The plywood used for roofing is typically exterior-grade plywood, which is stronger and more water-resistant than interior plywood. This type of plywood serves as the base layer under your shingles or other roof materials. It keeps your roof sturdy and helps prevent leaks. Most roofers use plywood that is either 1/2 inch or 5/8 inch thick. The thicker plywood is better for durability and can last longer before needing repair.
What Grade of Plywood Works Best?
Exterior-grade plywood is the best choice for roofing because it has a waterproof glue that holds the layers together. This glue keeps moisture out, which is critical for roof longevity. Interior plywood uses a weaker glue that can fail when exposed to rain and snow.
You will also see “CDX” plywood marketed for roofing. The “C” and “D” refer to the quality of the wood surfaces. The “X” means it has exterior-grade glue. CDX plywood costs less than premium grades but still offers good protection. Many roofers use CDX as a standard choice for residential roofing projects.
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How Thick Should Roof Plywood Be?
Most residential roofs use either 1/2 inch or 5/8 inch thick plywood. The 1/2 inch thickness works for standard roof frames with rafters spaced 16 inches apart. For rafters spaced 24 inches apart, 5/8 inch plywood is required for proper support.
Thicker plywood provides better insulation and longer lifespan. According to industry data, roof installation costs range from $4 to $40 per square foot, and using premium plywood thickness can help protect that investment. A 1,700 sq. ft. roof project could cost between $6,800 and $68,000 depending on materials chosen.
Plywood Vs. Other Roof Decking Materials
Plywood is the most common roof decking material in the United States. Other options include OSB (oriented strand board) and metal decking, but plywood remains the standard choice. Here is how they compare:
| Material | Cost | Durability | Water Resistance |
|---|---|---|---|
| Exterior Plywood | Medium | High | Excellent |
| CDX Plywood | Lower | Good | Good |
| OSB Decking | Lower | Medium | Fair |
| Metal Decking | Higher | Very High | Excellent |
Why Plywood Quality Matters for Your Roof
Poor quality plywood can sag or rot over time, especially in wet climates. According to RubyHome (2025), the average roof replacement cost is $9,526, and using quality plywood decking helps avoid costly repairs later. If your plywood fails, water can leak into your attic and damage insulation and framing.
Quality plywood also helps your shingles last longer. According to industry data, asphalt shingles typically last 20 to 30 years, but a solid plywood base is essential for reaching that lifespan. Proper ventilation and a strong decking layer work together to protect your entire roof system.
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Contact a qualified roofing company for expert guidance on roof repair, replacement, or installation.