Best Plywood to Use for Roof Sheathing

Choosing the right plywood for roof sheathing affects structural performance, weather resistance, and long-term durability of a roof. This article explains plywood types, thicknesses, span ratings, exposure classes, installation tips, and alternatives to help homeowners and contractors select the best plywood for roof projects across the United States.

Plywood Type	Typical Thickness	Span Rating / Use	Key Pros	Key Cons
CDX Plywood	1/2″, 5/8″, 3/4″	Rafter/Truss Spacing Up To 24″ O.C.	Economical, widely available	Lower face quality, needs protection from moisture
Exterior-Grade Hardwood Plywood	5/8″, 3/4″	Higher Strength Applications	Durable, better veneer	More expensive
Advantech / Structural OSB	7/16″, 1/2″, 3/4″	Comparable To Plywood For Sheathing	Good stiffness, engineered for load	Swells If Exposed Prolonged Time
Marine Plywood	1/2″, 5/8″, 3/4″	Extreme Moisture Areas	Superior water resistance	High cost, usually unnecessary for standard roofs

What Plywood Types Are Recommended For Roof Sheathing

For most residential roofs, CDX exterior-grade plywood is the industry standard, offering a balance of cost and performance. CDX is made with exterior adhesive and is labeled for construction use, making it suitable for roof sheathing when covered promptly with underlayment and shingles.

Higher-grade exterior hardwood plywood or structural-rated plywood may be chosen for longer spans, heavy snow loads, or where a smoother nailing surface is desired. Marine plywood is over-specified for typical roofs and reserved for exposed, wet environments.

Thickness And Span Ratings: How Thick Should Roof Plywood Be

Plywood thickness impacts stiffness, deflection, and the spacing of rafters or trusses. Common roof sheathing thicknesses include 7/16″ (11/32″), 1/2″, 5/8″, and 3/4″. Selection depends on rafter/truss spacing and loading conditions.

Typical guidelines: for 24 inches on-center rafters, 5/8″ or 3/4″ plywood is recommended to reduce deflection. For 16 inches on-center, 1/2″ plywood is usually sufficient. Building codes and span tables should be consulted for exact requirements based on species, grade, and load.

Exposure Durability And Plywood Grades

Exterior plywood uses different exposure classifications that indicate glue bond durability when exposed to moisture during construction. Exterior or Exposure 1 grades use waterproof adhesives suitable for roof sheathing. Avoid interior-bond plywood for roofs.

Plywood faces are graded with letters (A, B, C, D). For sheathing, CDX combines a C face and D back with “X” exposure-rated adhesive; the face quality is less important than structural integrity, but better faces improve handling and underlayment contact.

Engineered Sheathing Options: OSB Vs Plywood

Oriented Strand Board (OSB) is a common alternative to plywood. Modern structural OSB panels like Advantech or other engineered brands offer consistent thickness and stiffness and are often less expensive than plywood.

OSB and plywood both meet code for roof sheathing when properly specified. OSB can be more sensitive to prolonged wet exposure and may swell if left exposed during long construction delays; plywood tends to hold up better against intermittent moisture exposure.

Fasteners, Nailing Patterns, And Attachment Guidelines

Proper fastening is critical. Typical practice uses 8d or 10d common galvanized nails or ring-shank nails. Fastener spacing commonly recommended is 6″ on center at panel edges and 12″ on center in the field, but follow local code or manufacturer instructions.

Stagger panel joints and leave a 1/8″ gap between panels to allow for expansion, unless using tongue-and-groove or OSB panels specified otherwise. Use approved adhesive for additional shear capacity in high-wind or seismic zones if required by code.

Underlayment, Ventilation, And Roof Application Considerations

Plywood sheathing must be covered promptly with roofing underlayment (synthetic or felt) and shingles to prevent prolonged exposure. Underlayment protects sheathing from moisture and provides a secondary barrier.

Proper attic ventilation reduces long-term moisture and heat exposure to the plywood. Continuous ridge and soffit ventilation or equivalent systems help maintain sheathing longevity and reduce ice dam risk in cold climates.

Climate And Moisture: Choosing Plywood For Different Regions

In humid coastal areas or regions with frequent rain, choose plywood with a reliable exterior glue line and consider treated or higher-grade panels. In cold climates with heavy snow, prioritize thicker panels for increased stiffness and load capacity.

For areas prone to hurricanes or high winds, follow local structural requirements, which may call for higher-grade structural plywood or specific nailing schedules to resist uplift forces.

Cost, Availability, And Practical Buying Tips

CDX is typically the most cost-effective and widely available sheathing material. Engineered or hardwood exterior plywood costs more but offers improved surface and sometimes higher strength. OSB often provides the lowest cost per panel with acceptable performance for many projects.

Buy panels from reputable suppliers and inspect for defects like delamination, significant voids, or water damage. Check manufacturer grade stamps and exposure ratings on each panel before purchase to confirm suitability for roof sheathing.

Common Mistakes To Avoid When Choosing Roof Plywood

Common errors include using interior-grade plywood, undersizing plywood thickness for span and load, and leaving sheathing exposed to weather during construction. Always confirm span ratings and exposure classifications before installation.

Another mistake is inadequate fastening: improper nail type, spacing, or failure to follow manufacturer or code requirements can compromise roof performance and void some warranties.

Maintenance And Inspection For Roof Sheathing

After installation, periodic attic inspections can detect signs of sheathing problems such as sagging, water stains, or rot. Address roof leaks promptly to prevent plywood deterioration.

If shingle replacement is deferred or there has been a known leak, inspect sheathing from the attic and, if necessary, remove shingles to check for delamination or soft spots. Replace damaged panels with the same thickness and grade specified by local code.

Buying Checklist: How To Select The Right Roof Plywood

• Confirm Plywood Type: Exterior-grade CDX, structural exterior plywood, or engineered OSB.
• Choose Thickness: Match panel thickness to rafter/truss spacing and load using span tables.
• Verify Exposure Rating: Ensure “Exterior” or “Exposure 1” glue lines.
• Inspect Panels: Look for delamination, voids, or water stains.
• Consider Climate: Choose higher-grade panels for coastal or persistently wet regions.
• Follow Local Code: Confirm nailing schedules and any engineered sheathing requirements.

Frequently Asked Questions About Roof Plywood

Is 1/2 Inch Plywood Acceptable For A Roof?

1/2″ plywood is acceptable when rafters or trusses are spaced at 16″ on center and local code or span tables allow it. For 24″ on-center spacing, thicker panels are recommended to control deflection and meet code.

Can CDX Plywood Be Used For Roof Sheathing?

Yes. CDX is the common, economical choice for roof sheathing provided it has the correct exposure rating and is covered with underlayment and shingles without prolonged exposure to weather.

Is Plywood Better Than OSB For Roofing?

Both perform well when properly specified. Plywood may resist moisture-related edge swelling better, while OSB offers consistent panel strength and cost savings. Choice depends on climate, project timeline, and local availability.

When Is Marine Plywood Necessary?

Marine plywood is rarely necessary for standard residential roofs. It is designed for constant water exposure and is used in marine or extremely wet, exposed construction; for most roofs, exterior-grade plywood or engineered sheathing is sufficient.

Resources And Reference Guidance

Relevant resources include local building codes, APA – The Engineered Wood Association span tables, and manufacturer installation guides. Consult local code officials or a structural engineer for designs in high-wind, seismic, or heavy-snow regions.

Following these guidelines helps ensure that the chosen plywood provides a durable and code-compliant base for roofing materials while minimizing future maintenance and repair needs.