Troubleshooting Flat Roof Welds: Air Bubbles in the Weld Seam

Rake nozzle and soft pressure roller for the Leister VARIMAT V2.

Growing insulation requirements have resulted in changes to roof structures in recent years. Rigid polyurethane (PUR), polyisocyanurate (PIR) or thicker mineral wool insulating materials with a higher level of compressive strength are now installed on the upper side of the roof deck. During the welding process, these insulating materials demonstrate virtually no elastic behavior resulting in a harder welding surface. This may cause air inclusions (bubbles) to form in the weld seam of mechanically fastened PVC roof sealing sheets under certain conditions, particularly if the roof substrate is uneven.
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The new rake nozzle kit from Leister ensures that all leak-tightness and aesthetic requirements are met even in roof structures of this nature. The rake nozzle provides constant pressure on the lower PVC sheet. The soft silicone pressure roller ensures the pressure is distributed as effectively as possible over uneven and hard substrates.

If you're having problems with air inclusions in your welds, contact us today for more details.