Penetrating damp – where leaks can lead in winter storms

ThinkstockPhotos-489384250With storms like Abigail, Barney and Clodagh, it has been a very wet and windy autumn so far. The UK is in the path of the polar jet stream (the boundary between warm and cold air). It’s along this boundary, where pressure gradients are tightest, that storm systems travel. The tropical air to the south has been absorbing heat and moisture from the oceans, and as cold air sinks south over our latitude, the two air masses collide and brew up storms and persistent rain!

These storms, with driving winds and relentless rain, can lead to penetrating damp problems. This is the process of lateral damp penetration whereby water gains access to the fabric of a property (not to be confused with rising damp). Water from damaged rainwater goods, leaking pipes, cracked render, wind driven rain (particularly on solid walls) or groundwater passing through basement earth retaining walls, can contaminate the building fabric and may cause external salting (efflorescence) of the masonry.

Wind driven rain can cause large amounts of water penetration, particularly to solid walls.  As the water dries out, salts in the building materials are brought to the surface and efflorescence (which means “to flower out” in French) is likely to appear. If the wall is rendered you may feel it is protected, but if there are cracks, these cause water to run in to the masonry and then the render stops it drying easily.

Penetrating Damp due to damaged rain goods imageDamp may appear on the inside of external solid walls, on ceilings below flat roofs or where slates/tiles are missing on pitched roofs, on chimney breasts or around doors/windows after heavy rain. There may be leaking pipes or a gutter tipping water backwards onto a cavity wall. Surface runoff, particularly where the property is surrounded by hard surfaces such as parking spaces or paved front gardens can lead to penetrating damp issues.

Earth retaining walls below ground level, such as in basements or properties built into a slope, may also suffer from ground water penetration.

Here are some of the signs of penetrating damp to check for around your property:

  • Internal decoration – damp, discoloured tidemarks on walls, in line with external ground level
  • Damaged Plaster – blistering, salting and disintegration of plaster on walls
  • Rotting timber – skirting boards and/or floor timbers (possible wet rot decay)
  • Localised dampness – Random damp patches that do not dry out

penetrating damp plant damage to bricksIt is important to keep all rainwater goods clear of debris – if they fail during heavy storms, water can easily find its way into your property. The same is true of plants growing on buildings. It’s not uncommon to find plants like buddleia sprouting from a chimney stack.  Once the roots take hold they can easily penetrate masonry, letting water in.

Penetrating damp and the resultant damage to the fabric of a building, plaster surfaces and potential timber decay can be very damaging and costly. It is very important to correctly distinguish between damage caused by penetrating damp and other damp problems such as rising damp or condensation. Correct diagnosis by a professional, specialist damp surveyor can help prevent unnecessary expense on solutions that will not solve the underlying problem, and provide the most effective treatment to resolve the damp issue.

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