This is the Method Statement for the Application of Sarnafil G 476-15 PVC Waterproofing Membrane for Green Roof Garden.
Preparation 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.
Cement and Sand Screed
4. The cement and sand screed shall be site mixed at ratio of 1:3 with approved waterproofing compound at recommended dosage from the manufacturer.
5. The mixture screed will then be laid to fall (50mm thick) and steel trowel to the required gradient finish.
6. Create cement and sand (1:3) fillet at base.
7. Depending on the substrate surface, a leveling or separation layer may be required, such as geotextile/ felt 130g/m2, loosely laid with 80mm wide overlap.
Sarnafil G 476-15 Green Roof System
8. Unroll Sarnafil G 476-15, 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.
9. 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.
10. 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.
11. For perimeter fixation around the parapet wall, Sarnafil G 476-15 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
12. Followed by the upturn membrane, Sarnafil G 476-15 hot-air welded overlap 40mm covering the Sarnafil U bars and fully adhered to the parapet wall with Sarnafil approved adhesive.
13. Sarnafil G 476-15 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 476-15 can be welded on it.
14. For corners, vent pipes, drains and other roof details, please refer to Sarnafil installation handbook procedures.
Water Ponding Test
15. 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.
16. The membrane shall be cleaned and inspected before proceeding with the remaining built-up protection measure.
Drainage Cell, Growth Media and Vegetation Built-up
17. Loose lay the Moisture retention/ Protection mat, traversing the width of the designated area and allow 100mm overlap.
18. Then, loose lay the Drainage and Reservoir Panel/ Drainage cell over the underlying support surface (Retention Mat), close butted with adjacent sheet. Excess materials shall be trimmed by a heavy-duty cutter.
19. Place the Filter Sheet loose laid with a 20mm fold-up/ down margin all-round in excess of the planting area, covering the underlying drainage panel. Allow 100mm overlap in uni-directional throughout the designated area.
20. Growth media and vegetation will be incorporated by others.
The information contained herein and any other advice are given in good faith based on Sika’s current knowledge and experience of the products when properly stored, handled and applied under normal conditions in accordance with Sika’s recommendations. The information only applies to the application(s) and product(s) expressly referred to herein and is based on laboratory tests which do not replace practical tests. In case of changes in the parameters of the application, such as changes in substrates etc., or incase of a different application, consult Sika’s Technical Service prior to using Sika products. The information contained herein does not relieve the user of the products from testing them for the intended application and purpose. All orders are accepted subject to our current terms of sale and delivery. Users must always refer to the most recent issue of the local Product Data Sheet for the product concerned, copies of which will be supplied on request.