OSB (oriented strand board) costs 15–30% less than plywood and works fine for most sheathing and subflooring. Plywood handles moisture better and is stronger in specific applications. Here's when each one is the better choice.
Short answer: Use OSB for wall sheathing and roof decking when budget matters. Use plywood for subfloors, anywhere exposed to moisture, and when you need a smoother surface. Both are code-approved for structural sheathing.
| Factor | OSB | Plywood |
|---|---|---|
| Cost (4×8 sheet, ½") | $25–$35 | $35–$55 |
| Cost (4×8 sheet, ¾") | $35–$50 | $50–$75 |
| Strength (shear) | Slightly stronger | Slightly weaker |
| Strength (bending) | Slightly weaker | Slightly stronger |
| Moisture resistance | Absorbs moisture, swells at edges | Handles moisture better, dries faster |
| Weight (½" sheet) | ~46 lbs | ~40 lbs |
| Surface | Rough, uneven | Smooth (especially sanded grades) |
| Span rating | Equal (matched by grade) | Equal (matched by grade) |
| Code approved | Yes — structural sheathing | Yes — structural sheathing |
| Nail holding | Good | Good |
| Availability | Very common | Common but fewer grades in stock |
| Application | Recommended |
|---|---|
| Wall sheathing | OSB |
| Roof decking | Either |
| Subfloor | Plywood (preferred) |
| Shed floor | Plywood |
| Shed walls/roof | OSB |
| Cabinet backing | Plywood |
| Shelving | Plywood |
| Concrete forms | Plywood (or form-grade) |
| Exterior (exposed) | Neither — use treated plywood |
| Application | Minimum | Common Choice |
|---|---|---|
| Wall sheathing | 7/16" | 7/16" OSB or ½" plywood |
| Roof decking (16" OC rafters) | 7/16" | 7/16" or ½" |
| Roof decking (24" OC rafters) | ⅝" | ⅝" or ¾" |
| Subfloor (16" OC joists) | ⅝" | ¾" T&G plywood |
| Subfloor (24" OC joists) | ¾" | ¾" T&G plywood |
| Shed floor | ¾" | ¾" plywood |
This is the biggest practical difference. Both materials are affected by moisture, but they respond differently. OSB absorbs water more slowly than plywood but once it does absorb water, it swells (especially at the edges) and takes much longer to dry out. Plywood absorbs water faster but also releases it faster, and it doesn't swell permanently at the edges.
What this means in practice: if your subfloor gets rained on during construction, plywood will dry out and flatten. OSB may stay swollen at the seams permanently, creating ridges under your finished floor. For roof decking, a small leak can cause OSB to swell and delaminate, while plywood handles occasional moisture better.
For a typical project, OSB saves real money:
| Project | OSB Cost | Plywood Cost | Savings |
|---|---|---|---|
| 10×12 shed (floor + walls + roof) | $600–$875 | $875–$1,375 | $275–$500 |
| Roof re-decking (1,500 sq ft) | $1,645–$2,350 | $2,350–$3,525 | $700–$1,175 |
| Subfloor (1,200 sq ft) | $1,330–$1,900 | $1,900–$2,850 | $570–$950 |
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For structural sheathing, they're essentially equal — both carry the same span ratings and code approvals. OSB is slightly stronger in shear (racking resistance), while plywood is slightly stronger in bending. For most residential construction, the difference doesn't matter.
You can, and many builders do. However, plywood is generally preferred for subfloors because it handles moisture better (spills, leaks, construction delays) and tongue-and-groove plywood panels lay flatter, resulting in fewer squeaks and ridges under finished flooring.
No. Neither OSB nor standard plywood is waterproof. OSB is more vulnerable to moisture damage, especially edge swell. For truly wet environments, use pressure-treated plywood or marine-grade plywood.
Manufacturing efficiency. OSB uses smaller, fast-growing trees and waste wood strands, pressed with resin into large sheets. Plywood requires larger logs peeled into thin veneers and layered, which is more material-intensive and labor-intensive.
Yes. Many builders use OSB for wall sheathing and roof decking (where cost savings add up) and plywood for subfloors and areas where moisture is a concern. This is a practical, cost-effective approach.
If you're using it as attic storage flooring over joists, plywood is better — stiffer underfoot and handles the occasional roof leak without swelling. For pure ceiling sheathing that won't bear weight, OSB is fine.