// CODE SNIPPET
Section R502 Wood Floor Framing
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Wood and wood-based products used for load-supporting purposes shall conform to the applicable provisions of this section.
Sawn lumber shall be identified by a grade mark of an accredited lumber grading or inspection agency and have design values certified by an accreditation body that complies with DOC PS 20. In lieu of a grade mark, a certificate of inspection issued by a lumber grading or inspection agency meeting the requirements of this section shall be accepted.
Preservative treated dimension lumber shall be identified as required by Section R317.2.
Approved end-jointed lumber identified by a grade mark conforming to Section R502.1.1 shall be permitted to be used interchangeably with solid-sawn members of the same species and grade. End-jointed lumber used in an assembly required elsewhere in this code to have a fire-resistance rating shall have the designation "Heat-Resistant Adhesive" or "HRA" included in its grade mark.
Structural capacities and design provisions for prefabricated wood I-joists shall be established and monitored in accordance with ASTM D5055.
Glued laminated timbers shall be manufactured and identified as required in ANSI A190.1, ANSI 117 and ASTM D3737.
Structural log members shall comply with the provisions of ICC 400.
Structural capacities for structural composite lumber shall be established and monitored in accordance with ASTM D5456.
Cross-laminated timber shall be manufactured and identified as required by ANSI/APA PRG 320.
Engineered wood rim boards shall conform to ANSI/APA PRR 410 or shall be evaluated in accordance with ASTM D7672. Structural capacities shall be in accordance with ANSI/APA PRR 410 or established in accordance with ASTM D7672. Rim boards conforming to ANSI/APA PRR 410 shall be marked in accordance with that standard.
Floors shall be designed and constructed in accordance with the provisions of this chapter, Figure R502.2 and Sections R317 and R318 or in accordance with ANSI AWC NDS.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
FLOOR CONSTRUCTION
A load path for lateral forces shall be provided between floor framing and braced wall panels located above or below a floor, as specified in Section R602.10.8.
Blocking for fastening panel edges or fixtures shall be not less than utility grade lumber. Subflooring shall be not less than utility grade lumber, No. 4 common grade boards or wood structural panels as specified in Section R503.2. Fireblocking shall be of any grade lumber.
Spans for floor joists shall be in accordance with Tables R502.3.1(1) and R502.3.1(2). For other grades and species and for other loading conditions, refer to the AWC STJR.
Table R502.3.1(1) shall be used to determine the maximum allowable span of floor joists that support sleeping areas and attics that are accessed by means of a fixed stairway in accordance with Section R311.7 provided that the design live load does not exceed 30 pounds per square foot (1.44 kPa) and the design dead load does not exceed 20 pounds per square foot (0.96 kPa). The allowable span of ceiling joists that support attics used for limited storage or no storage shall be determined in accordance with Section R802.5.
FLOOR JOIST SPANS FOR COMMON LUMBER SPECIES (Residential sleeping areas, live load = 30 psf, L/Δ = 360)a
| JOIST SPACING (inches) | SPECIES AND GRADE | DEAD LOAD = 10 psf | DEAD LOAD = 20 psf | |||||||
| 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | |||
| Maximum floor joist spans | ||||||||||
| (ft. - in.) | (ft. - in.) | (ft. - in.) | (ft. - in.) | (ft. - in.) | (ft. - in.) | (ft. - in.) | (ft. - in.) | |||
| 12 | Douglas fir-larch | SS | 12-6 | 16-6 | 21-0 | 25-7 | 12-6 | 16-6 | 21-0 | 25-7 |
| Douglas fir-larch | #1 | 12-0 | 15-10 | 20-3 | 24-8 | 12-0 | 15-7 | 19-0 | 22-0 | |
| Douglas fir-larch | #2 | 11-10 | 15-7 | 19-10 | 23-4 | 11-8 | 14-9 | 18-0 | 20-11 | |
| Douglas fir-larch | #3 | 9-11 | 12-7 | 15-5 | 17-10 | 8-11 | 11-3 | 13-9 | 16-0 | |
| Hem-fir | SS | 11-10 | 15-7 | 19-10 | 24-2 | 11-10 | 15-7 | 19-10 | 24-2 | |
| Hem-fir | #1 | 11-7 | 15-3 | 19-5 | 23-7 | 11-7 | 15-3 | 18-9 | 21-9 | |
| Hem-fir | #2 | 11-0 | 14-6 | 18-6 | 22-6 | 11-0 | 14-4 | 17-6 | 20-4 | |
| Hem-fir | #3 | 9-8 | 12-4 | 15-0 | 17-5 | 8-8 | 11-0 | 13-5 | 15-7 | |
| Southern pine | SS | 12-3 | 16-2 | 20-8 | 25-1 | 12-3 | 16-2 | 20-8 | 25-1 | |
| Southern pine | #1 | 11-10 | 15-7 | 19-10 | 24-2 | 11-10 | 15-7 | 18-7 | 22-0 | |
| Southern pine | #2 | 11-3 | 14-11 | 18-1 | 21-4 | 10-9 | 13-8 | 16-2 | 19-1 | |
| Southern pine | #3 | 9-2 | 11-6 | 14-0 | 16-6 | 8-2 | 10-3 | 12-6 | 14-9 | |
| Spruce-pine-fir | SS | 11-7 | 15-3 | 19-5 | 23-7 | 11-7 | 15-3 | 19-5 | 23-7 | |
| Spruce-pine-fir | #1 | 11-3 | 14-11 | 19-0 | 23-0 | 11-3 | 14-7 | 17-9 | 20-7 | |
| Spruce-pine-fir | #2 | 11-3 | 14-11 | 19-0 | 23-0 | 11-3 | 14-7 | 17-9 | 20-7 | |
| Spruce-pine-fir | #3 | 9-8 | 12-4 | 15-0 | 17-5 | 8-8 | 11-0 | 13-5 | 15-7 | |
| 16 | Douglas fir-larch | SS | 11-4 | 15-0 | 19-1 | 23-3 | 11-4 | 15-0 | 19-1 | 23-3 |
| Douglas fir-larch | #1 | 10-11 | 14-5 | 18-5 | 21-4 | 10-8 | 13-6 | 16-5 | 19-1 | |
| Douglas fir-larch | #2 | 10-9 | 14-2 | 17-5 | 20-3 | 10-1 | 12-9 | 15-7 | 18-1 | |
| Douglas fir-larch | #3 | 8-7 | 10-11 | 13-4 | 15-5 | 7-8 | 9-9 | 11-11 | 13-10 | |
| Hem-fir | SS | 10-9 | 14-2 | 18-0 | 21-11 | 10-9 | 14-2 | 18-0 | 21-11 | |
| Hem-fir | #1 | 10-6 | 13-10 | 17-8 | 21-1 | 10-6 | 13-4 | 16-3 | 18-10 | |
| Hem-fir | #2 | 10-0 | 13-2 | 16-10 | 19-8 | 9-10 | 12-5 | 15-2 | 17-7 | |
| Hem-fir | #3 | 8-5 | 10-8 | 13-0 | 15-1 | 7-6 | 9-6 | 11-8 | 13-6 | |
| Southern pine | SS | 11-2 | 14-8 | 18-9 | 22-10 | 11-2 | 14-8 | 18-9 | 22-10 | |
| Southern pine | #1 | 10-9 | 14-2 | 18-0 | 21-4 | 10-9 | 13-9 | 16-1 | 19-1 | |
| Southern pine | #2 | 10-3 | 13-3 | 15-8 | 18-6 | 9-4 | 11-10 | 14-0 | 16-6 | |
| Southern pine | #3 | 7-11 | 10-0 | 11-1 | 14-4 | 7-1 | 8-11 | 10-10 | 12-10 | |
| Spruce-pine-fir | SS | 10-6 | 13-10 | 17-8 | 21-6 | 10-6 | 13-10 | 17-8 | 21-4 | |
| Spruce-pine-fir | #1 | 10-3 | 13-6 | 17-2 | 19-11 | 9-11 | 12-7 | 15-5 | 17-10 | |
| Spruce-pine-fir | #2 | 10-3 | 13-6 | 17-2 | 19-11 | 9-11 | 12-7 | 15-5 | 17-10 | |
| Spruce-pine-fir | #3 | 8-5 | 10-8 | 13-0 | 15-1 | 7-6 | 9-6 | 11-8 | 13-6 | |
| 19.2 | Douglas fir-larch | SS | 10-8 | 14-1 | 18-0 | 21-10 | 10-8 | 14-1 | 18-0 | 21-4 |
| Douglas fir-larch | #1 | 10-4 | 13-7 | 16-9 | 19-6 | 9-8 | 12-4 | 15-0 | 17-5 | |
| Douglas fir-larch | #2 | 10-1 | 13-0 | 15-11 | 18-6 | 9-3 | 11-8 | 14-3 | 16-6 | |
| Douglas fir-larch | #3 | 7-10 | 10-0 | 12-2 | 14-1 | 7-0 | 8-11 | 10-11 | 12-7 | |
| Hem-fir | SS | 10-1 | 13-4 | 17-0 | 20-8 | 10-1 | 13-4 | 17-0 | 20-7 | |
| Hem-fir | #1 | 9-10 | 13-0 | 16-7 | 19-3 | 9-7 | 12-2 | 14-10 | 17-2 | |
| Hem-fir | #2 | 9-5 | 12-5 | 15-6 | 17-1 | 8-11 | 11-4 | 13-10 | 16-1 | |
| Hem-fir | #3 | 7-8 | 9-9 | 11-10 | 13-9 | 6-10 | 8-8 | 10-7 | 12-4 | |
| Southern pine | SS | 10-6 | 13-10 | 17-8 | 21-6 | 10-6 | 13-10 | 17-8 | 21-6 | |
| Southern pine | #1 | 10-1 | 13-4 | 16-5 | 19-6 | 9-11 | 12-7 | 14-8 | 17-5 | |
| Southern pine | #2 | 9-6 | 12-1 | 14-4 | 16-10 | 8-6 | 10-10 | 12-10 | 15-1 | |
| Southern pine | #3 | 7-3 | 9-1 | 11-0 | 13-1 | 6-5 | 8-2 | 9-10 | 11-8 | |
| Spruce-pine-fir | SS | 9-10 | 13-0 | 16-7 | 20-2 | 9-10 | 13-0 | 16-7 | 19-6 | |
| Spruce-pine-fir | #1 | 9-8 | 12-9 | 15-8 | 18-3 | 9-1 | 11-6 | 14-1 | 16-3 | |
| Spruce-pine-fir | #2 | 9-8 | 12-9 | 15-8 | 18-3 | 9-1 | 11-6 | 14-1 | 16-3 | |
| Spruce-pine-fir | #3 | 7-8 | 9-9 | 11-10 | 13-9 | 6-10 | 8-8 | 10-7 | 12-4 | |
| 24 | Douglas fir-larch | SS | 9-11 | 13-1 | 16-8 | 20-3 | 9-11 | 13-1 | 16-5 | 19-1 |
| Douglas fir-larch | #1 | 9-7 | 12-4 | 15-0 | 17-5 | 8-8 | 11-0 | 13-5 | 15-7 | |
| Douglas fir-larch | #2 | 9-3 | 11-8 | 14-3 | 16-6 | 8-3 | 10-5 | 12-9 | 14-9 | |
| Douglas fir-larch | #3 | 7-0 | 8-11 | 10-11 | 12-7 | 6-3 | 8-0 | 9-9 | 11-3 | |
| Hem-fir | SS | 9-4 | 12-4 | 15-9 | 19-2 | 9-4 | 12-4 | 15-9 | 18-5 | |
| Hem-fir | #1 | 9-2 | 12-1 | 14-10 | 17-2 | 8-7 | 10-10 | 13-3 | 15-5 | |
| Hem-fir | #2 | 8-9 | 11-4 | 13-10 | 16-1 | 8-0 | 10-2 | 12-5 | 14-4 | |
| Hem-fir | #3 | 6-10 | 8-8 | 10-7 | 12-4 | 6-2 | 7-9 | 9-6 | 11-0 | |
| Southern pine | SS | 9-9 | 12-10 | 16-5 | 19-11 | 9-9 | 12-10 | 16-5 | 19-8 | |
| Southern pine | #1 | 9-4 | 12-4 | 14-8 | 17-5 | 8-10 | 11-3 | 13-1 | 15-7 | |
| Southern pine | #2 | 8-6 | 10-10 | 12-10 | 15-1 | 7-7 | 9-8 | 11-5 | 13-6 | |
| Southern pine | #3 | 6-5 | 8-2 | 9-10 | 11-8 | 5-9 | 7-3 | 8-10 | 10-5 | |
| Spruce-pine-fir | SS | 9-2 | 12-1 | 15-5 | 18-9 | 9-2 | 12-1 | 15-0 | 17-5 | |
| Spruce-pine-fir | #1 | 8-11 | 11-6 | 14-1 | 16-3 | 8-1 | 10-3 | 12-7 | 14-7 | |
| Spruce-pine-fir | #2 | 8-11 | 11-6 | 14-1 | 16-3 | 8-1 | 10-3 | 12-7 | 14-7 | |
| Spruce-pine-fir | #3 | 6-10 | 8-8 | 10-7 | 12-4 | 6-2 | 7-9 | 9-6 | 11-0 | |
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
Note: Check sources for availability of lumber in lengths greater than 20 feet.
- Dead load limits for townhouses in Seismic Design Category C and all structures in Seismic Design Categories D0, D1 and D2 shall be determined in accordance with Section R301.2.2.2.
FLOOR JOIST SPANS FOR COMMON LUMBER SPECIES (Residential living areas, live load = 40 psf, L/Δ = 360)b
| JOIST SPACING (inches) | SPECIES AND GRADE | DEAD LOAD = 10 psf | DEAD LOAD = 20 psf | |||||||
| 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | |||
| Maximum floor joist spans | ||||||||||
| (ft. - in.) | (ft. - in.) | (ft. - in.) | (ft. - in.) | (ft. - in.) | (ft. - in.) | (ft. - in.) | (ft. - in.) | |||
| 12 | Douglas fir-larch | SS | 11-4 | 15-0 | 19-1 | 23-3 | 11-4 | 15-0 | 19-1 | 23-3 |
| Douglas fir-larch | #1 | 10-11 | 14-5 | 18-5 | 22-0 | 10-11 | 14-2 | 17-4 | 20-1 | |
| Douglas fir-larch | #2 | 10-9 | 14-2 | 18-0 | 20-11 | 10-8 | 13-6 | 16-5 | 19-1 | |
| Douglas fir-larch | #3 | 8-11 | 11-3 | 13-9 | 16-0 | 8-1 | 10-3 | 12-7 | 14-7 | |
| Hem-fir | SS | 10-9 | 14-2 | 18-0 | 21-11 | 10-9 | 14-2 | 18-0 | 21-11 | |
| Hem-fir | #1 | 10-6 | 13-10 | 17-8 | 21-6 | 10-6 | 13-10 | 17-1 | 19-10 | |
| Hem-fir | #2 | 10-0 | 13-2 | 16-10 | 20-4 | 10-0 | 13-1 | 16-0 | 18-6 | |
| Hem-fir | #3 | 8-8 | 11-0 | 13-5 | 15-7 | 7-11 | 10-0 | 12-3 | 14-3 | |
| Southern pine | SS | 11-2 | 14-8 | 18-9 | 22-10 | 11-2 | 14-8 | 18-9 | 22-10 | |
| Southern pine | #1 | 10-9 | 14-2 | 18-0 | 21-11 | 10-9 | 14-2 | 16-11 | 20-1 | |
| Southern pine | #2 | 10-3 | 13-6 | 16-2 | 19-1 | 9-10 | 12-6 | 14-9 | 17-5 | |
| Southern pine | #3 | 8-2 | 10-3 | 12-6 | 14-9 | 7-5 | 9-5 | 11-5 | 13-6 | |
| Spruce-pine-fir | SS | 10-6 | 13-10 | 17-8 | 21-6 | 10-6 | 13-10 | 17-8 | 21-6 | |
| Spruce-pine-fir | #1 | 10-3 | 13-6 | 17-3 | 20-7 | 10-3 | 13-3 | 16-3 | 18-10 | |
| Spruce-pine-fir | #2 | 10-3 | 13-6 | 17-3 | 20-7 | 10-3 | 13-3 | 16-3 | 18-10 | |
| Spruce-pine-fir | #3 | 8-8 | 11-0 | 13-5 | 15-7 | 7-11 | 10-0 | 12-3 | 14-3 | |
| 16 | Douglas fir-larch | SS | 10-4 | 13-7 | 17-4 | 21-1 | 10-4 | 13-7 | 17-4 | 21-1 |
| Douglas fir-larch | #1 | 9-11 | 13-1 | 16-5 | 19-1 | 9-8 | 12-4 | 15-0 | 17-5 | |
| Douglas fir-larch | #2 | 9-9 | 12-9 | 15-7 | 18-1 | 9-3 | 11-8 | 14-3 | 16-6 | |
| Douglas fir-larch | #3 | 7-8 | 9-9 | 11-11 | 13-10 | 7-0 | 8-11 | 10-11 | 12-7 | |
| Hem-fir | SS | 9-9 | 12-10 | 16-5 | 19-11 | 9-9 | 12-10 | 16-5 | 19-11 | |
| Hem-fir | #1 | 9-6 | 12-7 | 16-0 | 18-10 | 9-6 | 12-2 | 14-10 | 17-2 | |
| Hem-fir | #2 | 9-1 | 12-0 | 15-2 | 17-7 | 8-11 | 11-4 | 13-10 | 16-1 | |
| Hem-fir | #3 | 7-6 | 9-6 | 11-8 | 13-6 | 6-10 | 8-8 | 10-7 | 12-4 | |
| Southern pine | SS | 10-2 | 13-4 | 17-0 | 20-9 | 10-2 | 13-4 | 17-0 | 20-9 | |
| Southern pine | #1 | 9-9 | 12-10 | 16-1 | 19-1 | 9-9 | 12-7 | 14-8 | 17-5 | |
| Southern pine | #2 | 9-4 | 11-10 | 14-0 | 16-6 | 8-6 | 10-10 | 12-10 | 15-1 | |
| Southern pine | #3 | 7-1 | 8-11 | 10-10 | 12-10 | 6-5 | 8-2 | 9-10 | 11-8 | |
| Spruce-pine-fir | SS | 9-6 | 12-7 | 16-0 | 19-6 | 9-6 | 12-7 | 16-0 | 19-6 | |
| Spruce-pine-fir | #1 | 9-4 | 12-3 | 15-5 | 17-10 | 9-1 | 11-6 | 14-1 | 16-3 | |
| Spruce-pine-fir | #2 | 9-4 | 12-3 | 15-5 | 17-10 | 9-1 | 11-6 | 14-1 | 16-3 | |
| Spruce-pine-fir | #3 | 7-6 | 9-6 | 11-8 | 13-6 | 6-10 | 8-8 | 10-7 | 12-4 | |
| 19.2 | Douglas fir-larch | SS | 9-8 | 12-10 | 16-4 | 19-10 | 9-8 | 12-10 | 16-4 | 19-6 |
| Douglas fir-larch | #1 | 9-4 | 12-4 | 15-0 | 17-5 | 8-10 | 11-3 | 13-8 | 15-11 | |
| Douglas fir-larch | #2 | 9-2 | 11-8 | 14-3 | 16-6 | 8-5 | 10-8 | 13-0 | 15-1 | |
| Douglas fir-larch | #3 | 7-0 | 8-11 | 10-11 | 12-7 | 6-5 | 8-2 | 9-11 | 11-6 | |
| Hem-fir | SS | 9-2 | 12-1 | 15-5 | 18-9 | 9-2 | 12-1 | 15-5 | 18-9 | |
| Hem-fir | #1 | 9-0 | 11-10 | 14-10 | 17-2 | 8-9 | 11-1 | 13-6 | 15-8 | |
| Hem-fir | #2 | 8-7 | 11-3 | 13-10 | 16-1 | 8-2 | 10-4 | 12-8 | 14-8 | |
| Hem-fir | #3 | 6-10 | 8-8 | 10-7 | 12-4 | 6-3 | 7-11 | 9-8 | 11-3 | |
| Southern pine | SS | 9-6 | 12-7 | 16-0 | 19-6 | 9-6 | 12-7 | 16-0 | 19-6 | |
| Southern pine | #1 | 9-2 | 12-1 | 14-8 | 17-5 | 9-0 | 11-5 | 13-5 | 15-11 | |
| Southern pine | #2 | 8-6 | 10-10 | 12-10 | 15-1 | 7-9 | 9-10 | 11-8 | 13-9 | |
| Southern pine | #3 | 6-5 | 8-2 | 9-10 | 11-8 | 5-11 | 7-5 | 9-0 | 10-8 | |
| Spruce-pine-fir | SS | 9-0 | 11-10 | 15-1 | 18-4 | 9-0 | 11-10 | 15-1 | 17-9 | |
| Spruce-pine-fir | #1 | 8-9 | 11-6 | 14-1 | 16-3 | 8-3 | 10-6 | 12-10 | 14-10 | |
| Spruce-pine-fir | #2 | 8-9 | 11-6 | 14-1 | 16-3 | 8-3 | 10-6 | 12-10 | 14-10 | |
| Spruce-pine-fir | #3 | 6-10 | 8-8 | 10-7 | 12-4 | 6-3 | 7-11 | 9-8 | 11-3 | |
| 24 | Douglas fir-larch | SS | 9-0 | 11-11 | 15-2 | 18-5 | 9-0 | 11-11 | 15-0 | 17-5 |
| Douglas fir-larch | #1 | 8-8 | 11-0 | 13-5 | 15-7 | 7-11 | 10-0 | 12-3 | 14-3 | |
| Douglas fir-larch | #2 | 8-3 | 10-5 | 12-9 | 14-9 | 7-6 | 9-6 | 11-8 | 13-6 | |
| Douglas fir-larch | #3 | 6-3 | 8-0 | 9-9 | 11-3 | 5-9 | 7-3 | 8-11 | 10-4 | |
| Hem-fir | SS | 8-6 | 11-3 | 14-4 | 17-5 | 8-6 | 11-3 | 14-4 | 16-10a | |
| Hem-fir | #1 | 8-4 | 10-10 | 13-3 | 15-5 | 7-10 | 9-11 | 12-1 | 14-0 | |
| Hem-fir | #2 | 7-11 | 10-2 | 12-5 | 14-4 | 7-4 | 9-3 | 11-4 | 13-1 | |
| Hem-fir | #3 | 6-2 | 7-9 | 9-6 | 11-0 | 5-7 | 7-1 | 8-8 | 10-1 | |
| Southern pine | SS | 8-10 | 11-8 | 14-11 | 18-1 | 8-10 | 11-8 | 14-11 | 18-0 | |
| Southern pine | #1 | 8-6 | 11-3 | 13-1 | 15-7 | 8-1 | 10-3 | 12-0 | 14-3 | |
| Southern pine | #2 | 7-7 | 9-8 | 11-5 | 13-6 | 7-0 | 8-10 | 10-5 | 12-4 | |
| Southern pine | #3 | 5-9 | 7-3 | 8-10 | 10-5 | 5-3 | 6-8 | 8-1 | 9-6 | |
| Spruce-pine-fir | SS | 8-4 | 11-0 | 14-0 | 17-0 | 8-4 | 11-0 | 13-8 | 15-11 | |
| Spruce-pine-fir | #1 | 8-1 | 10-3 | 12-7 | 14-7 | 7-5 | 9-5 | 11-6 | 13-4 | |
| Spruce-pine-fir | #2 | 8-1 | 10-3 | 12-7 | 14-7 | 7-5 | 9-5 | 11-6 | 13-4 | |
| Spruce-pine-fir | #3 | 6-2 | 7-9 | 9-6 | 11-0 | 5-7 | 7-1 | 8-8 | 10-1 | |
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
Note: Check sources for availability of lumber in lengths greater than 20 feet.
- End bearing length shall be increased to 2 inches.
- Dead load limits for townhouses in Seismic Design Category C and all structures in Seismic Design Categories D0, D1, and D2 shall be determined in accordance with Section R301.2.2.2.
Table R502.3.1(2) shall be used to determine the maximum allowable span of floor joists that support other areas of the building, other than sleeping rooms and attics, provided that the design live load does not exceed 40 pounds per square foot (1.92 kPa) and the design dead load does not exceed 20 pounds per square foot (0.96 kPa).