Traditionally most flat roofs in Ireland are constructed of plywood, concrete or metal and generally weatherproofed with either “torch-on” (bitumen based), synthetic membranes (PVC, TPO) or asphalt applied over roof decking to keep the building watertight. These materials should be UV stable (or have a protection layer) to slow the degradation process, average life expectancies should be at least 35 years for all systems. Flat roofing products vary in their quality, as does the workmanship of those applying them and care must be taken when selecting both – to ensure suitability and adequate service life.
A major problem with flat roofs, is that if water does penetrate the waterproof layer (be it traditional or a modern membrane) it can travel a long way before causing visible damage or leaking into a building where it can be actually seen. It is not easy to see where the roof is actually leaking in order to repair it. In our experience, once underlying roof deck insulation is soaked, it often sags causing a further collection or ponding of water in that area and the problem generally worsens.
Another common reason for failure of flat roofs is a lack of maintenance – whereby gravel, leaves and debris block water outlets, thus water cannot drain away and builds up. This causes a hydrostatic head of water (the deeper the water the greater the pressure) which can ‘push’ more water into the smallest hole or crack. Roof Survey always recommend an maintenance programme incorporating inspection/testing schedule’s of at least twice a year and always after big weather events.