OSB vs Plywood for Roof Sheathing: Which Is Better?

Quick answer

Both OSB and plywood are approved for roof sheathing when they carry the same span rating. OSB is usually cheaper and more uniform, which is why most new homes use it. Plywood handles leaks and repeated wetting better and dries out faster. For a re-roof in a wet climate or under heavy materials, many roofers prefer plywood.

Cheaper

OSB

Moisture

Plywood

Code

Both OK

OSB (oriented strand board) and plywood both work as roof decking. The choice comes down to budget, climate and how much risk of water you expect. Here is a straight comparison and the actual cost difference on a real roof.

OSB vs plywood at a glance

Factor	OSB	Plywood
Cost	Usually lower	Usually higher
Code acceptance	Yes, by span rating	Yes, by span rating
Consistency	Very uniform, no voids	Can have voids and knots
Moisture	Absorbs slowly, dries slowly, edges can swell	Absorbs faster, dries faster, less permanent swelling
Weight (same thickness)	Slightly heavier	Slightly lighter
Nail holding	Similar for roof use	Similar for roof use
Stiffness	Similar at the same span rating	Similar at the same span rating
Common use	Most new homes	Re-roofs, wet climates, premium builds

The moisture difference, explained

Both products should stay dry. The difference shows up when something goes wrong, like a small leak or wet weather during the job.

OSB takes on water slowly but also releases it slowly. Edges that soak up water can swell and telegraph through shingles as ridges.
Plywood gets wet faster but dries faster and usually returns closer to its original shape.

Good attic ventilation, quick dry-in with underlayment and a 1/8 inch gap between panels prevent most problems with either.

Cost example: a 2,000 sq ft roof

Sheets needed: 2,000 ÷ 32 = 62.5
Add 10% for cuts: 69 sheets
Price difference: if OSB is $X less per sheet than plywood where you buy, you save 69 × X.

If plywood costs this much more per sheet	Extra cost for the roof
$3	$207
$5	$345
$8	$552
$10	$690

Prices move a lot with lumber markets, so check your local yard. On most re-roofs, decking is a small part of the total cost, and replacement is usually priced per sheet.

Get your exact roof area from the roof square footage calculator and divide by 32 for sheets.

Which one should you choose?

Choose OSB if:

You want the lowest cost with code-compliant performance
The roof will be dried-in quickly and the attic is well ventilated

Choose plywood if:

You live in a wet or humid climate, or the job may sit open in rain
You are replacing a few damaged sheets on an older plywood deck
You are installing heavy materials and want a stiffer, more forgiving deck

Whichever you pick, match the thickness and span rating to your rafter spacing. See roof sheathing thickness and what size plywood for a roof, then fasten it right with roof sheathing nails and spacing.

Frequently asked questions

Is OSB or plywood better for a roof?

Neither is better in every case. OSB costs less and is very consistent. Plywood tolerates moisture better and dries faster. If the roof is well ventilated and installed quickly, both perform well.

Why do builders use OSB instead of plywood?

OSB is usually less expensive, comes in consistent quality with no voids and is made from smaller, fast-growing trees. It meets the same code requirements when the span rating matches.

Does OSB swell when wet?

OSB edges can swell when they absorb water and may not fully shrink back. Modern OSB has edge sealing, and products with water-resistant overlays are available. Keep it dry and covered during installation.

Can you mix OSB and plywood on a roof?

Yes, as long as the panels are the same thickness and meet the required span rating. Roofers often replace damaged sheets with whatever matches the existing thickness.

Figures are typical US values for planning. Building codes, product specs and local prices vary, so confirm with your local code office, the product's installation guide and a licensed roofer. See how we write and check our guides.