Roof waterproofing surface curling

 November 23, 2020. 2:54 PM

Polymer bitumen membranes applied with traditional methods (propane gas flame torch) can be applied in different ways, depending on the surface they need to be applied to.
These surfaces can be:

  • “totally free” (independent laying)
  • “Partial laying” or partially glued parzialmente al supporto;
  • “Total adherence laying” (all surfaces).

In all three cases both the overlap and the perimeter of the covering are soldered to the support. Depending on the type of laying used the membrane will be more or less free to move for any eventual temperature or insulating system changes etc.

1. Is a certain amount of cover movement normal?
In summer and winter, as during the day and at night, a certain amount of movement is normal due to temperature change. Movement generally occurs near the corners of the building, since these are the critical areas where the movement converges.

2. How do non-soldered membranes move?
Completely supported non-soldered membranes tend to move in opposing diagonal corners.

3. What can happen if the membrane has not been properly laid?
Bitumen polymer membranes reinforced with non-woven polyester have a 50% stretching to breaking point. Therefore it is difficult to imagine a membrane breaking but an end lap could come away if it has not been installed properly.

4. What can new buildings do to membranes?
Where new constructions are concerned the settling movement of the buildings can cause abnormal tension to the roofing cover.

5. What is it that moves frequently?
Quite often it is not necessarily the waterproof cover which moves, it is the insulating panel under it. Relatively low temperatures (70°C) can create dimensional stability problems for some insulation. Therefore it is necessary to check both the presence and the perfect hold of the mechanical fixings (on average 4 per m²).