Box Elder County · 20,319 residents
Brigham City ADU rules
Brigham City: internal ADUs allowed; detached ADUs allowed. Owner occupancy applies.
Internal ADU (inside the home)
Detached ADU (backyard building)
✓ Checked against city sources on September 24, 2026 See sources
Brigham City ADU rules at a glance
| Rule | Internal ADU (basement, attic, inside the home) | Detached ADU (backyard building) |
|---|---|---|
| Allowed? | Allowed | Allowed |
| Minimum lot | Not yet verified — confirm with the city | Brigham City's ADU code does not set a minimum lot size for a detached ADU; the unit must meet the zone's accessory-building standards. |
| Owner occupancy | The owner of the primary home must live on the property, in either the main home or the ADU. | The owner of the primary home must live on the property, in either the main home or the ADU. |
| Parking | One additional on-site hard-surfaced parking space (concrete, asphalt or pavers) reserved for the ADU. | One additional on-site hard-surfaced parking space (concrete, asphalt or pavers) reserved for the ADU. |
| Size limits | No minimum or maximum size for an ADU created inside the existing home. | Detached ADUs must be between 300 and 1,000 sq ft. |
| Height | Not yet verified — confirm with the city | Limited to 20 ft to the roof peak when located outside the main home's buildable area. |
| Setbacks | Not yet verified — confirm with the city | Detached ADUs must meet the zone's accessory-building standards and be within 150 ft of a fire apparatus access road. |
| Zones | Permitted use in the MU-40, MU-80, MU-160, A-1, A-5, RR-1, RR-5, R-1-10, R-1-8, R-1-6, R-M-7, R-M-15, R-M-30, GC and CBD zones; one ADU per detached single-family home. | Permitted use in the MU-40, MU-80, MU-160, A-1, A-5, RR-1, RR-5, R-1-10, R-1-8, R-1-6, R-M-7, R-M-15, R-M-30, GC and CBD zones; one ADU per detached single-family home. |
| Short-term rentals | An ADU may not be rented or occupied for less than 30 consecutive days. | An ADU may not be rented or occupied for less than 30 consecutive days. |
| Permit process | File a land use application with the city; no construction may begin until building permits are issued. A rental business license is required before renting, and a notice is recorded with the Box Elder County Recorder. | File a land use application with the city; no construction may begin until building permits are issued. A rental business license is required before renting, and a notice is recorded with the Box Elder County Recorder. |
Proposed or pending changes
Not adopted as of September 24, 2026. They do not change the rules above until the city adopts them.
- No Brigham City ADU ordinance amendment for S.B. 284 was found in 2026 records. The existing code already permits detached ADUs with no lot-size minimum, which is more permissive than the 11,000 sq ft statewide floor that takes effect Oct. 1, 2026.
State law: detached ADUs from October 1, 2026
Brigham City is a “specified municipality” under Utah S.B. 284. Beginning October 1, 2026, it must permit one detached ADU as a permitted use on a lot of 11,000 sq ft or more that has a detached single-family home. The city can still apply setbacks, height, design, owner-occupancy and limited parking rules, and it may allow detached ADUs on smaller lots. How the state ADU laws work.
How our property map screens Brigham City lots
The map colors parcels using the rules on this page and the recorded lot size. A color is a planning screen, not a permit; Brigham City makes the decision.
- No numeric external minimum is recorded for Brigham City. The map keeps the statewide 11,000 sq ft external screen and shows the researched status (generally allowed) on the property report.
- "Likely" above 15,000 sq ft is this site's planning band for a large recorded lot. It is not a sentence in the Brigham City code. Owner occupancy, parking, setbacks, zones, and HOA rules below still have to be checked.
Planned communities, PRDs and PUDs
Reviewed on September 22, 2026 against this city's research file, its published ADU page where one was found, and Utah meeting packets. No adopted sentence was confirmed that allows or bans an ADU in every PUD, PRD, PRUD, or planned community. If the assessor class or subdivision name says PUD, PRD, PRUD, planned unit development, planned residential development, planned community, resort community, or master planned community, the map keeps that lot highly unlikely regardless of size. A plat, CC&Rs, or development agreement can still prohibit an ADU where the zone allows one.
Sources
We link only to government sources and public meeting records. Codes change; confirm the current version with Brigham City before you apply.
- Brigham City — Accessory Dwelling Units
Official city ADU page (application instructions); its body is script-rendered and could not be text-verified by this review.
- Brigham City Planning Commission minutes, Apr. 7, 2026 — 2026 legislative update
City planner reviewed 2026 state housing/ADU bills; said the city 'remains well positioned' but will need administrative adjustments.
- Utah S.B. 284 (2026) enrolled — Utah Code 10-21-304
Statewide detached-ADU rules effective Oct. 1, 2026.
- U.S. Census Bureau Vintage 2024 Utah city population estimates
2024 population 20,319; Box Elder County 64,120.
- Utah Code 10-2-301 — classification of municipalities
10,000-29,999 = fourth class.
- Utah Code 17-50-501 — classification of counties (superseded 2021 text)
31,000-124,999 = third-class county; confirm against the current recodified section.
- Official Brigham City website
Common Brigham City ADU questions
Can you build an ADU in Brigham City?
Brigham City: internal ADUs allowed; detached ADUs allowed. Owner occupancy applies. This is planning guidance, not a permit. Confirm the zone on your parcel with Brigham City.
What lot size does Brigham City require for an ADU?
Internal ADU: Not yet verified — confirm with the city. Detached ADU: Brigham City's ADU code does not set a minimum lot size for a detached ADU; the unit must meet the zone's accessory-building standards.
Does Brigham City require the owner to live on the property?
Internal ADU: The owner of the primary home must live on the property, in either the main home or the ADU. Detached ADU: The owner of the primary home must live on the property, in either the main home or the ADU.
How much parking does a Brigham City ADU need?
Internal ADU: One additional on-site hard-surfaced parking space (concrete, asphalt or pavers) reserved for the ADU. Detached ADU: One additional on-site hard-surfaced parking space (concrete, asphalt or pavers) reserved for the ADU.
Can an ADU in Brigham City be a short-term rental?
Internal ADU: An ADU may not be rented or occupied for less than 30 consecutive days. Detached ADU: An ADU may not be rented or occupied for less than 30 consecutive days.
What does it cost to build an ADU in Brigham City?
Wasatch Front planning bands are often about $55,000–$145,000 for an internal suite, $70,000–$175,000 for a garage conversion, and $95,000–$250,000 or more for a new detached unit, before unusual site work. These are planning ranges, not bids.
Can an HOA block an ADU in Brigham City?
City approval does not override CC&Rs or plat notes. Read the HOA documents and your subdivision plat before you design. A private restriction can stop a unit the city would otherwise allow.
Before you design: general checks for any Utah ADU
General planning advice, not Brigham City code.
- Confirm the zoning district on the city zoning map. The county assessor’s “residential” class is not zoning.
- Read your HOA CC&Rs and subdivision plat notes; private restrictions can block a unit the city allows.
- Sketch existing and proposed parking. Driveway geometry and access often decide what fits.
- Ask early about sewer, water and electrical capacity; utilities can force a redesign.
- Expanding a building’s footprint usually triggers full setback and height rules.
Nearby city ADU rules
Want to know what fits on your Brigham City lot?
Free, no obligation. We review your parcel against these rules and, if you want, introduce independent design and construction partners. Partners may pay us for referrals.
Utah ADU Builder provides educational planning guidance. This page is not legal advice and not a permit. Population: U.S. Census Bureau population estimate (2024). Editorial standards.