Description of the appropriate use of the table, including all assumptions and limitations. Provide references to applicable code sections

Description of Tables These tables are used to determine thickness of sheathing and spacing of supports based on material used and loading. Both of the tables are used together, the first table gives minimum thickness regardless of load and the second table gives span and thickness

information for different applied loads. The two tables you will need to use is Table 2304.7(1) Allowable spans for lumber floor and

roof sheathing and Table 2304.7(3) Allowable spans and loads for wood structural panel sheathing and single-floor grades continuous

over two or more spans with strength axis perpendicular to supports.

Example of Perpendicular Installation



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Text Box
Sheathing Table Design Aid (Example)


Definitions Subfloor: the layer of wood material that is installed on top of the floor joists to provide a surface that the floor will be installed on.

Floor Sheathing: 4 foot by 8 foot plywood boards with varying thickness laid out on and nailed to floor joists.

Diagonal Subfloor Boards: square-edged or tongue-and-groove, no longer than eight inches wide and no less than 25/32 inch thick.

Joist Spacing: the distance between each floor joist.

Species Group 1: Apitong, American Beech, Birch, Douglas-Fir 1, Kapur, Keruing, Western Larch, Sugar Maple, Pine, Southern

Pine, Tanoak

Species Group 2: Port Orford Cedar, Cypress, Douglas-Fir 2, Fir, Western Hemlock, Lauan, Black Maple, Mengkulang, Red Meranti,

Mersawa, Pine, Sweetgum, Tamarach, Yellow-Poplar

Species Group 3: Red Alder, Paper Birch, Alaska Cedar, Subalpine Fir, Eastern Hemlock, Bigleaf Maple, Pine, Redwood, Spruce

Species Group 4: Apsen, Cativo, Cedar, Cottonwood, Pine


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How to Use Table 2304.7 (1)- Lumber



Perpendicular to supports

Diagonally to Supports

Surfaced Dry

Surfaced Unseasoned

24” Span= 3/4” Floor

or 5/8” Roof

16” Span= 5/8” Floor

24” Span= 25/32” Floor

or 11/16″Roof

16” Span= 11/16” Floor

Surfaced Dry

Surfaced Unseasoned

24” Span= 3/4” Floor and Roof

16” Span= 5/8” Floor

24” Span= 25/32” Floor

or 25/32″Roof

16” Span= 11/16” Floor

Choose either Sheathing Grades

or Single Floor Grades

Choose Panel Span Rating and Panel


Choose whether sheathing is for

Roof or Floor

How to Use Table 2304.7 (3)- Plywood

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Table 2304.7 (1)

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Table 2304.7 (3)

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Example Problem Question: What is the minimum thickness of sheathing required for a 16” that is diagonally to supports and is surface unseasoned for a floor? Answer: First, look at table 2304.7 (1). Second, look at the column labeled diagonally to support. Third, look at the column under diagonally to supports, labeled surfaced unseasoned. Last, look at the row under the span column labeled 16”, and look at the number at the end of the row that corresponds with the 3rd step. Answer is 11/16.

Exercises Question: What is the minimum thickness of sheathing required for a 24” that is perpendicular to supports and is surfaced dry for a roof? Answer: 5/8 Question: What is the maximum span without edge support, and what is the total load of a roof with a 32/16 span? Answer: Either 15/32”, ½”, 5/8”, for the panel thickness. 28” for maximum span without edge support, and 40 psf for the total load.


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References 




 2312.NAU-PSSIS/Resources/Wood%20Design/2304.7%281%29.jpg



 IBC 2006, 220-SEC1-2312.NAU-PSSIS/Resources/Wood%20Design/cm220-IBC-2006-wood.pdf



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