New Hampshire

Statewide summary — confirm with your building department before designing

Ground snow load corrected from 50 to 70 psf, and the min and max columns are now filled from the table New Hampshire has actually adopted. New Hampshire does not leave ground snow load to each town the way it leaves the rest of Table R301.2. Amendment RE-24-01-25 rewrites note o to IRC Table R301.2 to require that the jurisdiction fill in the ground snow load using Table 1 of Ground Snow Loads for New Hampshire, ERDC/CRREL TR-02-6. That is a February 2002 report of the US Army Corps of Engineers Cold Regions Research and Engineering Laboratory, produced with the Structural Engineers of New Hampshire, and the state amendment makes it binding by reference rather than advisory. Table 1 of that report gives a ground snow load for each of the 259 New Hampshire towns at one stated elevation. The values run from 50 psf to 120 psf. 50 psf applies in twenty seacoast and lower Merrimack valley towns including Hampton, Hampton Falls, North Hampton, New Castle, Greenland, Newington, Exeter, Kensington, East Kingston, Kingston and Newmarket. 120 psf applies at Beans Purchase, Chandlers Purchase and Thompson and Meserves Purchase in the White Mountains, with Jackson, Pinkhams Grant and Sargents Purchase at 115 psf. The stored 50 psf was the statewide floor and understated the capital: Concord and Manchester are 70 psf, Nashua is 60 psf, Portsmouth area towns are 50 to 55 psf, Berlin, Bartlett, Gorham and Jefferson are 100 psf. 70 psf is the value the adopted table assigns to Concord and Manchester and is used here as the representative figure only; it is not a substitute for the town value and it is below the adopted value for most of the state, since the median across the 259 towns is 80 psf. Two features of the adopted table mean this range is not the whole picture. Each tabulated value applies only at the elevation printed beside it and must be adjusted by 2.1 psf for every 100 feet of elevation difference, so the number for a given lot depends on where on the hillside it sits. Above 2,500 feet the report directs that its data not be used and that a site-specific snow load case study be conducted instead. New Hampshire therefore publishes no upper bound at all for its highest terrain, and 120 psf is the top of the tabulated range rather than the worst case in the state. Note o was amended for the IRC only; the state does not amend IBC Section 1608.2, so the commercial side runs on the model code and its referenced ASCE 7 map, which shows case study areas across the White Mountains. The seismic design category correction from B to C made by the earlier audit stands. Checked against the USGS ASCE 7-16 design maps at Site Class D and Risk Category II, the short-period design acceleration at Manchester, Nashua and Concord all fall in the C band; Berlin and the far north compute to B, so C is conservative there rather than wrong. Nothing else on this row was changed. Frost depth 48 inches, wind speed 105 mph and winter design temperature -10 F are still not confirmed against any adopted New Hampshire table, because the state amendments fill in only the snow cell and leave the rest of Table R301.2 to each jurisdiction. One thing this row does not yet reflect: the amendments effective July 1, 2026 move six of the model codes, including the IBC and IRC, to their 2024 editions, so the 2021 editions recorded on this row are out of date as of that date. RSA 155-A:1, IV should be checked before relying on the edition fields.