Removal

• Removing roof components and membrane. If there are any elements mounted on the plywood sheet or a membrane is laid over it, they must be removed before starting work.
• Inspecting damaged plywood: Check for moisture, brittleness, rot, or crumbling. Assess the extent of the damage and determine if replacement is necessary.

Preparation

• Trimming the sheet: Lay down the full plywood sheet, aligning it with one edge. Secure it with screws. Then use a chalk line to mark the cut, set the saw blade to the plywood thickness, and cut in place. If laying out the entire sheet isn’t possible on the roof, pre-cut the plywood to the required length on the ground.
• Cut openings in advance that won’t be accessible after installation — like those for refrigerator vents, antennas, and plumbing vent pipes.
• Cut down plumbing vent pipes flush with the surface so they don’t interfere with membrane installation or mesh application.
• Use a multitool to cut the remaining holes after the membrane or reinforced system is installed. Be sure to cover the RV interior with plastic to protect from dust and debris.
• Remove any nails or staples from the area where the new plywood will go. Clean the surface of dirt and dust before applying foam. An air blower may help.

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• Tip: You can ask Home Depot to pre-cut the plywood for convenience. </aside>

Installation

• Apply foam to the old plywood using a foam gun and “Gaps and Cracks” spray foam. Apply a thin line around the edges and a thicker bead in recessed areas.

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Work quickly — the foam expands and hardens fast.

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• Install the new plywood sheet with proper alignment, leaving slight gaps between sheets to allow for expansion/contraction due to humidity. Screw from the center outward, spacing screws 6 inches apart.

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• If the gap between plywood sheets is too large, fill it with foam, let it dry, cut it flush, and apply drywall tape. This prevents sagging and ensures a smooth, durable surface. </aside>