What Kind of Wood Deck for Roofing? A 2025 Guide for Homeowners

Building or repairing a roof starts from the bottom—specifically, the roof deck, also known as roof sheathing. The wood decking provides the structural base that supports underlayment, shingles, and other roofing materials. But not just any wood will do. Understanding what kind of wood deck to use is essential for a strong, durable, and code-compliant roof.

This comprehensive guide explores:

What is wood decking & why it matters
Most common decking lumber types
Performance & cost of each wood option
OSB vs. plywood comparison
Thickness & code requirements
Pressure-treated decking considerations
Engineered wood options
Decking installation best practices
Moisture management & ventilation
Repair and replacement tips
Environmental & sustainability factors
Cost breakdowns & budgeting tips
Frequently asked questions
Final verdict

1. What Is Roof Decking (Sheathing) & Why It Matters

The roof deck is the layer of wood (or plywood/OSB) fastened atop roof trusses or rafters. It functions as:

A stable base for shingles, metal roofing, or tiles
A structural diaphragm that ties rafters together
A barrier that bears weight and resists wind uplift
A substrate for underlayment and ventilation systems

Using the wrong material or poor-quality decking compromises the entire roofing system, leading to sagging, leaks, and faster deterioration.

2. Common Types of Wood Used for Roof Decking

a. Plywood

Constructed by gluing multiple wood veneers in cross-grain layers
Grades include A‑C, CDX (exposed side), with CDX × 4/4 being typical for roofs
Available in 4×8 sheets
Offers high strength, stiffness, and screw/nail holding resistance

b. Oriented Strand Board (OSB)

Comprised of wood strands glued in layered, cross-directional patterns
Typically rated for roof/roofing installation
Comes in 4×8 sheets, comes in 7/16″, 5/8″, or 3/4″
Cost-effective alternative to plywood

c. Solid Wood Plank (Tongue & Groove)

Used on rafters in older homes or specialized architectural styles
Tongue-and-groove boards interlock tightly
Offers traditional look and can be left exposed underneath

d. Engineered Wood Panels

Glued-wafer boards, fiberboards, or OSB derivatives
Rarely used alone on residential roofs unless approved by manufacturer

3. Performance & Cost Comparison

Material	Strength	Cost	Availability	Best For
CDX Plywood 5/8″	High	Moderate–High	High	Standard residential & code compliance
CDX Plywood 3/4″	Very High	Higher	Moderate	Heavy snow/wind zones or tile/metal roofs
OSB 7/16″	Moderate	Lowest	High	Budget-conscious builds (mild climates)
OSB 5/8″ / 23/32″	Moderate–High	Mid	High	Standard load roofs, moderate climates
Tongue & Groove Wood	High	Highest	Low	Historical, decorative, or open underside
Engineered Panels	Varies	Varies	Limited	Designed systems with warranty approval

4. Plywood vs. OSB: Head-to-Head

Strength & Durability

Plywood: Stronger, more impact-resistant, better nail/screw holding
OSB: Slightly less strong; prone to swelling at edges if wet

Moisture Tolerance

Plywood: Handles moisture better with less swelling
OSB: Soaks up water at edges and swells more

Cost & Environmental

OSB: ~10–20% cheaper per sheet
Environmental: OSB uses smaller wood, plywood uses higher-grade veneers

5. Decking Thickness & Building Code Guidelines

Minimum thickness depends on rafter spacing and material:

7/16″ OSB or plywood: Permitted for rafter spacing of 24″ OC in mild conditions
5/8″ plywood or 23/32″ OSB: Standard for 16″ OC; better for moderate climates
3/4″ plywood or OSB: Used in high-wind/snow regions or for heavier roof coverings

Check local building code and product specs for precise requirements.

6. Should You Use Pressure-Treated Decking?

Pressure-treated decking resists rot and insects but may:

Be more expensive
Require special fasteners (stainless steel or hot-dipped galvanized) due to corrosion
Not be necessary in dry, temperate climates unless subject to ground-level exposure

It’s usually only needed in extreme damp/wet environments.

7. Engineered Wood Decking Options

Engineered panels—like Oriented Strand Lumber (OSL) or structural fiberboard—are offered by some manufacturers. Benefits include high dimensional stability and moisture resistance.

However, using them requires:

Compliance with roofing system specs
Manufacturer warranties supporting panels, underlayment, and shingles in one integrated system

8. Best Practices for Decking Installation

Layout & Sheathing Direction

Run panels perpendicular to rafters or trusses
Stagger joints for structural integrity

Fastening

Nail or screw per manufacturer’s pattern
- Example: 6″ OC at edges, 12″ in field
Countersink fasteners flush

Gapping

Leave a 1/8″ space between panels to allow expansion
On OSB edges, use a file or scribing tool to lightly taper the edge if needed

Blocking & Support

Use solid blocking/support at edges and hips for strength
Provide support at rafter beam intersections

Ventilation

Install ridge and soffit vents
Maintain clear airflow pathways to stabilize interior moisture

9. Moisture Management & Ventilation Matters

Wood decking must remain dry:

Ventilation under the deck: Crucial for attic moisture control
Proper underlayment: Ice/water shield in eaves prevents leaks
Flashing and drip edge: Guide water off the deck
Prompt repair of leaks: Prevents rot from forming under shingles

10. Repairs & Replacements

Spot Repair Decking

Minor damage (e.g., rot, puncture under flashing) can be repaired by cutting out affected section and fitting a patch with proper fasteners and underlayment shares.

Complete Reroof

If the deck has multiple soft spots or extensive age-related wear, replace:

Remove deck to rafters
Install new plywood or OSB per thickness
Apply underlayment and roofing materials

11. Sustainability & Wood Choice

Environmental Considerations

OSB: Efficient use of fast-growing wood and minimal waste
Plywood: Requires higher-grade veneer, sourced from larger logs
Solid planks: Often milled from old-growth timber; less sustainable

Certifications

Look for products with FSC (Forest Stewardship Council) or SFI (Sustainable Forestry Initiative) for responsible sourcing.

12. Cost Estimates & Budgeting Tips

Typical decking costs (materials only):

7/16″ OSB: $12–$18/sheet → ~$0.40–$0.55/sq ft
5/8″ CDX plywood: $25–$35/sheet → ~$0.80–$1.10/sq ft
3/4″ plywood: $35–$50/sheet → ~$1.10–$1.65/sq ft

Allow for waste (5–10% extra) and fasteners:

Nails/screws bundle: ~$1–$3 per sheet install

13. FAQ: Choosing the Right Deck for a Roof

Q1: Can you use OSB under metal or tile roofs?
A: Yes; use thicker (5/8″ or 3/4″) OSB and ensure proper underlayment. Even then, plywood may still hold nails better.

Q2: Does decking type affect roof ventilation?
A: No—the decking isn’t ventilated directly. But a correctly ventilated roof assembly does make decking last longer.

Q3: Can I overlay decking over old plywood?
A: Mixing new and old contributes to uneven roof surface. Remove old decking for a flush substrate.

Q4: Are engineered panels worth it?
A: They offer some advantages, but cost and code acceptance limit use to specialty systems.

14. Final Verdict: Best Decking Type by Situation

Budget-conscious new build: 7/16″ OSB (with proper ventilation and underlayment)
Higher performance and longevity: 5/8″ or 3/4″ CDX plywood
High-wind or heavy roof load (tile, stone-coated metal): 3/4″ plywood
Traditional or exposed underside: Tongue & groove wood if aesthetics matter
Green certifications needed: FSC/SFI plywood or certified OSB
Pressure-treated: Only in moisture-prone or code-required areas

15. Key Takeaways

The roof deck is your roof’s foundation—choose wisely
Plywood is generally stronger and more durable than OSB
OSB saves cost and works well in proper installation
Thickness depends on span, climate, and roofing material
Fastening, cross-nailing, and boarding standards are critical
Ventilation and moisture control prolong decking life
Replacing decking may be necessary when performance suffers
Sustainability credentials influence wood choice

16. Conclusion

Selecting what kind of wood deck for roofing impacts everything—from structural support to roof lifespan. Whether you choose economical OSB or resilient plywood, your decisions should be guided by building code, climate, material costs, roof type, and long-term durability goals.

Proper installation—with attention to decking thickness, fastening pattern, expansion gaps, venting, and quality control—ensures your roof stands the test of time. Armed with this guide, you’re ready to choose with confidence and understand why your roofer might recommend one decking style over another.

Let your new or repaired roof stand strong—beginning from the deck up.

If you’d like help creating a cost estimator, local keyword optimizations, or roofing landing page content, I’m happy to assist further!

What Kind of Wood Decking for Roofing?