Preparing a deck for a green roof involves ensuring the surface is strong, even, and able to support the added weight of soil, plants, and moisture. The sheathing should be sturdy, ideally exterior-grade plywood or OSB, securely fastened to joists with corrosion-resistant screws or nails to prevent uplift or movement. The deck must be flat or have a slight slope, typically 1-2%, to aid water runoff and avoid pooling, which can damage the structure or cause rot. Before applying any green roof layers, inspect the sheathing for any signs of damage, rot, or loose fasteners and replace or tighten them as needed. You can perform a simple DIY flatness check using a long, straight 6-foot level or a string line stretched across the surface to spot high or low spots. Also, confirm the deck’s structural ratings meet local building codes for additional live and dead loads that green roofs impose, which is crucial for safety and maintaining warranties.
If you are unsure or spot unevenness beyond slight dips or warps, it’s best to call a roofing professional with experience in green roofs to evaluate the deck’s readiness and recommend corrective measures. Ask your contractor, “Is the current decking material suitable for a green roof, and will it hold up under the weight of saturated soil over time?” and “What fastening methods and corrosion-resistant materials do you recommend to ensure long-term durability and adherence to warranty requirements?” These questions help ensure your deck can support a green roof safely and maintain the integrity of the waterproof membrane beneath it. Proper preparation upfront prevents costly repairs down the road and helps you enjoy the benefits of a thriving green roof.