Flat roofs are known to be problematic. This can either be the result of poor workmanship, poor maintenance by the home owner or simply the roof has exceeded it's life.
When it comes to renew your flat roof, trying to decide on which product and contractor to use can be daunting, especially with such a wide variety of systems available on the market.
Although there are varients of each, there are typically 2 different types of flat roof:
BUR (Built-Up Roof)
A hot tar and gravel system, using multiple layers of felt/ bitumen sheet, traditionally ballasted with a layer of gravel on top.
While this style of flat roof is the most common it is also the most problematic. This again can come down to poor workmanship but the most obvious reason for a felt roof to fail is that it has joins/ overlaps. Any join on a felt roof is vulnerable to leaks, especially if there is ponding. BUR are also particularly vulnerable to thermal expansion, which results in splits and cracks. If water is trapped between the layers and freezes in the winter months, this is forcing the material to expand and results in more problems.
I have also found in my experience that the weight of a ballasted felt roof can cause structural problems. A ballasted roof is very heavy, even more so if there is trapped water between the layers and this can cause structural joists to sag and bow. This can create ponding which leads to leaks etc.
BUR are applied using flame torches and extreme heat. If not used properly, this could lead to a fire on the roof or underlying structure.
Single ply roofs typically comprise of a sheet membrane being applied onto the roof deck. This can be either a plastic or rubber sheet that comes pre-made on a roll, or a liquid applied system (GRP or Polyurethane) that is chemically bonded to the roof deck.
Guarantees on these systems vary but most offer between 15- 25 years against the failure of the membrane.
Plastic or rubber sheet roofs require heat welded joints to hold the roof together whereas liquid roofs have no visible joins.
Single ply roofs are an excellent method of waterproofing if installed correctly. Not all suppliers require the installers to be trained to use their product and consequently the industry suffers from poor workmanship. This can give Single Ply roofing a bad name. If installed correctly however, a single ply roof will perform exceptionally well under all conditions and is an extremely cost effective way of keeping your flat roof watertight, permanently.