Box Elder County ADU rules by city
8 Box Elder County cities are covered. In 2 of them, detached backyard ADUs are generally allowed today. Each city sets its own lot size, parking and owner-occupancy rules, so check the city page before you design.
| City | County | Internal ADU | Detached ADU | Owner occupancy | S.B. 284 city | Checked |
|---|---|---|---|---|---|---|
| Brigham City | Box Elder | allowedno city lot minimum on file | allowedno city lot minimum on file | Required | Yes | ✓ 2026-09-24 |
| Tremonton | Box Elder | allowedno city lot minimum on file | allowedno city lot minimum on file | Required | Yes | ✓ 2026-09-24 |
| Perry | Box Elder | allowedno city lot minimum on file | allowed with conditionslot 11,000 sq ft+ | — | Yes | 2026-09-07 (not fully verified) |
| Garland | Box Elder | allowed with conditionsno city lot minimum on file | allowed only in limited casesno city lot minimum on file | — | No / unconfirmed | 2026-09-07 (not fully verified) |
| Willard | Box Elder | allowed with conditionsno city lot minimum on file | allowed only in limited casesno city lot minimum on file | — | No / unconfirmed | 2026-09-07 (not fully verified) |
| Honeyville | Box Elder | allowed with conditionsno city lot minimum on file | allowed only in limited casesno city lot minimum on file | — | No / unconfirmed | 2026-09-07 (not fully verified) |
| Mantua | Box Elder | allowed with conditionsno city lot minimum on file | allowed only in limited casesno city lot minimum on file | — | No / unconfirmed | 2026-09-07 (not fully verified) |
| Elwood | Box Elder | allowed with conditionsno city lot minimum on file | allowed only in limited casesno city lot minimum on file | — | No / unconfirmed | 2026-09-07 (not fully verified) |
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Unincorporated Box Elder County land follows county zoning, which this table does not cover. Planning information, not legal advice or a permit.