Laying with adhesives

When using adhesives, all layers of the roof structure must bond to one another. Hot bitumen, cold bitumen and polyurethane adhesives are used. When selecting an adhesive, the purpose should be determined and the SCHEDETAL instructions observed. For adhesive bonding to a suitably prepared base, roofing membranes with a synthetic non-woven or glass non-woven underside layer are to be used. The non-woven lamination and the base have to be dry before bonding. The membranes should overlap by at least 5 cm (observe section 8.2.1). Since the membrane seams are welded using hot air, the welding area must be free of adhesives. If modernising, adhesive bonding is only possible if adhesion of the old roof structure to the supporting base and existing roof seal can be ensured.

Strip bonding with SCHEDETAL roofing membrane adhesive

The roofing membrane adhesive is applied to the prepared surface strip by strip. Manufacturer requirements are valid in regard to the base (SCHEDETAL adhesive for roofing membranes PUR 6.0 kg, application: 250-300 g/m2). If employing trapezoidal steel profiles or newly delivered metal sheets, the base should be examined accordingly to ensure proper adhesion of the layered roof structure (use primer if necessary). The amount of adhesive needed generally depends on the suction calculated according to DIN 1055, part 4, and is specified by the adhesive manufacturer. In the central region of the roof, three or four strips of adhesive are applied per metre of width. More adhesive is required around edges and in corners. The adhesive is applied using a suitable tool or by hand (around domelights, ventilation units, etc.). At least one strip of adhesive must be applied to each upper corrugation on trapezoidal steel profiles. Roofing membranes with an additional synthetic or glass nonwoven layer on the underside are rolled on to the viscous adhesive and properly pressed down. Observe the adhesive manufacturer?s technical specifications. Prepare areas for bonding only if they can be sealed within 5-10 minutes. Repositioning of the membrane is normally possible for up to 15 minutes. The surface sealing is firmly anchored to the supporting base at the edge of the roof and at junctions and borders.

Please note: since the adhesive does not bond strongly at first, ballast should be used to secure the membranes against wind uplift.

Full-area adhesive bonding with bitumen: it?s only possible with ExtruBit

ExtruBit roofing membranes with an additional synthetic or glass non-woven layer on the underside can be bonded with hot bitumen (full or partial surface application). Additional measures may be necessary with roof gradients (see flat roof guidelines). The temperature of the bitumen adhesive should not exceed 185°C at the area of application. The kind of bitumen used depends on the roof incline. Here, a low-solvent, polymermodified bitumen can be employed. Follow the manufacturer?s instructions for amount and method of application.

a) Flame melting method
The hot bitumen is poured on to the base and evenly spread using sliders. After the hot bitumen has cooled off, the membranes are rolled out halfway, aligned and rolled back again. The cooled layer of bitumen (but not the ExtruBit membrane) is melted to a sticky or liquid state over the entire width of the membrane using gas burners, and the membranes are rolled into this adhesive bed, ensuring no air bubbles are formed.

b) Brush application method
The hot bitumen is poured on to the base and evenly spread using sliders. After the hot bitumen has cooled off, the membranes are rolled out halfway, aligned and rolled back again. The cooled layer of bitumen (but not the ExtruBit membrane) is melted to a sticky or liquid state over the entire width of the membrane using gas burners, and the membranes are rolled into this adhesive bed, ensuring no air bubbles are formed.