Roof Underlayment vs Plywood

Roofs are more than shingles. Beneath them, plywood decking provides structure, while underlayment adds waterproofing. Here’s how they differ and why both are essential.

• Plywood: Structural layer; supports shingles, tiles, or metal roofing.
• Underlayment: Protective layer (felt or synthetic) that prevents water penetration.

Learn how to calculate plywood with our Plywood Calculator Guide.