How to: Hot-Air Welding of Flat Roof Membranes

• Rule no. 1: weld like with like. Be sure both pieces of material have the same composition. Two differing sheets of material cannot be strongly welded together.
• Welding surfaces must be dry and free from contaminants such as dust and dirt.
• Carry out test welds and perform peel tests to ensure the correct temperature/pressure/speed settings are used. See our how-to article on roofing membrane test welds. 
• Always check the hot-air welding device before using. Check for blocked nozzles, for defective heating elements, and in case the filter requires cleaning.

Manual Welding Process

1. Stitching the overlap

2. Pre-welding

3. Final welding

The distance between the pressure roller and the nozzle opening should be between 20 and 30 mm to ensure that the weld seam is joined as efficiently as possible. The pressure roller must be guided so that it is parallel to the nozzle. This will ensure that the welding process yields the best possible results (see images above).
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​The hot-air nozzle should be cleaned periodically to keep the contaminants out of the welding seam. A blocked nozzle will restrict the tool’s air output which may cause fluctuations in the output temperature.