Know what you use!
When planning a roof waterproofing with bitumen, one should, as with any other material, have detailed knowledge of the material so that it can be used successfully.
Bitumen membranes have a long tradition but leave a lot to be desired in terms of sustainability, ergonomics, and efficiency.
In the following, we explain some points that should be taken into account during planning.
Bitumen roofing membranes do not like moisture.
A common problem with bitumen membranes is the presence of standing water.
On slope-free waterproofing, it accelerates the chemical and biological degradation of the bitumen roofing membrane.
The resulting corrosion processes can cause the bitumen roof surfaces to release acidic water.
In this case, a groundwater-neutral material such as aluminium should always be preferred.
Standing water also physically damages the bitumen roof through wet-dry zones in summer and frozen areas in winter.
Therefore, to prevent ice breakage, sloping layers can be installed in an elaborate way to lead to surface water run-off.
If this is not possible, the flat roof guidelines provide for special constructions such as reinforced roof waterproofing to compensate for the higher load of standing water.
In this case, a renovation solution is more sensible, efficient, and economical.
There are ways to turn leaking flat roofs into cost-effective, safe, and virtually maintenance-free roofs without expensive demolition and disposal costs.
Diffusion? Non-existent!
What has also often been seen on bitumen roofing membranes is blistering.
Blisters are caused by dirt, gravel pressure or residues of mineral layers that could not be completely removed from the roofing.
When a new bitumen membrane is bonded to the old roofing, the moisture contained in between cannot escape and this also inevitably leads to blistering.
Roof covering systems that are open to convection on the outside prevent these effects, because moisture (e.g. day water during construction) is not trapped between two impermeable layers but can escape.
Another related problem is that the installations carried out in the course of the renovation work on the bituminous membrane cannot, for the most part, be carried out without penetration, thus possibly creating thermal and sound bridges.
Here, a modular system, on which accessories such as steps, walkways or snow rails can easily be installed without penetration, could be the better choice.
Even PV systems can be retrofitted, taking the statics into account.
On fire for bitumen roofing membrane?
Gas burners with an open flame are often used to weld classic polymer bitumen roofing membranes. Temperatures of up to 1,000 °C occur.
According to the technical information of the DUD (Industrieverband Kunststoff-Dach- und Dichtungsbahnen e.V.), the risk of ignition of flammable roofing materials – such as wood and insulating materials – is many times higher.
In addition, if the internal polyester fleece is heated too much, the membrane will break at the most heated point, i.e. in the seam area, when the substrate contracts later.
The bitumen roof itself can also ignite due to overheating.
Therefore, at the beginning of the planning process, it is advisable to choose a non-combustible material that is optimised against flying sparks and radiant heat, preferably in combination with non-combustible insulation that is laid without an open flame.
Deconstruction after the period of use is also rather difficult.
Due to the many different chemical and mineral components, bitumen roof sealants are classified as hazardous waste and therefore have no residual value.
1 kg of bitumen is equivalent to approx. 1 litre of heating oil. In addition, two layers of bitumen sheeting weigh approx. 10 kg/m2, which equals 10 litres of heating oil/m2.
It works better. And easier. And more flexible.
Nowadays, when planning a roof construction project, there is no way to avoid looking at alternative materials and systems.
These have a significantly better environmental balance and are more resistant to biological, chemical and physical influences.
There are almost maintenance-free, modular systems that are far more advantageous in terms of building physics, as they allow diffusion and enable roof constructions free of thermal bridges.
This even increases the property value.
It is therefore best to rely on a product that has been tried and tested for decades and is known for its durability, quality and optimum price-performance ratio on more than 100 million square metres of installed roof.
Find the right solution with Kalzip!
