Preparing a deck for torch-down roofing involves ensuring the surface is solid, flat, and free of anything that could cause damage during the installation. The sheathing should be in good condition—typically plywood or OSB of at least ½ inch thickness—securely fastened to the underlying structure. Any damaged, rotten, or warped boards need to be replaced to avoid future problems. Fastening is critical; nails or screws should be spaced properly, usually every 6 to 8 inches along edges and every 12 inches in the field, to prevent movement or squeaking when the membrane is heated. Before starting, check the flatness carefully. Use a straightedge or level to find dips or bumps exceeding 1/8 inch in 10 feet, as uneven surfaces can cause poor adhesion or pooling water once the torch-down is applied. Minor irregularities can sometimes be smoothed with a leveling compound designed for roofing purposes, but significant unevenness requires more extensive repairs or sheathing replacement.
If you’re doing a DIY inspection before calling a pro, walk the deck and look for soft spots by pressing with your foot or a tool; these might indicate compromised sheathing. Also, check nail pops or loose boards that you can mark and tighten. It’s important to remove any debris, old roofing materials, or protruding fasteners since these can interfere with the torch-down membrane. However, torch-down application itself is best left to experienced roofers because it involves an open flame and specialized techniques to avoid fire hazards and ensure proper bonding. When you contact a contractor, ask specifically about their experience with torch-down on wood decks and how they address flatness issues during preparation. Also, inquire about how they ensure the fasteners won’t damage the membrane or cause leaks down the road. These questions help confirm their understanding of this sensitive preparation process and their commitment to a durable, code-compliant installation.