Utah County · 10,304 residents
Alpine ADU rules
Alpine: internal ADUs allowed; detached ADUs are not generally allowed today. Beginning October 1, 2026, state law (S.B. 284) requires the city to permit a detached ADU on qualifying single-family lots of 11,000 sq ft or more. Owner occupancy applies.
Internal ADU (inside the home)
Detached ADU (backyard building)
Not yet fully verified · last reviewed September 7, 2026 See sources
Alpine ADU rules at a glance
| Rule | Internal ADU (basement, attic, inside the home) | Detached ADU (backyard building) |
|---|---|---|
| Allowed? | Allowed | Not generally allowed |
| Minimum lot | Not yet verified — confirm with the city | 11,000 sq ft. Guest house: ≥5 acres; standard DADU: not allowed under ADU definition (internal-only). SB 284 may force DADU allowance on ≥11,000 sq ft lots from 2026-10-01 if Alpine is a specified municipality — local implementing ordinance status unknown |
| Owner occupancy | Required; temporary absence ≤3 years or care-facility placement with advance application | n/a |
| Parking | ≥4 off-street spaces total for lot; ≥1 designated for ADU (garage/driveway count) | n/a for prohibited DADU |
| Size limits | No explicit sq ft max in ADU section; must meet IRC/IBC | n/a |
| Height | Not yet verified — confirm with the city | n/a |
| Setbacks | Separate outside entrance required | Detached accessory structures require recorded agreement not to be used as dwelling/ADU |
| Zones | Permitted use in TR-10,000, CR-20,000, CR-40,000, CE-5 (ADU permit from Building Dept). Conditional use in CE-50 | n/a |
| Permit process | ADU permit + building permits; one meter per utility in owner's name | n/a until SB 284 local ordinance |
State law: detached ADUs from October 1, 2026
Alpine 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 Alpine 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; Alpine makes the decision.
- Because external ADUs are not typical in the Alpine research, the map does not mark a new external ADU as likely there.
- "Likely" above 15,000 sq ft is this site's planning band for a large recorded lot. It is not a sentence in the Alpine 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.
Planning notes for Alpine
Start with Alpine’s accessory-apartment application and a plan of the existing home. The city posted an August 18, 2026 hearing specifically about detached ADUs, so a backyard proposal deserves a fresh check of the final ordinance and effective date rather than relying on an older internal-only summary.
Bring these to your review
- Existing floor plan, separate entrance and proposed kitchen/bathroom
- Property zone, proposed footprint and utility connections
- Any detached-ADU ordinance number and effective date supplied during review
The question to resolve first
Can this design follow Alpine’s existing pathway, or should the application use the new detached-ADU standards?
Sources
We link only to government sources and public meeting records. Codes change; confirm the current version with Alpine before you apply.
- Alpine Building Department — accessory apartment application
Published city guidance
- Alpine Planning Commission — August 18, 2026 detached ADU hearing
Hearing notice; adoption not established by this source
- Utah S.B. 284 (2026), enrolled bill
Statewide detached-ADU requirements for specified municipalities, operative October 1, 2026.
- Official Alpine website
Common Alpine ADU questions
Can you build an ADU in Alpine?
Alpine: internal ADUs allowed; detached ADUs are not generally allowed today. Beginning October 1, 2026, state law (S.B. 284) requires the city to permit a detached ADU on qualifying single-family lots of 11,000 sq ft or more. Owner occupancy applies. This is planning guidance, not a permit. Confirm the zone on your parcel with Alpine.
What lot size does Alpine require for an ADU?
Internal ADU: Not yet verified — confirm with the city. Detached ADU: 11,000 sq ft minimum. Guest house: ≥5 acres; standard DADU: not allowed under ADU definition (internal-only). SB 284 may force DADU allowance on ≥11,000 sq ft lots from 2026-10-01 if Alpine is a specified municipality — local implementing ordinance status unknown.
Does Alpine require the owner to live on the property?
Internal ADU: Required; temporary absence ≤3 years or care-facility placement with advance application. Detached ADU: n/a.
How much parking does a Alpine ADU need?
Internal ADU: ≥4 off-street spaces total for lot; ≥1 designated for ADU (garage/driveway count). Detached ADU: n/a for prohibited DADU.
What does it cost to build an ADU in Alpine?
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 Alpine?
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 Alpine 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
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Utah ADU Builder provides educational planning guidance. This page is not legal advice and not a permit. Population: UGRC POPLASTESTIMATE / Census-derived municipal estimates (manual fill where UGRC blank). Editorial standards.