Flat roofs can be problematic as they are horizontal and can allow water to stand which is fine, if they do not leak. Traditionally, the construction of a flat roof was tar and gravel with a slight gradient to allow water to drain off. However, this method can fail in cold climates due to ice build up at the point of drainage, water can pool on the flat roof, allowing penetration and causing a leakage into the room below. Flat roofs are often the favoured method of roofing an extension where a pitched roof may not fit the profile of the property.
More modern construction methods of repairing or renewing a flat roof are the usage of a liquid rubber or rubber membranes or waterproof felt materials and bitumen laid over a concrete screed. Membranes can also be made of polyester reinforced PVC Liquid rubber, polyisobutylene (PIB) synthetic rubber and polyvinyl chloride (PVC) which is a thermoplastic polymer.
One advantage of a liquid based material is that it can penetrate into cracks in the concrete and help prevent leakage. This can be used in flat roof repairs or in the construction of a complete new roof. The main disadvantage is that the roof must not have a gradient or the liquid will run off or become uneven, leaving areas of the roof with no protection. Liquids can provide a barrier which is both flexible and seamless when applied correctly and can come in a range of colours to complement your property and its surroundings.
A disadvantage of the application of felt materials and rolls of rubber membranes are that they may leave vulnerable areas where the edges of the sheets meet if they are not sealed correctly. Some single-ply roofing is an impervious membrane which is self sealing, requiring no hot sealant therefore reducing the risk of accidents as well as ensuring watertight joints.
All materials used when installing flat roof must be environmentally friendly and meet the current building regulations. Materials must be weatherproof, be resistant to ultra-violet radiation and maintain their physical properties under a wide range of temperatures. Some flat roofs are tiled on top of the sealants and are used as barbecue areas or gardens, especially in urban areas.
Whether you are installing a new flat roof or carrying out roofing repairs, the main consideration is to ensure that it is watertight or the joists and underlying construction of the whole roof may be compromised. Another consideration is that the work must be able to withstand the rigours of the climate for years to come. If you are doing the work yourself, by using a roofing material which is recommended by the building trade, you will minimise the risk of leaks in your flat roof, thereby causing future problems. A reputable roofing contractor will always use approved roofing materials when constructing your flat roof, meet all the current building regulations and give a guarantee of workmanship.