Oregon

Statewide summary — confirm with your building department before designing

No value on this row was changed by this audit. The seismic design category D was confirmed three ways: the City of Portland states category D1 for one and two family dwellings, Clackamas County publishes D, and the USGS ASCE 7-16 design maps at Site Class D and Risk Category II return D for Portland, Salem, Eugene and Medford. Two caveats matter. On the outer south coast around Coos Bay and Brookings the one-second ground motion exceeds the threshold that pushes a Risk Category II building to category E, which is above what this row shows. East of the Cascades the hazard is lower, with Bend and Pendleton computing to C and Ontario to B. The other numbers here cannot be carried by a scalar. Clackamas County adopts a 98 mph ultimate design wind speed at Risk Category II for the Portland metropolitan area and 120 mph inside a special wind region, against the 110 stored here, and the Oregon coast is a special wind region. Clackamas County sets frost depth by elevation at 12 inches below 2,500 feet, 18 inches from 2,500 to 4,000 feet and 24 inches above 4,000 feet, so the 18 stored here is too deep for Portland and too shallow for the Cascades. Portland's prescriptive roof snow load is 20 psf plus a rain on snow surcharge, while the Cascade crest is far above the 25 psf shown. The Building Codes Division publishes a statewide Design Criteria Hub that returns site-specific values by address, and it is the right place to look. Termite risk was not confirmed against an adopted Oregon table; treat the stored slight as unverified. 2026 snow-load pass. Oregon is a real state-adopted-source state and is the exception in this region. The 2023 Oregon Residential Specialty Code, the mandatory statewide residential code under OAR chapter 918, does not delegate ground snow load to the local building official and does not use the national IRC map: the ORSC records that IRC Figures R301.2(3) and R301.2(4), the model ground snow load maps, are not adopted. Instead Section R301.2.3.1 reads that site-specific ground snow loads, pg, shall be those set forth in the online lookup tool at Snowload.seao.org/lookup.html, with an elevation adjustment from Table R301.2.3.1 where the site sits above the modeled elevation. This is the same pattern as Utah: a professional-association product, the Structural Engineers Association of Oregon snow load study and its electronic map, is adopted by reference in the state instrument itself, which makes it usable here. Every one of the 36 counties in the ORSC Table R301.2 carries Note a in the ground snow load column, pointing to R301.2.3.1. snow_load_min_psf is set to 36 because R301.2.3.1 states that the minimum ground snow load for prescriptive design is 36 psf, a genuine statewide floor published by the state. Two readings of a minimum exist and both are recorded. The floor that the code imposes on prescriptive design is 36 psf, which is the figure used here because the ORSC is a prescriptive residential code. The raw modeled value the adopted tool returns can be well below that: the tool returns 9 psf for downtown Portland at 209 feet and 20 psf for Bend at 3,694 feet. Designers using nonprescriptive design are held instead to a minimum roof snow load of 25 psf, which is a roof quantity and not a ground quantity and must not be compared with the ground figures here. snow_load_max_psf is left null on purpose. The adopted lookup tool is a continuous model with no published statewide maximum, and sampling it cannot prove one. For scale only, and not as a maximum, the tool returns 683 psf at Timberline Lodge on Mount Hood at 5,938 feet and 378 psf at Crater Lake at 6,197 feet; Mount Hood rises to about 11,249 feet, far above any point sampled, so higher values certainly exist. A separate ORSC threshold is worth knowing: Section R301.2.3 sends buildings in regions with ground snow loads greater than 70 psf out of the prescriptive chapters and into accepted engineering practice. Ground snow load is corrected from 25 to 36 psf because 25 psf is below the state minimum for prescriptive design and is therefore not a lawful prescriptive value anywhere in Oregon. Wind speed is corrected from 110 to 103 mph. The figure 110 appears nowhere in Oregon Table R301.2; the adopted county basic design wind speeds run from 94 mph in Curry County to 103 mph in Baker and Wallowa counties, and 103 is the highest ordinary county value in the state instrument. Special wind regions are separate and reach 120 mph in the coastal and Columbia Gorge counties, so a coastal or Gorge site is governed by 120 rather than by this column. These are basic design wind speeds on the strength-level scale, the same scale as the value replaced. Frost depth of 18 inches is retained because it is a real value in the adopted table for Douglas, Crook, Deschutes, Jefferson, Jackson, Josephine and Multnomah counties, but the adopted range is 12 inches across the valley and coast counties and 24 inches across the severe-weathering counties east of the Cascades, and in Jackson, Josephine and Multnomah counties the depth drops to 12 inches below 2,500 feet. Seismic design category is unchanged; the adopted table carries Note c in that column, so Oregon delegates seismic design category to Section R301.2.2.1 rather than publishing it per county. One forward-looking caveat: the 2023 ORSC runs through March 31, 2027, and the 2026 ORSC review matrix rescinds the 36 psf prescriptive minimum and replaces it with 30 psf, rescinds the Oregon-specific Table R301.2.3.1 elevation adjustment, and moves determination to the Oregon Design Criteria Hub and the ASCE ground snow load geodatabase. The commercial 2025 OSSC already made that shift to ASCE 7-22 and has been mandatory statewide since April 1, 2026, but Statewide Alternate Method 26-01 lets ORSC users keep referencing the 2022 OSSC for nonprescriptive design during the 2023 ORSC period. Expect this row to need revisiting when the 2026 ORSC becomes mandatory.