Rev 01.29.21

This is a partial list of common code items. These requirements do not imply approval of any construction that does not comply with the current International Residential Code (IRC) and International Building Code (IBC).

Except as noted, all references are to the Washington state amended International Residential Code and International Building Code (IBC).

The approved plans and permit/inspection card shall be on the job site at the time of all inspections.

Footing

• Assumed soil bearing pressure is 1500 PSF. (Table R401.4.1)
• Frost protection is 12 inches for footings. (R403.1.1)
• Spread footings shall be at least 6 inches and footing projections shall be at least 2 inches and shall not exceed the thickness of the footing. (R403.1.1)
• Footing sizes shall be minimum width and depth. (R403 and Table 403.1.)
  • 1 story:    12” wide x 6” thick
  • 2 story:    15” wide x 6” thick
  • 3 story:    23” wide x 6” thick
• Continuous #4 rebar required 3 inches clear from bottom of footing. (R403.1.3)

Foundation

• Stem wall within Seismic Design Category D1 shall comply with the following:

1. Minimum reinforcement shall consist of one #4 horizontal bar located in the upper 12 inches of the wall.
2. Height of unbalanced backfill shall not exceed 4 feet. (R404.1.4)
3. Foundation walls supporting more than 4 feet of unbalanced backfill shall be constructed in accordance with Table R404.1.(2) (1 through 9).

• Seismic reinforcing in Design Category D1 where a construction joint is created between the footing and stem wall shall be provided one #4 vertical bar four foot on-center extending 14 inches into the stem wall and at least 3 inches clear from the bottom of footing. (R403.1.3.1)
• Anchor bolt shall be ½ x 10” and spaced a maximum of 6 feet on-center and within 12 inches from the end of plates and a minimum of two bolts per plate. Plate washers shall be a 3 x 3 x ¼ at braced wall lines and permitted to be slotted 3/16” x 1 ¾” where cut washers are used between plate and nut. Interior bearing walls shall be anchored to a footing. (R403.1.6.1 and R602.11.2)
• The maximum anchor bolt spacing to be 4 feet on-center for buildings over two stories in height. (R403.1.6.1)
• Foundation ventilation shall be 1 square foot of ventilation per 300 square feet of under floor area. (R408.2)
• Unvented crawl spaces are prohibited. (Appendix F-101.1)
• Venting in flood plains shall be at least 1 square inch per 1 square foot of enclosed area. (R322.2.2)
• Provisions shall be made for the control and drainage of surface water away from the building. The grade shall slope a minimum of 6 inches in 10 feet away from the building. (R401.3)
• Drains shall be provided around all foundations that retain earth and enclosed habitable or usable spaces located below grade. (R405.1)
• Potential radon routes shall be closed in accordance with Sections AF103.2.1 through AF103.2.8 Reference 
  Standards of the IRC. Minimum requirements include a 3–4 inch “T” fitting inserted beneath the soil-gas-vapor retarder and connected to a vent pipe extending through the conditioned space terminating not less than 12 inches above the roof at least 10 feet from any window or other vent penetration.
• Provide ground cover of 6-mil polyethylene or equivalent in crawl space. (AF103.3)

Floors

• Wood in contact with concrete shall be pressure treated or natural durable wood. (R317.1 #2)
• Fasteners for pressure preservative-treated wood (ACQ) shall be of hot-dipped zinc-coated galvanized steel, silicon bronze or copper. (R317.3.1)
• Minimum clearance of 12 inches under beams and 18 inches under joist is required in crawl spaces or the wood is required to be pressure treated or decay resistant. (R317.1 #1)
• Joists, beams, or girders shall bear 1.5 inches on wood and 3 inches on masonry or concrete. (R502.6)
• Decks shall be positively anchored to structures with lags. (R502.2)
• Joists shall be laterally supported at intermediate bearing with rotation blocking. (R502.7 Exception #2)
• Joists, beams or girders entering into concrete shall be P.T. and a half-inch air space around ends, sides, and tops. (R317.1(4))
• Crawl access shall be provided at a minimum of 18 x 24 inches. (R408.4)
• See details for notching and boring of joists available from Clark County.

Walls

• Wood framing subject to water splash shall be protected by approved methods (elevated 2 inches above concrete or 6 inches above grade) or approved materials (P.T. wood or natural decay resistant wood). (R317.1 #5)
• Wood framing that rests on concrete and is less than 8 inches from the exposed ground shall be pressure treated or natural durable wood. (R317.1 #2)
• Interior load bearing walls shall be framed as exterior walls. (R602.4)
• Studs shall have full bearing on a nominal 2-by or larger or sill plate having a width at least equal to the width of the studs. (R602.3.4)
• Spacing between braced wall lines in each story shall not exceed 25 feet on center in both the longitudinal and transverse directions. (R602.10.2.2)
• Fire blocking shall be provided to cut off all concealed draft openings and to form an effective fire barrier between stories and between a top story and the roof space.

1. Vertically at the ceiling and floor level and horizontally at intervals not exceeding 10 feet.
2. In concealed spaces between stair stringers at the top and bottom of run.
3. At all interconnections between concealed vertical and horizontal spaces such as those that occur at soffits, drop ceilings, and cove ceilings.
4. At openings around vents, pipes, and ducts at ceiling and floor level, with an approved material to resist the free passage of flame and products of combustion. (R302.11)
5. See details for notching and boring of joists available from Clark County or IRC referenced details.

Roof Framing

• Rafters shall be provided full bearing on the ridge board the depth of the cut rafter. (R802.3)
• Hips and valley rafters shall be supported at the ridge by a brace to a bearing partition or designed to carry the specified loads. (R802.3)
• Rafters and ceiling joist exceeding a ratio of 5:1 (2x10) shall be laterally supported (blocked) at bearing points. (R802.8)
• Rafters and trusses shall be provided with approved connectors to resist uplifts. (R802.11)
• A continuous load path shall be provided to transmit the uplift forces from the rafter or truss ties to the foundation. (R802.11.1)

Roofs

• Composition roof shingles must be a minimum of 25-year life shingles manufactured to ASTM 3462 and installed per the manufacturer’s installation specifications.
• Attic ventilation must be 1/150th of the attic area or 1/300th of attic area if at least 50 percent but not more than 80 percent of the required ventilation is 3 feet above the eave or cornice vents, or provide a moisture barrier not exceeding one perm on the warm-in-winter side of the ceiling. (R806.2)
• Provide a readily accessible attic opening to all areas with 30 square feet or more and 30 inches or more of vertical height. The rough framed opening shall be not less than 22 x 30 inches with a minimum of 30 inches of headroom provided at some point above the opening. (R807)
• New roof coverings shall not be installed without first removing the existing roof if two layers already exist. (R907.3)

Light / Ventilation

• Natural light shall provide the habitable spaces not less than 8 percent of which half shall be operable for ventilation. (R303.1)
• Mechanical provisions may be provided to substitute the natural ventilation requirements.
• Artificial light can be substituted for glazed area provided it is capable of producing an average illumination of 6-foot candles over the area of the room at a height of 30 inches above the floor level. (R303.1)
• Provide mechanical ventilation in bathrooms, laundry rooms (50 cfm at .25 WG) and kitchens (100 cfm at .25 WG). (M1507.4)
• Outside air is required to be supplied to each habitable room. (M1507.3.3)
• Whole house ventilation system required with a sone rating of 1.0 or integrated force-air ventilation system option. (M1507.3.4.2)
• All exhaust ducts in unconditioned spaces shall be insulated to R-8. (R403.2.1)