When installing the membrane and the underlying roof covering, it should be done “the sooner the better”. In fact, the membrane should not “last” without covering. That is why we do not specify the parameter “UV resistance” on the product labels, and in the installation manual you will find the recommendation “install immediately”.
Roof membranes are made from polypropylene (PP) and are not resistant to UV. UV daylight destroys the chemical bonds of PP – degradation occurs, the material loses its durability parameters, and as a result cracks and ceases to be fully waterproof
This is why UV stabilisers, which are chemical compounds that increase resistance to the damaging effects of ultraviolet radiation, are used in membranes. The stabilisers act as shields that cover the polypropylene bonds. But when a particle of radiation energy falls on the shield, the shield “burns out”. The longer the radiation exposure, the more shields disappear and fewer and fewer bonds are protected. If we prolong the installation of the base covering, the membrane lying on the roof becomes less and less resistant to UV.
The “UV resistance” parameter is given in months, e.g., 3. It might be misread as the period that can elapse between the installation of the membrane and the laying of the roof tiles. It should be remembered that after 3 months, the membrane will already have considerably fewer stabilisers. In addition, depending on the time of year, the intensity of UV varies. This means that a membrane installed without tiles for 3 months in winter will be in much better condition than in summer. The UV intensity level in the different months is shown in the table below:
Therefore, we strongly recommend installing other elements as soon as possible. It is best to position the site of works so that when the roof membrane is installed, the tile is already waiting on the job site.