As an architect or planner of a flat roof or an industrial roof you have many possibilities for design. But for the right sealing against all strains, there has to be a fitting material choice for the perfect roof.
The roofer calculates the right material based on several categories due to DIN 18531 as well as the norm for each material.
The right material choice for the sealing is crucial for the preservation of the structure of a building with a flat roof. During calculation of the of the material the roofer has to determine the strain category. Is it a standard execution for the usual requirements or is a higher requirement necessary (for example for skyscrapers).
Every sealing material has to be waterproofed, stable, flexible and tear proofed under the maximum and minimum conditions of the expected temperature, under deformation or wind load.
Furthermore, you must consider if a roof sheeting is set for greening, for gravel or simply exposed. The chemical and biological strains are to be considered as well as the mechanical and thermal ones.
The type of sealing depends also on the roof structure (ventilated or not) as well as the substructure. An important factor is next to the strains the usage of the building.
The age process is speeded-up by certain influences with the result of lower durability of the sealing.
Biological influences are alkaline substances, algae infestation and microbes’ influences. Moreover, can a long-term water accumulation with high temperatures lead to a breach of inferior material.
Because of that, you should only use proofed/ standardized material, that was exposed over a longer period of time to the extremes and is still functioning afterwards.
The chemical influences are acidic substances (bird dung, leaves, pollen or acid rain), that are acting on the sealing. Grease and oil are found in a higher concentration at industrial buildings due to the exhaust air. They have next to waste gas form the nearby traffic a negative effect on the sealing.
In this case the bitumen sealing is not advised, since bitumen is not resistant against related, mineral oil based greases and oils as well as fuel (gasoline or diesel) and some organic solvents.
For a long durability of the sealing the sheeting has to withstand thermal interaction such as UV-radiation, high and low temperatures, rain and hail or ozone. The material has to be chosen regarding to the fact, if there is a surface protection or not.
The mechanical influence is given if the support structure is exposed to movement, such as formwork made of wood, soft insulation or a greening. The sealing has to withstand shock loads and severe weather.
For every roof there has to be determined individually what kind of sealing method is used. The sealing has to comply with the standards and the product datasheet from the rulebook of the roofer’s guild. If there are used combinations of materials, their compatibility has to be ensured.
Sheeting can be made of bitumen, synthetic material or rubber.
Penetrations such as drains, outlet vents, light domes or chimneys weaken the sealing quality and have to be planned very carefully. The number of penetrations should be reduced to a minimum, for example by condensing lines. The penetrations have to be sealed with a special material. Most of the manufacturers of sealing material offer supplies for that matter.
The sealing of green rooftops must show resistance against vegetation-related damage to the sheeting. If you haven’t planned a green roof but have gravel on top, it is advised to use root resistance sealing, because of the flight of pollen that can start a vegetation in the gravel.
The material for the sealing of industrial buildings (walls and roofs) have to be matched to the production inside. Outlet vents can transport substances (grease, oil) to the sealing. For example, the industrial kitchen produces a lot of grease and oil that reaches into the joints, cracks and outlet vents and can cause damage to some materials (like bitumen).
There has to be an individual consideration of the strains, the sealing has to undergo. The material is to be chosen accordingly.