I’m no roofer or technical manager, but I often have the privilege of hanging around some of the best in the industry. Here are some of their tips for the initial stages of a TPO (thermoplastic polyolefin) single-ply roofing membrane installation. As always, the specific manufacturer’s installation instructions supersede any advice given here.
1. Factory-installed plastic wrapping is not designed as protective covering for insulation materials and should be removed. Use “breathable” type covers such as canvas tarpaulins to allow venting and protection from weather and moisture.
2. Because colored TPO membranes may exhibit different welding characteristics, contact the roofing manufacturer before attempting to weld different colored TPO membranes with white membranes or flashings.
3. Confirm the adequacy of the new roofing system to provide positive slope to drain. Eliminate ponding areas by the addition of drainage locations or by providing additional pitch to the roof surface.
4. Confirm that the height of equipment supports will allow the installation of full-height flashings.
5. It is strongly recommended that the building owner have a moisture survey performed to ascertain the condition and suitability of the existing roofing materials to receive a TPO recover system. A survey is usually required if perlite or wood fiber insulation is used in a recover system.
6. When installing new nailers, secure shim material simultaneously with overlying solid wood nailers. Shim material should be continuous; spaced shims should not be used.
7. An air retarder is usually required where large wall openings greater than 10 percent of the total wall area can be open during a wind storm, including opening due to storm damage. Refer to Factory Mutual Loss Prevention Data Sheets 1-28 and 1-29 for specific installation procedures on air retarders.
8. When installing crickets, saddles or cut tapered insulation panels, it may be advantageous to use low rise foam adhesive in lieu of mechanical attachment.
9. Adhesive beads must be evenly spaced at the rate required for the insulation board size and type of roofing system being installed.
10. Install the TPO membrane so that the laps run across the roof slope lapped toward drainage points. On metal decking, install sheets perpendicular to deck direction so that fasteners will penetrate the top flanges and not the flutes; however, there will be limited areas of the roof (i.e., perimeter areas) where this is not practical.
11. If the deck is running opposite the slope of the roof (flutes running horizontally), then the membrane should run ridge-to-gutter to ensure proper fastening to the top flanges of the deck.
In our next blog, we’ll take a look at TPO mechanically attached membrane securement and field seaming.
