damp through from the ground.

Rising damp to most ground floor walls probably means that a chemical dpc is required. If it appears in only one wall or to a small area, then water may be finding a way around the dpc. This could be through soil piled against a wall, paving raised above the dpc or rendering which covers the dpc. In these cases, removing the route the water takes should cure the problem.

Dampness through old quarry filed floors will usually require their replacement with a new concrete floor complete with a plastic sheet damp proof membrane (dpm).

Penetrating damp

This is where water gets into the building from outside. You will see a damp patch a bit like a stain from a spilt drink and it indicates that a repair is needed. This may be to the roof, flashings, gutters, rainwater pipes, waste pipes, window sills, brickwork or pointing.

This is where water vapour in the air in the house condenses on a cold surface. It normally appears on windows in the early morning and evaporates harmlessly as the house warms. It may also appear on toilet cisterns and cold water pipes but is only a problem when water vapour condenses on cold walls and black mould begins to appear. A wall may be cold and attract condensation for several reasons:

walls to the back addition of older houses are more exposed and so may be colder

it may only be a 4 inches thick brick wall, especially where an old external toilet or coal house has been demolished or incorporated into the main house

it may be facing north or the room may be unheated

a leak to a gutter or pipe may make part of a wall cooler

Water vapour

This is created by normal, everyday living in your house such as washing, cooking, bathing, drying clothes, breathing and burning fuel. The average family produces 20 pints of moisture every day. You can reduce this by:

• keeping lids on pans when cooking
• drying clothes outside or have a pipe taking the tumble dryer’s moisture outside
• running the cold water for a bath before the hot water
• not using liquid paraffin or bottled gas room heaters

Ventilation

This is the normal escape route for moist air. As the air in your house circulates, it is drawn outside through open windows, doors, extractor fans, air bricks and chimneys and is replaced by fresh air. If this exchange of air is prevented the air in the house will become saturated and will condense on the nearest cold surface. To allow air to circulate and be exchanged for fresh air you should consider some of these:

• fit extractor fans to bathrooms and kitchens
• open windows
• keep bathroom and kitchen doors shut to prevent moist air circulating to the rest of the house
• avoid still air pockets - areas between furniture and external walls and behind curtains may trap air which will condense as temperatures drop. Move furniture away from these walls for an hour or so as often as you can and don’t leave heavy curtains closed during the day.

Heating

Warm air can hold more moisture than cold air so if your house is heated you are less likely to suffer from condensation. Warm air cooling in the night will still result in condensation, especially on windows during cold and wet weather. Most of this will evaporate as heating is turned on again in the morning and windows are opened.

Insulating your house 

Loft insulation, wall insulation and double glazing will mean you keep the heat in your house longer, walls are warmer and the chances of damaging condensation are greatly reduced.

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