Delaware

Statewide summary — confirm with your building department before designing

SNOW LOAD AUDIT, 2026. Ground snow load corrected from 15 to 25 psf and ultimate design wind speed corrected from 110 to 115 mph, because 15 psf and 110 mph are below every figure any Delaware government has actually adopted. snow_load_min_psf and snow_load_max_psf are left null. Start with the structural fact, because it governs everything else on this row: Delaware has no statewide building code. Title 16 Del. C. section 7601 provides that "The Levy Court of Kent County and the County Councils of New Castle County and Sussex County may adopt and enforce building codes, plumbing codes, electrical codes or other similar codes," and section 7602 imposes only a statewide minimum tied to the most recent IECC, plus zero-net-energy-capable targets. There is no Delaware residential code, no state Table R301.2 and no state snow map. A single "Delaware ground snow load" does not exist as a legal object. What exists is three county codes and the municipal codes beneath them, and the number that governs your lot comes from one of those. Two Delaware figures were found and they conflict; both are recorded here. Kent County has adopted the 2018 IRC and filled in the table itself at Kent County Code section 105-24, Amendment B(1), "Table R301.2(1), Climate and Geographic Design Criteria": ground snow load 25 lb/sq ft, wind design speed 115 mph, topographic effects no, special wind region no, wind-borne debris zone no, seismic design category A, weathering severe, frost line depth 24 inches, termite yes, winter design temperature 18 F, ice barrier underlayment not required, air freezing index 596, mean annual temperature 54 F. New Castle County's published one- and two-family dwelling plan review checklist instead carries the rafter design line "Ground snow load/LL = 20psf." Both are county government documents. The 25 psf was used for this row because it appears in an adopted county code as an explicit Table R301.2(1) entry, whereas the New Castle figure appears only in a plan review checklist and is written as a combined snow-or-live-load value for selecting rafter spans; 25 psf is also the higher of the two, so it does not under-design a Kent County site. Sussex County adopted the 2021 IRC and the 2021 IBC on 9 August 2022 by Ordinance 2851, Chapter 52 of the Sussex County Code, but that chapter adopts the model code by edition and does not reproduce Table R301.2(1). No Sussex ground snow load was located. Two counties out of three, with no state figure at all, is not a statewide range, which is why min and max are null. Wind speed is corrected from 110 to 115 mph. The stored 110 was an ASCE 7-16 map read for inland northern Delaware, and an adopted county code outranks a map read: Kent County requires 115. Even so, 115 does not cover the coast. Sussex County wind design is higher along the Atlantic, and the earlier audit recorded a Sussex range of roughly 105 to 140 mph depending on location and risk category, which was not re-verified in this pass. A Sussex site must take the county number. Seismic design category also conflicts, and both readings are kept. Kent County adopted A. This row carries B, which came from the USGS ASCE 7-16 design maps service at Site Class D and Risk Category II, where the short-period design spectral acceleration is about 0.19 g at Wilmington and Newark and about 0.17 g at Middletown, all in the B band, while Dover is about 0.14 g and the Sussex beaches about 0.11 g, which are A. B was kept because New Castle County holds a majority of the state population, and because the IRC exempts detached one- and two-family dwellings in categories A, B and C from its seismic provisions, so this is a labelling choice that does not by itself add a requirement to a typical house. A Kent County project should use the county's adopted A. Frost depth of 24 inches is confirmed and unchanged: it matches Kent County's adopted Table R301.2(1) exactly, and it matches the Sussex County minimum footer depth measured from final grade to the bottom of the footing. Termite risk of heavy corresponds to the compound moderate-to-heavy band of the IRC map and to Kent County's "yes." The winter design temperature on this row was not independently verified in this audit; Kent County adopts 18 F.