Flat Roofing

A flat roof may be just what you're looking for. Though not architecturally logical, since wet weather will roll off quicker from a sloped roof. Yet for historic Modern-style buildings, flat roofs are at the core of the architecture, meant to reflect the broad horizontal lines of the natural landscape. Of course, you don't need to live in a modern house to deal with a flat roof. Traditional homes often have sections of flat roof over shed dormers, above porches and garages, and on balconies. And their horizontal lines abound in the West and in urban areas. But flat roofs take a pounding from harsh weather, which is why they rarely last as long as a good sloped roof. Fortunately, modern materials for covering flat roofs have improved considerably over the past two decades; some carry warranties of up to 20 years, approaching those for sloped roofing.

A flat roof is almost level in contrast to the many types of shaped roofs. The slope of a roof is properly known as its pitch and flat roofs have up to approximately 10>∞>.[1] Flat roofs are an ancient form mostly used in arid climates and allow the roof space to be used as a living space or a living roof. Flat roofs exist all over the world and each area has its own tradition or preference for materials used. In warmer climes where rainfall is less likely and freezing is unlikely to occur, many flat roofs are simply built of masonry or concrete and this is good at keeping out the heat of the sun and cheap and easy to build where timber is not readily available

Any sheet of material used to cover a flat or low-pitched roof is usually known as a membrane and the primary purpose of these membranes is to waterproof the roof area. Materials that cover flat roofs typically allow the water to run off from a slight inclination or camber into a gutter system. Water from some flat roofs such as on garden sheds sometimes flows freely off the edge of a roof, though gutter systems are an advantage in keeping both walls and foundations dry. Gutters on smaller roofs often lead water directly onto the ground, or better, into a specially made soak away. Gutters on larger roofs usually lead water into the rainwater drainage system of any built up area. Occasionally, however, flat roofs are designed to collect water in a pool, usually for aesthetic purposes, or for rainwater buffering.

Traditionally most flat roofs in the western world make use of tar or more usually tar paper applied over roof decking to keep a building watertight. The tar or tarpaper is in turn covered in gravel to keep the sun's heat, UV rays and weather off it and helps protect it from cracking or blistering and degradation. A main reason for failure of these traditional roofs is ignorance or lack of maintenance where people or events cause the gravel to be moved or removed from the tar or tarpaper waterproofing, thus exposing it to weather and sun whereupon cracking and blistering occurs over time and eventually water gets in. Tarpaper is usually a material soaked or impregnated in tar. As gravel cannot protect tarpaper surfaces where they rise vertically from the roof such as on parapet walls or up stands, tarpaper variants are produced with fine gravel applied to the hot tar during the process of manufacture such that a permanent layer of gravel is stuck to it in order to give it ongoing protection. Tarpapers vary in quality as does the workmanship and training of those applying it to produce more or less successful results. In some microclimates or shaded areas these rather 'basic' tarpaper roofs can last well in relation to the cost of materials purchase and cost of laying them. The cost of modern membranes has come down over recent years to make them more affordable. There are now more firms supplying modern alternatives and there is generally a growing awareness of their performance and availability.

If a leak does occur on a flat roof, damage often goes unnoticed for considerable time as water penetrates and soaks the decking and any insulation and/or structure beneath. This can lead to expensive damage from the rot which often develops and if left unrepaired can weaken the roof structure. There are also various health risks to people and animals breathing the mold spores: the severity of this health risk remains a debated point.

Another problem with maintaining flat roofs is that if water does penetrate the barrier covering (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 seen. Thus it is not easy to find the source of the leak in order to repair it. Once underlying roof decking is soaked, it often sags, creating more room for water to accumulate and further worsening the problem.

Another common reason for failure of flat roofs is a lack of drain maintenance where gravel, leaves and debris block water outlets (be they spigots, drains, downpipes or gutters). This causes a pressure head of water (the deeper the water, the greater the pressure), which can force more water into the smallest hole or crack. In colder climates, puddling water can freeze, breaking up the roof surface as the ice expands.

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