How is a bituminous underlayer mechanically fastened?

A bituminous underlayer is best installed as follows:

• The first membrane roll is unrolled and aligned.
• The membrane is mechanically fastened in the longitudinal overlap. The number of fasteners per running meter is determined based on the wind load on the roof.
  The fasteners are installed in a straight vertical line into the substrate and positioned on the marking within the overlap. The screws are placed 4 cm from the edge.
• The 12 cm overlap at the longitudinal seams and the 10 cm overlap at the end seams are welded together using a soft flame.

1. Overlap width: 12 cm
2. Screw distance from edge: 4 cm
3. Pressure plate distance
   from edge: ≤ 2 cm
4. Pressure plate width:
   4 cm
5. Roll marking indicates the screw locations
6. Underlayer finishing

For more information, see our guide: “All you need to know about the bituminous underlay”, available on the IKO website.