Wall sheathing under the 2021 International Residential Code (IRC) must be fastened directly to the studs and must meet Table R602.3(3) where it resists wind pressure. That table lists 3/8 inch (24/0) panels on studs at 16 inches on center and 7/16 inch (24/16) panels on studs at 16 or 24 inches on center.
Wall sheathing is the structural panel or board layer fixed to the outside face of the studs, under the siding and water-resistive barrier. In wood-frame houses it is usually oriented strand board (OSB) or plywood, and it stiffens the wall and resists wind pressure.
Key facts
- Wall sheathing on the exterior side of an exterior wall must be fastened directly to framing members and conform to Table R602.3(3) (2021 IRC Section R602.3).
- Wood structural panel wall sheathing must conform to DOC PS 1, DOC PS 2, ANSI/APA PRP 210, CSA O325 or CSA O437 and carry a grade mark or certificate of inspection (2021 IRC Section R604.1).
- A 3/8 inch panel with a 24/0 span rating is listed only for studs spaced 16 inches on center, with a 6d common nail at 6 inches on center at edges and 12 inches in the field (2021 IRC Table R602.3(3)).
- A 7/16 inch panel with a 24/16 span rating is listed for studs at 16 or 24 inches on center, with an 8d common nail at the same 6 and 12 inch spacing (2021 IRC Table R602.3(3)).
- Wall sheathing used only as a base for the exterior wall covering must comply with Section R703 instead (2021 IRC Section R602.3).
- Braced wall panels have separate rules in Section R602.10 (2021 IRC Table R602.3(3), footnote b).
What does the IRC say about wall sheathing?
The IRC sets three basic rules in Section R602.3: sheathing goes directly onto the framing, sheathing on the outside of an exterior wall must resist the wind pressures in Table R301.2.1(1) (adjusted for height and exposure using Table R301.2.1(2)), and it must conform to Table R602.3(3). Sheathing that exists only to carry the exterior wall covering follows Section R703.
Wood structural panels get their own short section, R604. It says the panels must meet one of the listed product standards, must be identified by a grade mark or certificate of inspection from an approved agency (R604.1), must not exceed the spans in Table R602.3(3) (R604.2), and must be attached in accordance with Table R602.3(1) or R602.3(3) (R604.3).
The adopted code edition and local amendments govern. This is a prescriptive reading of the 2021 text, not an engineering check, and structural insulated panels and proprietary sheathing follow the manufacturer's tables and instructions.
How thick does wall sheathing need to be?
Table R602.3(3) allows a 3/8 inch panel (span rating 24/0) with 16 inch stud spacing, and a 7/16 inch panel (span rating 24/16) with 16 or 24 inch stud spacing.
2021 IRC Table R602.3(3), requirements for wood structural panel wall sheathing used to resist wind pressures. Panel strength axis parallel or perpendicular to supports (see footnote a).
| Minimum nominal panel thickness (inch) | Span rating | Maximum stud spacing (inches) | Minimum nail | Nail penetration (inches) | Edge spacing (inches o.c.) | Field spacing (inches o.c.) |
|---|---|---|---|---|---|---|
| 3/8 | 24/0 | 16 | 6d common (2.0 x 0.113 inch) | 1.5 | 6 | 12 |
| 7/16 | 24/16 | 16 | 8d common (2.5 x 0.131 inch) | 1.75 | 6 | 12 |
| 7/16 | 24/16 | 24 | 8d common (2.5 x 0.131 inch) | 1.75 | 6 | 12 |
The span rating is printed on the grade stamp, so check it before trusting thickness alone: the table limits a 24/0 panel to 16 inch studs even though 24/16 is allowed at 24 inches. Panels rated Wall-16 or Wall-24 are allowed as an alternate to 24/0, and plywood siding rated 16 o.c. or 24 o.c. is allowed as an alternate to 24/16. Wall-16 and 16 o.c. plywood siding are limited to studs at no more than 16 inches on center (footnote c).
The table does not give a single "minimum wall sheathing thickness" for every house. It gives rows that combine thickness, nail and spacing, and then ties each row to a wind speed.
OSB vs plywood wall sheathing
The IRC treats OSB and plywood the same way: both are wood structural panels under Section R604, and Table R602.3(3) is read by span rating and thickness. A 7/16 inch 24/16 OSB panel and a 7/16 inch 24/16 plywood panel with a matching grade mark sit in the same row.
One plywood detail appears in the footnotes. Three-ply plywood sheathing on studs spaced more than 16 inches on center must be applied with the panel strength axis perpendicular to the supports (footnote a). With a 24 inch layout that means the long face grain runs across the studs, not along them.
Moisture behaviour, weight and cost are product questions, not code questions. The grade mark is what the inspector checks.
What wind speed does wall sheathing handle?
Table R602.3(3) also lists the maximum ultimate design wind speed (Vult) for each row, by exposure category. Find your site's design wind speed and exposure on your jurisdiction's wind map and local amendments, then check that the row you are using covers it.
2021 IRC Table R602.3(3), maximum ultimate design wind speed (mph) by wind exposure category.
| Panel | Stud spacing (inches) | Exposure B | Exposure C | Exposure D |
|---|---|---|---|---|
| 3/8 inch, 24/0, 6d common | 16 | 140 | 115 | 110 |
| 7/16 inch, 24/16, 8d common | 16 | 170 | 140 | 135 |
| 7/16 inch, 24/16, 8d common | 24 | 140 | 115 | 110 |
Two patterns stand out. Moving from 16 to 24 inch studs with the 7/16 inch panel drops each limit to the values listed for the 3/8 inch panel at 16 inches. And exposure matters: for the same panel and spacing, Exposure B allows a higher wind speed than Exposure C or D.
Footnote b states that the table is based on wind pressures acting toward and away from building surfaces under Section R301.2, and that lateral bracing requirements follow Section R602.10. That is the boundary of this article. Braced wall panels, the bracing methods and the sheathing nailing they require are in R602.10 and are not repeated here. For how those panels sit in the wall layout, see wall framing basics.
Wall sheathing nailing schedule
Fastener size and spacing for wall panels come from Table R602.3(3) (above) or from the general fastening schedule, Table R602.3(1).
2021 IRC Table R602.3(1), wood structural panels, subfloor, roof and interior wall sheathing to framing (wall use shown).
| Panel thickness (inch) | Fastener for wall use | Edges (inches o.c.) | Intermediate supports (inches o.c.) |
|---|---|---|---|
| 19/32 to 3/4 | 8d common (2-1/2 x 0.131 inch), or deformed 2-3/8 x 0.113 x 0.266 inch head | 6 | 12 |
| 7/8 to 1-1/4 | 10d common (3 x 0.148 inch), or deformed (2-1/2 x 0.131 x 0.281 inch head) | 6 | 12 |
Notes on reading the schedule:
- The heading of that block of Table R602.3(1) says it covers interior wall sheathing and subfloor and roof sheathing, and points readers to Table R602.3(3) for exterior wall panels resisting wind. For 3/8 to 1/2 inch panels, read the 6d row directly in Table R602.3(1), and use Table R602.3(3) for exterior walls.
- Nails must be spaced at no more than 6 inches on center at all supports where spans are 48 inches or greater (footnote c).
- Fasteners not covered by the table follow Table R602.3(2), the alternate attachments table.
For subfloor panels in the same schedule, see subfloor thickness. Roof panels, which share the table but have different span ratings and ring-shank options, are in roof sheathing thickness.
Can wall sheathing be something other than OSB or plywood?
Yes. The fastening schedule also lists other wall sheathing products, and the footnotes name their standards.
2021 IRC Table R602.3(1), other wall sheathing. Spacing in inches on center.
| Material | Fastener | Edges | Intermediate supports |
|---|---|---|---|
| 1/2 inch structural cellulosic fiberboard | 1-1/2 x 0.120 inch galvanized roofing nail, 7/16 inch head, or 1-1/4 inch 16 gauge staple | 3 | 6 |
| 25/32 inch structural cellulosic fiberboard | 1-3/4 x 0.120 inch galvanized roofing nail, 7/16 inch head, or 1-1/4 inch 16 gauge staple | 3 | 6 |
| 1/2 inch gypsum sheathing | 1-1/2 x 0.120 inch galvanized roofing nail, or galvanized staple, or 1-1/4 inch Type W or S screws | 7 | 7 |
| 5/8 inch gypsum sheathing | 1-3/4 x 0.120 inch galvanized roofing nail, or galvanized staple, or 1-1/4 inch Type W or S screws | 7 | 7 |
Gypsum sheathing must conform to ASTM C1396 and be installed in accordance with ASTM C1280 or GA 253, and fiberboard sheathing must conform to ASTM C208 (footnote g). Four-foot by 8-foot or 4-foot by 9-foot panels must be applied vertically (footnote d).
Particleboard wall sheathing has its own table. Table R602.3(4) lists 3/8 inch M-1 exterior glue and 1/2 inch M-2 exterior glue, both for studs at 16 inches on center where siding is nailed to studs. Where siding is nailed to the sheathing, the 3/8 inch grade has no listed value and the 1/2 inch grade is listed at 16 inches. The footnote limits it to wall sheathing not exposed to the weather and calls for a 1/16 inch gap between panels and nails at least 3/8 inch from panel edges.
Board sheathing on walls follows items 20 and 21 of Table R602.3(1).
Where does the water-resistive barrier go?
Section R703.2 requires at least one layer of water-resistive barrier over studs or sheathing on all exterior walls, continuous to the top of the wall. It is a separate layer from the structural sheathing. No. 15 asphalt felt and ASTM E2556 barriers are lapped at least 2 inches horizontally and 6 inches at joints. Check local amendments to Section R703.1 before relying on the base text.
Wall sheathing on a framing plan
Sheathing is rarely drawn on a floor framing plan, but the wall schedule or general notes should state the panel thickness, span rating, nail size and edge and field spacing, along with the design wind speed and exposure the choice was made for. That lets a reviewer check the same row you used. Stud spacing is a shared input: a 24 inch layout changes the panel row and the wind limits above, so confirm it against stud spacing before specifying a 3/8 inch panel.
For corners, openings and the base of the wall, see California corner framing, the header size chart, the sill plate guide and hurricane ties.
Summary
Under the 2021 IRC, exterior wall sheathing is fastened directly to the studs and must meet Table R602.3(3) where it resists wind pressure. That table allows 3/8 inch (24/0) panels on 16 inch studs and 7/16 inch (24/16) panels on 16 or 24 inch studs, each nailed at 6 inches on center at edges and 12 inches in the field, with wind speed limits by exposure. OSB and plywood are both wood structural panels. Braced wall panels follow Section R602.10, and the adopted code and local amendments govern.
Framing Plan is a preliminary drawing aid that draws joist layouts, beams and openings and exports PNG, PDF and DXF. It does not check wall sheathing against the IRC, so copy the table row you use into your drawing notes. Open the framing studio to lay out the framing that the sheathing covers.