🪵 OSB vs Plywood for Roof Sheathing — Which is Better?
When building or re-roofing, the choice between OSB (Oriented Strand Board) and plywood can have a big impact on roof durability, cost, and performance. Both materials are engineered wood panels used as the roof deck beneath underlayment and shingles. This guide breaks down the differences in strength, moisture resistance, price, and installation to help you decide which is best for your project.
📊 Quick Comparison: OSB vs Plywood
| Feature | OSB | Plywood |
|---|---|---|
| Cost | 💲 More affordable | 💲💲 Slightly higher cost |
| Strength | Strong, uniform panels | Slightly stronger under load |
| Moisture Resistance | Can swell if saturated | Dries faster, less swelling |
| Weight | Heavier | Lighter and easier to lift |
| Availability | Widely available, standard size | Slightly less uniform |
| Best Use | Large roofs, budget builds | Premium or humid climates |
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🧰 Installation Tips for Roof Decking
- Use panels with the “Exposure 1” or “Exterior” rating for roof sheathing.
- Leave a 1/8-inch gap between sheets to allow expansion.
- Install panels perpendicular to rafters for maximum strength.
- Use 8d ring-shank nails spaced 6" on edges and 12" in the field.
- Ensure roof decking is completely dry before adding underlayment or shingles.
✅ Pros of OSB
- Lower cost per sheet
- Uniform density and smooth surface
- Widely available in 4×8 sheets
- Strong nail-holding capacity
✅ Pros of Plywood
- Better performance in high humidity
- Dries faster after exposure
- Less prone to edge swelling
- Lighter and easier to install overhead
✅ Best Practice:
In dry or temperate climates, OSB is an excellent and cost-effective choice.
In humid, coastal, or cold regions where moisture is a concern, plywood is worth the extra cost for long-term reliability.
❓ FAQ – OSB vs Plywood for Roofs
Q: Which lasts longer, OSB or plywood?
Plywood typically lasts longer in moist conditions due to its layered veneer construction and faster drying time.
Q: Can OSB be used under shingles?
Yes, as long as it’s rated Exposure 1 or Exterior and kept dry before underlayment installation.
Q: Does OSB warp more than plywood?
OSB tends to swell along edges when exposed to water, while plywood resists warping better.
Q: What thickness should roof decking be?
Minimum 7/16″ for OSB and 3/8″ for plywood, but 1/2″ is recommended for better rigidity.
Q: Can you mix OSB and plywood on the same roof?
It’s possible, but not ideal — differences in expansion and texture can cause uneven shingle surfaces.
⚠️ Safety Reminder
Always wear gloves and safety glasses when cutting or handling roof sheathing panels. Use proper fall protection when working at heights, and never walk on unsupported decking.
📚 Related Guides:
Plywood Estimator •
Roof Area Calculator •
Roof Tear-Off Cost Estimator