Vermont's HOME Act makes an attached ADU by-right for owner-occupied homes; the unit is built to the state Fire & Building Safety Code, engineered for heavy snow.
Building approval
VT Division of Fire Safety
Program
Vermont Fire & Building Safety Code — State insignia/seal program
ADU law
HOME Act (S.100 / Act 47, 2023) (statewide)
ADU summary
One attached/internal ADU by-right for owner-occupied SF homes; detached may need approval.
Site / structural drivers
Heavy Green Mountains snow + cold
Verdict
Attached ADU by-right
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General information, current as of 2026 — not legal advice. Confirm specifics with your local jurisdiction.
An attached or internal one, yes. Vermont's HOME Act (S.100 / Act 47, 2023) requires all localities to allow one attached or internal ADU by-right for each owner-occupied single-family dwelling, as long as there's adequate wastewater capacity, the ADU is no more than 30% of the principal dwelling's floor area, it's outside flood-hazard/fluvial-erosion areas, and it meets local setback, coverage and parking standards. Detached ADUs, or ones requiring expanded parking, can still be subject to discretionary local approval.
The Vermont Fire & Building Safety Code (the 2025 edition is current), administered by the Department of Public Safety's Division of Fire Safety, which adopts and amends national model codes for Vermont conditions. Modular units are built to that code; commercial and multi-unit projects receive Division of Fire Safety plan review. Your local jurisdiction handles the site work — foundation, utilities, zoning.
Often yes, but it may not be fully by-right. The HOME Act's by-right guarantee is specifically for attached or internal ADUs on owner-occupied lots; a detached ADU can still require discretionary local approval. Many towns do allow detached ADUs — check your municipality's bylaw.
Snow, decisively. The Green Mountains and the Northeast Kingdom carry heavy ground-snow loads that dominate roof and structural design, and a high-performance thermal envelope is essential for Vermont winters. Seismic risk is low. PSL Modular engineers the snow load and envelope from your site coordinates.
Strongly. Resort towns like Stowe, Killington, and Sugarbush face severe workforce-housing shortages and short construction seasons. Modular units are built indoors year-round and set quickly, and multi-unit orders run in parallel with site prep — ideal for the mountain calendar.
PSL Modular units are permittable in all 50 states. Pick yours for the building-approval path, the ADU law, and the structural spec your site needs.