Initially, I should be precise and say that flat roofs as such do not exist. Under the term “roofs”, roofs with slopes of less than 15% (flat roofs with large slopes) are considered, and larger than the minimum required for unhindered drainage, of 0.5%. Although this mostly depends on the type of flat roof, it is said that its average lifetime should be at least 10 years. However, in order for a flat roof to meet the basic purpose, it is necessary to keep control and maintenance on a regular basis.
Flat roofs can be grouped according to materials and method of manufacture. Here one basic division is given, and the types of roofs are given in the growing order according to the durability, but also according to the construction costs:
Asphalt level roofs
The flat asphalt roof has been used since the 1890s and most often consists of one layer of asphalt compound applied to the roof plate, which is usually a layer of mineral granulate.
With fewer repairs, the lifetime of this type of flat roof is about ten years.
Flat roofs with one-layer membrane
One-layer membrane is the latest type of flat roof solution and is often used instead of existing multilayer membranes. There are many types of membranes on the market. The installation of the membrane depends on the material in different ways, and the usual guarantee ranges from 10 to 12 years. The installation itself is also very important for leakproofness and continued maintenance.
Multilayered flat roofs
Multilayer flat roofs consist of several alternately laid layers of linen or paper coated with layers of bitumen, above which comes a layer of granules, or ballast.
The granulate has the task of protecting the inner layers from moisture and is bonded to the asphalt mixture. It is predicted that these roofs last for 10 to 30 years. However, since the granulate covers, the membrane, inspection, and maintenance of the roof itself are more difficult.
Flat roofs of flat or profiled sheet metal
They can last for decades, of course, depending on the quality of the material used, the way it is maintained and exposed to atmospheric conditions. Metal surfaces require regular painting, so today copper and stainless steel are often used, especially for surfaces that are hardly accessible for maintenance. In the case of metal roofs, a very important element is thermal insulation, which can be between two layers of sheet metal, in the so-called sandwich panels, or as a separate layer.