British weather has always been a bit of a joke. In fact the average British house has to deal with around 113,000 litres of rainwater every year. Most is channelled harmlessly away from your property by gutters and drains, but occasionally something can go wrong and rain water could cause a problem. Broken gutters, poorly designed decking and patios, and poor ventilation can all lead to a potentially serious damp problem. And once inside the structure of the property moisture can dissolve plaster and paint, rot wooden frames, and cause mould on interior surfaces. This can have disastrous consequences for your homes structural integrity, not to mention the health problems that can arise as a result of damp. Mould on interior surfaces (right) release spores inside your home which can cause respiratory problems and infections.
You may think that as housing has improved the problem of damp won’t be as bad as it used to be, but in fact the opposite is true and more measures need to be taken to adequately prevent it. In the late 19th and early 20th century houses were naturally draughty, and the continuous airflow prevented the build-up of mould. Nowadays modern paints and building materials, and an aversion to draughts have led to poorly ventilated rooms. I recently moved into a fairly modern home and began to see the signs of damp developing. It was only on much closer inspection that I saw that the previous tenant had painted over the vents in each room. Once I had unblocked the vents the damp cleared and the property even felt slightly warmer as a result. So the first tip I can give you is don’t be afraid of opening a window slightly even in the winter.
Dealing with interior symptoms of mould is all about achieving a fine balance between insulation and ventilation. Is your property adequately insulated? Almost all properties with a loft space should have loft insulation, and newer properties should have cavity wall insulation. There are all sorts of government subsidies in the UK to make insulating your property affordable, and you should notice a substantial drop in your energy bills as an extra advantage. The extra warmth in your home will help to turn any excess moisture into steam which can then be removed easily by ventilation. In terms of exterior causes of mould, you should regularly check the outside of your property. Make sure your gutters are intact, free from moisture, and at the correct angle to allow water to drain away. Dripping or overflowing gutters can direct rain water onto the exterior walls of your home, which can then penetrate through to affect the structure. If there are any cracks in walls, missing roof tiles, or signs of damp then make sure you get it fixed as soon as possible. Once moisture finds its way into your walls and flooring you might not notice the problem until irreparable damage is done.
More recently, builders have begun to use damp proof layers in the initial stages of a buildings construction. Most new builds will have a damp proof membrane (see right) and a damp proof course. A DPM is placed under the floor between the substrate and a layer of protective sand, and a DPC in the walls. The DPM is usually a polythene layer and aims to prevent moisture rising from under the building and affecting the flooring. Although you’re probably not considering building a house any time soon, you may consider building a garage or outhouse, in which you may choose to put a layer of protective DPM. There are 2 industry standard units used to measure the thickness of polythene, gauge and microns (Mu). The higher the gauge or microns, the thicker the polythene is and the more durable and strong it should be. For a Damp Proof Membrane I’d recommend using polythene that’s at least 1000 gauge or 250Mu. Any less and you risk puncturing it during the construction stages, rendering it useless. Make sure you purchase a product that’s labelled as a damp proof membrane or one that clearly states that it’s waterproof, and purchase from a reputable supplier.
The damp proof membrane should be completely sealed to the DPC in the walls to ensure its effectiveness, and this is perhaps the most crucial stage of the process. Unless you have prior experience in damp proofing, I’d recommend using a trained professional to undertake this task. It’s a tricky time consuming job that involves specialist equipment, and the slightest mistake could have disastrous consequences once construction is completed. If you insist on undertaking the work yourself, don’t be afraid of consulting a professional beforehand. Most are more than happy to offer a few friendly words of advice.