Waterproofing Membrane for Green Roof

Sarnafil PVC Membrane for Green RoofPreparation of Substrate

1.       Base concrete substrate must be free from all projections and depressions. The surface must be reasonably smooth and leveled to the required gradient as designed for.

2.       The area must be free from dust, debris, oil and other contamination. All cracks, pot holes and honeycomb are to be made good prior to the waterproofing application.

3.       The substrate to be covered with screed shall be well wetted before the application of screed..

Sarnafil G 476-12 Green Roof System

4.       Unroll Sarnafil G 476-12, fiberglass reinforced PVC waterproofing membrane, loosely laid over the substrate or separation layer and hot air welded on the overlap 80mm wide, making sure that the overlap area must be clean and dry.

5.       For hand welding, use the Leister Triac hand welder, 40mm wide nozzle for straight weld and 20mm wide nozzle for corners and detail work. The three stages are:-

  • Spot weld the overlap.
  • Pre-weld: Weld the rear overlap area so that a 35mm opening remains for the finishing weld.
  • Final weld: Sarnafil PVC hand roller should be guided at a distance of 30mm parallel to the air outlet of the welding nozzle. Always roll the hand roller fully across the seam.

6.       Testing of welded seams:-

  • Visual seam check: Shiny surface and even quality of welding beads.
  • Mechanical seam check: Use a screwdriver to slide along the welded seams to check for voids and any welding defect.
  • Peeling test: At the overlapped cut the membrane into 50mm width strip and firmly peel it. Tearing point should be located beyond the effective welding seam.

7.       For perimeter fixation around the parapet wall, Sarnafil G 476-12 membrane must be secured with Sarnafil U bars and PVC welding cord against tearing and peeling off by wind uplift. Perimeter fixation shall not be required when the garden built-up is above 300mm thick.

Upstands, Flashings & Roof Details

8.       Followed by the upturn membrane, Sarnafil G 476-12 hot-air welded overlap 40mm covering the Sarnafil U bars and fully adhered to the parapet wall with Sarnafil approved adhesive.

9.       Sarnafil G 476-12 can be terminated with metal strip fastened through the membrane and sealed with an approved sealant at a height at least 150mm. Or alternatively, make a groove line by saw cutting on the required height and tucked in with Sarnametal sheet (PVC coated) where the upturn membrane Sarnafil G 476-12 can be welded on it.

10.   For corners, vent pipes, drains and other roof details, please refer to Sarnafil installation handbook procedures.

Water Ponding Test

11.   Carry out flood test 48 hours minimum after completion of the waterproofing works. Restrict water run-off from membrane area by plugging drains and creating dams or dikes. Flood restricted area to depth of about 100 mm and maintain at this depth for 48 hours. Any punctured or defective areas shall be made good by an approved method and retested.

12.   The membrane shall be cleaned and inspected before proceeding with the remaining built-up protection measure.