Design Criteria: Residential

One- and Two- Family Dwellings and Townhouses

Effective January, 1 2021

Locally-Adopted Codes

2018 International Residential Code, Parts I-VI and IX, appendices A, B and G (with State amendments).

2018 International Energy Conservation Code (with Idaho State amendments)

2017 National Electrical Code (with State amendments)

2017 Idaho State Plumbing Code [website]

Other Criteria

  • Wind Speed: 115 mph gust velocity
  • Wind Exposure: “B” (“C” in some areas)
  • Seismic Design Category: “B” (IRC Structures Only-See Commercial Design Criteria for IBC)
  • Presumed Soil Bearing Pressure: 1500 psf without soils investigation
  • Frost Depth: 24 inches
  • Climate Zone: 5B
  • Snow load: Ground snow load 15 psf. Minimum uniformly distributed design roof load shall be 25 psf per local ordinance
  • Winter heating design temperature is 2 degrees (99% dry bulb)
  • Table R301.5 is amended to require a minimum uniform live load of 40 psf in habitable attics and sleeping rooms.
  • Foundations with stem walls shall be provided with a minimum of one # 4 bar at the top of the wall and one #4 bar at the bottom of the footing. #4 vertical bars are required at 6 feet on center.
  • Basement walls to have one #4 horizontal bar at 4 feet on center. One #4 bar is also required horizontally and vertically around openings, extending 2 feet beyond the opening. One #4 bar to be placed diagonally at corners of openings subject to cracking. Vertical bars installed per IRC.
  • Unvented fuel-burning appliances are not allowed.
  • 30” minimum crawl space depth measured from bottom of floor joist (per local resolution)

State-adopted Codes and Other Code Links

Idaho Division of Building Safety Statutes and Rules

Idaho State Fire Marshal (DOI)

Idaho Manufactured Home Installation Standards

ICC Free e-Codes