Introduction
OSB, plywood, or ZIP? 7/16-in or 15/32-in? The panel you choose affects your budget, your installation steps, and how the assembly performs for decades — but it barely changes your sheet count, because every structural panel comes in the same 4×8 ft (32 ft² / 2.98 m²) unit. Choose the material on performance and price, then run the Sheathing Calculator to get the quantity. This guide covers the panel families, thicknesses, and ratings you need to choose well.
The Three Panel Families
OSB (oriented strand board)
Wood strands pressed with resin into a uniform mat. OSB is the workhorse of modern residential sheathing: typically less than half the price of comparable plywood, dimensionally consistent from sheet to sheet, and available in every standard thickness. Its weakness is moisture — exposed edges swell if soaked repeatedly, so prompt covering with underlayment or wrap matters. Standard wall/roof grade is 7/16-in (11.1 mm).
Plywood (CDX / structural)
Cross-laminated veneer layers. Structural plywood costs roughly double OSB per sheet but tolerates wetting and drying cycles more gracefully, holds nails slightly more tenaciously, and is the traditional choice where a panel may see weather before the building is dried in. Common sheathing grades are 15/32-in (11.9 mm) and 1/2-in (12.7 mm).
ZIP System (and similar coated panels)
An OSB core with a factory-applied water-resistive barrier and taped seams — sheathing and housewrap in one step. Per-sheet cost runs well above plain OSB ($35–$55 typical), but it eliminates the separate housewrap material and labor, so installed cost is often comparable on hired jobs. The taped seams double as the air barrier. Requires the manufacturer’s tape and installation details to perform as designed.
| Factor | OSB | Plywood | ZIP / coated |
|---|---|---|---|
| Typical 4×8 price | $10–$18 | $28–$48 | $35–$55 |
| Moisture tolerance | Fair — protect edges | Good | Good (sealed face) |
| Fastener holding | Good | Very good | Good |
| Install steps | Sheathe, then wrap | Sheathe, then wrap | Sheathe, tape seams |
| Best for | Budget-driven builds | Wet climates, re-roofs | Speed, air-sealing |
Prices are typical US retail planning ranges and move with the lumber market — the cost guide has the full budget picture.
Thickness and Span Ratings
Structural panels carry an APA-style span rating stamped on the sheet, written as two numbers: roof span / floor span in inches on center. A 24/16 panel may span 24-in roof framing or 16-in floor framing. Match the rating to your actual framing spacing — this is the specification that matters, more than the nominal thickness.
| Common thickness | Typical span rating | Common uses |
|---|---|---|
| 7/16 in (11.1 mm) OSB | 24/16 | Walls, roofs at 16–24 in o.c. |
| 15/32 in (11.9 mm) plywood | 32/16 | Walls, roofs at 16–24 in o.c. |
| 1/2 in (12.7 mm) | 32/16 | Walls, roofs |
| 5/8 in (15.9 mm) | 40/20 | Roofs at 24 in o.c., some floors |
| 3/4 in (19.1 mm) T&G | 48/24 | Subfloors |
Note the first row: 7/16-in OSB rated 24/16 is fine on 16-in studs but at 24-in rafter spacing the panel edges between supports need H-clips or other edge support. Buying a thicker panel than your spacing requires is money spent for stiffness you may not need; buying thinner than required is a code and performance failure. When in doubt, confirm with your local building authority.
Specialty Panels
Tongue-and-groove subfloor
Subfloor panels (usually 23/32-in OSB or 3/4-in plywood) have interlocking T&G edges that align the joints and share loads between joists — no H-clips needed. Standard practice is construction adhesive on the joists plus ring-shank nails or screws at 6 in on edges, 12 in in the field. The glue is what kills squeaks, not just the fasteners.
Radiant barrier sheathing
Roof panels with a foil face that reflects radiant heat, reducing attic temperatures in hot climates. Installed foil-side down into the attic airspace (it needs the air gap to work). Costs more per sheet than plain OSB; the payback is in cooling climates.
Fire-retardant-treated (FRT) plywood
Plywood pressure-treated for reduced flame spread, used where code requires it — typically near property lines, in certain multifamily construction, or in wildfire-prone areas. It’s a code-driven choice, not a performance upgrade; confirm requirements with your local authority before assuming you need (or don’t need) it.
Treated panels for exposed or ground-contact use
Standard sheathing is not rated for ground contact or permanent weather exposure. Where panels will see those conditions (shed skirting, exposed soffits), use preservative-treated panels rated for the exposure — and check that the treatment is compatible with your fasteners, since some treatments corrode standard steel.
Matching Panel to Project
- Shed / garage walls: 7/16-in OSB is the economical default; plywood if the panels will sit uncovered through a wet season.
- House walls: 7/16-in OSB or 15/32-in plywood at 16-in studs; ZIP if you want the wrap step eliminated and are paying for labor.
- Roof deck: 7/16-in OSB at 16-in rafters; 15/32-in or 5/8-in at 24-in spacing (with H-clips where required); radiant barrier in hot climates.
- Subfloor: 3/4-in (23/32-in) T&G, glued and fastened — this is the one place not to economize on thickness.
- Tall walls (9–10 ft): consider 4×9 or 4×10 sheets to avoid a horizontal mid-wall seam; they cost more per sheet but compare per square foot.
Once you’ve chosen the panel, the quantity math is identical for all of them — run it in the Sheathing Calculator. For installation technique once the panels arrive, see the pro tips guide; for the measuring methods that produce the area you enter, see the estimating guide.
Related Guides
- Sheathing Calculator: The Complete Guide — terminology, formulas, and a worked example.
- Sheathing Calculator: Cost Guide — per-sheet prices and project budgets.
- Sheathing Calculator: Estimating Guide — measuring each surface type.
- Sheathing Calculator: Pro Tips — storage, layout, and fastening.
- Sheathing Calculator: Code Compliance — what the building code typically requires.
- Sheathing Calculator FAQ — quick answers to the most asked questions.
Frequently Asked Questions
Is OSB as strong as plywood for sheathing?
At equal thickness and span rating, yes — both are rated by the same span-rating system and both are accepted as structural sheathing. The practical differences are moisture tolerance and fastener holding, not rated strength.
What does 24/16 mean on a sheet of OSB?
It’s the span rating: the panel may span up to 24 in on center as roof sheathing or 16 in on center as floor sheathing. Always match the rating to your actual framing spacing.
Is ZIP sheathing worth the extra cost?
It depends on your labor situation. The panels cost more per sheet but eliminate housewrap material and installation labor, and the taped seams provide the air barrier. On DIY jobs where your labor is “free,” plain OSB plus housewrap is usually cheaper; on hired jobs the installed cost is often close.
Can I use 7/16-in OSB on 24-in rafters?
A 24/16-rated 7/16-in panel is rated for 24-in roof spans, but the unsupported edges between rafters typically need H-clips, tongue-and-groove edges, or blocking. Confirm the exact requirement with your local building authority.
What’s the difference between CDX and OSB sheathing?
CDX is a plywood grade (C-face, D-back, exterior glue); OSB is a different product made from pressed strands. Both serve as structural sheathing at comparable thicknesses. CDX typically costs roughly double equivalent OSB.
Get Your Number
Pick your panel from the guidance above, then get the quantity from the Sheathing Calculator — 32 ft² (2.98 m²) per sheet regardless of which family you choose, plus your waste allowance, rounded up.
Disclaimer: Calculator results are planning estimates. Panel availability, grades, and code requirements vary by region — verify the span rating against your framing spacing, confirm requirements with your local building authority, and check current pricing with your supplier.
