Tag Archives: Condensation

How to Deal with Damp

If the weather is wet and muggy and damp patches appear on walls and floor then the problem is damp. Damp is caused by such things as broken tiles, defective flashing cracked down pipes and gutters. All these must be fixed immediately or the trouble will spread – it is no use redecorating hoping all will be well – it won’t. Usually the rain which is absorbed by the house walls dries out when the weather is dry. Sometimes, however, the water reaches the interior house walls. This can happen for a number of reasons.

Most modern houses are built with cavity walls, that are an inner and outer wall separated by an air cavity. The two walls are held together with steel ties. Normally there is no way that rainwater can cross the cavity and reach the inside wall (the steel ties are constructed to prevent them forming a ‘bridge’). However, if, during wall construction, mortar is allowed to drop on to the ties a ‘bridge’ will be formed and the rainwater will cross. Painting the outside wall with a silicone water repellent is the answer here. This seals the brickwork against rain but still allows the bricks to breathe so that trapped moisture vapour can escape. Not all solid walls give rise to damp problems but many do. The more exposed walls facing the prevailing winds from the south-west are most likely to be affected. Damp patches in severe cases could extend over an entire internal wall.

Wall Damp How to Deal with Damp

Here again, a coat of silicone water repellent will help. Other safeguards against water penetration are to make sure the pointing between the bricks is in good condition, and any exterior grade decorative paint will also help. Gaps around windows must be sealed. These gaps round a wooden window frame will widen and narrow as the frame expands and contracts in its normal seasonal movement. It is no use filling them with Polyfilla or other cellulose filler; this will crack up and fall out after a short while. Use a mastic compound. This material is fixable and will expand and contract along with the frame, thus keeping the gaps permanently sealed.

If the brickwork of the house walls is porous and the wall ties in the cavity between the inner and outer walls were covered with mortar droppings when the walls were built, then the ties form ‘bridges’ for rainwater to cross to the inside wall. Brush a proprietary damp resisting liquid, usually silicone solution, on to the outside wall. Seal any gaps between door and window frames and brickwork with a proprietary flexible mastic sealer. Do not use cellulose filler as this will crack and eventually fall out due to normal movement of the timber frame.


The damp-proof course in the house wall prevents damp rising above the first few brick courses. Take a look at the lower part of the wall’ you should see a horizontal layer of material set into the pointing. This material spans both walls of the cavity and is usually slate or bitumen felt. It continues, unbroken, around all the walls. Normally damp will be stopped when it reaches the damp-proof course. However, should earth be piled up against the wall or path raised to near the damp-proof course level there could be problems. The damp-proof course will be bridged and moisture from the earth will soak into the bricks. In heavy rain, water could splash up about it from the raised path. So keep earth piles away from the house wall and make sure that the damp-proof course is at least 6in. above the level of paths. If you have to, then lower the lever of a path by break it up and re-laying it. Or else apply cement to the house wall to form a skirting. The cement must contain a waterproof agent, but whatever you do, it is worth while applying a water repellent liquid to the wall as well. If the existing damp-proof course is faulty there are several firms who will carry out one of a number of methods of curing the trouble. Their addresses are in the yellow pages directory. You can do the job yourself, though, using a damp repelling liquid – Stroma is one make. There are two grades – one for the inside walls and one for the outside walls. This liquid forms a barrier by penetrating right through the brickwork. In older properties there may not be a damp-proof course at all. In days past, builders often relied on the thickness of material to prevent rising damp – and often it did not work. The firms referred to above will help here, but hey use systems which have to be carried out by specialist.

Rising damp can be caused by earth piled against the house wall over the level of the damp proof course or by a blocked airbrick. If these are not the causes get specialist advices.

How to Deal with Condensation

Damp and condensation are tow of the greatest nuisances of winter. Wet patches appear on ceilings and walls, ruining decorations, while moisture runs down windows to form puddles on sills, eventually breaking up the paintwork and causing the wood to rot. Damp and condensation are entirely different things though their effect is basically the same. Before remedial action can be taken, you have to establish which of the tow is causing the trouble.

Condensation is caused by warm, moist air contacting a cool surface. Moisture on kitchen and bathroom widows or beds of water on ceramic wall tiles are the more obvious signs. Damp patches on living room walls are another tell-tale sign. The air is moistened by such things as steam from cooking, washing, burning paraffin heaters – even breathing. These combine to raise the room temperature and load the air with water vapor. When this moist air contacts a cool surface, the water vapor condenses on it. So on a cold day, streaming windows and damp patches on walls indicate condensation. To combat condensation, four things can be done. Keep room warm, dispose of steam and water vapor, provide ventilation, and avoid cold surface.

Condensation How to Deal with Condensation

The kitchen and bathroom should be the main place to watch as most of the troubles spring from there. An extractor fan fitted in a window will help to remove water-laden air. The manufacturers of the fan will tell you the recommended thickness of glass needed to support a fan. When cutting circular hole for the fan with a glass-cutter use a pre-made template as a guide. Make tow concentric circles – the largest being the required size for the fan. Score a series of criss-cross lines inside the smaller circle before tapping out the small squares formed, starting from the center. Repeat the process on the larger circle until this glass is all tapped out. If you have to fit new glass, ask your supplier to cut the hole for you. Most fans are easily fitted in tow or three stages. Follow individual makers’ instructions closely. Very cold bathroom walls can be kept warm by fitting a black tubular heater that operates at 60 watts per foot.


Line the ceilings with expanded polystyrene tiles. These give good insulation value and resist condensation forming. Use flame-retardant types in kitchens or in any room where fire is a risk.

Fix flame retardant polystyrene ceiling tiles to bathroom and kitchen ceilings to reduce condensation forming. Cut the tiles with a Stanley-type knife, held against a straight-edge. Press down firmly on the knife to make a clean cut. Spread the special adhesive all over the back of each tile before fixing in place.


It is fashionable to block off fireplaces nowadays. The fireplaces used to provide ventilation; by blocking them in, ventilation is reduced or cut-off completely. Always allow for an air-brick when bricking up a fireplace. No flow of air in the chimney can cause damp patches on living room walls, especially on chimney breasts. Paraffin or oil heaters contribute towards condensation problems. Radiators, electric convectors or radiant fire – any dry-heat types in fact should be used. Even with these, however, correct ventilation is needed. An open window or a ventilator that can be controlled will enable you to allow the correct amount of air into the room according to seriousness of the condensation problem.


The simplest way to insulate walls against condensation is to line them with sheet expanded polystyrene which is sold in rolls at decorating shops. Wallpaper can be applied over the polystyrene in the normal way. Cavity wall insulation is another method of wall insulation.


Less of a problem, usually, is condensation on solid floors. Many people imagine that damp patches are a sign of rising damp. There is a mile way to find out if they are. Fix a small piece of glass to the floor with putty all round its edges so that air is trapped in the space between the glass and the floor. If moisture forms on the bottom of the glass (after a short while) the problem is rising damp. If the moisture appears on the top of the glass, then you are up against condensation. A good underlay beneath a carpet will help, as will a build-in foam underlay on any sheet material. Under linoleum or vinyl, fit a cork underlay or a reflective-faced building paper.

A blocked off chimney means it is no longer ventilated. Eventually damp patches will appear on the breast. An air brick or grill must be fitted in every room. Mould, mildew or fungus on walls means having to strip off the wallpaper. Wash the wall with a fungicide before repapering, and use a paste containing a fungicide. Walls affected by condensation should be lined with sheet expanded polystyrene. This is bought in rolls and can be papered over in the normal way.

Strip off the old wall covering and hang the first length of polystyrene. Your supplier will advise you on the special adhesive needed to stick it to the wall. Use a roller to sharp Stanley-type knife at the skirting and ceiling line. Press down hard with the knife to cut the material cleanly. Carefully butt the edges of successive lengths.


Double glazing will help against, though may not always cure, condensation. Anyone with double glazing already installed who still gets condensation will find that some silica gel crystals (available from chemists) placed between the panes of glass will help. These absorb all the moisture, but they eventually become saturated and have to be dried out in an oven before re-use.

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