Preparing a deck for TPO (Thermoplastic Polyolefin) roofing involves ensuring that the surface is clean, structurally sound, and flat to promote proper installation and longevity. The sheathing must be secure, dry, and free of any damage such as rot or warping. Common decking materials include plywood or OSB (oriented strand board), typically 1/2 inch or thicker. The surface should be fastened with corrosion-resistant screws or nails spaced according to local building codes and manufacturer recommendations, usually 6 to 8 inches apart along the edges and 12 inches in the field. Fasteners must be driven flush or slightly countersunk without damaging the sheathing layers. A flat surface is essential because TPO membranes are thin and flexible but can easily show imperfections that may lead to ponding or wrinkling. Use a long straightedge or a level to check for bumps, depressions, or ridges. Any unevenness greater than 1/8 inch over 10 feet should be corrected by sanding, adding a leveling compound, or replacing damaged sheathing panels before installing the membrane.
To perform a safe DIY check, walk the deck carefully to see if any nails or fasteners are loose, protruding, or rusting, as these issues can cause punctures or tears in the TPO. Additionally, visually inspect the entire deck surface for any signs of moisture damage. Avoid using power tools or aggressive cleaners that could damage the sheathing. If the deck feels spongy or bouncy, it could indicate structural issues requiring professional repair. When calling a roofer, ask if they will inspect the decking moisture content and structural integrity before installation, as well as what sheathing type they recommend for your specific deck. You might also ask how they ensure deck flatness and fastener placement meet warranty requirements, reducing risks of leaks or membrane damage. Understanding these details helps protect your investment and ensures a long-lasting roofing system.