This is the Method Statement for the Application of Sarnafil S 327-12 PVC Waterproofing Membrane.
Installation of Thermal Insulation Boards and Vapour Control Layer
- Lay the vapour control layer (PE film) over the structural metal decks (Galvanized cold-rolled steel with minimum thickness 0.8mm).
- When used, vapour control layer (PE film) must be sealed with PE film tape at all overlaps by 100mm, to perimeters and around penetrations to achieve airtight bond.
- Placed thermal insulation boards (100mm thick Rockwool with minimum density 175kg/m3) and secured with thermal insulation washer and Sarnafil BD fasteners screwed to the steel deck according to the thermal insulation manufacturer’s requirements.
- Thermal insulation boards are lap spliced, creating a continuous insulation layer with no thermal bridging.
Sarnafil S 327-12 mechanically fastened using Sarnafast System
- Unroll Sarnafil S 327-12, polyester scrim reinforced PVC waterproofing membrane perpendicular to the metal deck direction and mechanically fastened the overlap with Sarnafil fastening components (membrane washers and fasteners).
- Install KTL membrane washers (barbed metal plate) and fasteners BD, centered along the 30mm line traced on the membrane. The top of the washer should be even with the top of the membrane.
- Only one fastener is to be installed into the top flute of the steel deck. The fastener must penetrate the steel deck by a minimum of 20mm (Minimum fastener length = Whole roof build-up + 20mm). Fastener spacing is to be in accordance to the project specific calculations made by Sarnafil and the fixation pattern must always be symmetrical (i.e. every flange, or every second flange, etc.)
- Install adjacent sheets along the lap lines marked on the membrane (120mm from the sheet edge).
Hot-air Welding Procedures
- When hot air welding of Sarnafil membrane, the overlap area must be clean and dry. For straight seam welding (overlap is 120mm), Sarnamatic automated welding machine must always be use.
- For hand welding, use the Leister Triac hand welder, 40mm wide nozzle for straight weld and 20mm wide nozzle for 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.
- 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.
- For perimeter fixation around the roof edge or near the parapet wall, Sarnafil S 327-12 membrane must be secured with Sarnafil U bars and PVC welding cord against tearing and peeling off by wind uplift.
Upstands, Flashings & Roof Details
- Followed by the upturn membrane, Sarnafil G 410-12, hot-air weld overlap 40mm with Sarnafil S 327-12, covering the Sarnafil U bars and fully adhered to the parapet wall with Sarnafil approved adhesive.
- Sarnafil G 410-12 is terminated with metal strip fastened through the membrane and sealed with an approved sealant at a height at least 150mm.
- For corners, vent pipes, drains and other roof details, please refer to Sarnafil installation handbook procedures.
Water Ponding Test
- 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.