Tooele County · 14,417 residents
Grantsville ADU rules
Grantsville: internal ADUs allowed (lot 6,000+ sq ft); detached ADUs allowed (lot 12,000+ sq ft).
Internal ADU (inside the home)
Detached ADU (backyard building)
Not yet fully verified · last reviewed September 7, 2026 See sources
Grantsville ADU rules at a glance
| Rule | Internal ADU (basement, attic, inside the home) | Detached ADU (backyard building) |
|---|---|---|
| Allowed? | Allowed | Allowed |
| Minimum lot | 6,000 sq ft. Prohibited if lot <6,000 sq ft (Ch. 25). | 12,000 sq ft. Prohibited if lot <12,000 sq ft (Ch. 25). |
| Owner occupancy | Either primary or ADU occupied by owner of record (25.2.2). | Owner in primary or ADU. |
| Parking | 1 additional on-site stall per ADU; not in front/side street setbacks except approved driveway; replace garage stalls if displaced (25.2.7). | 1 additional on-site stall (25.2.7). |
| Zones | Permitted in R1-8, R1-12, R-1-21, RR-1, RR-2.5, RR-5, A-10, CN, CS, CD, PUD, MU; also RM-7/RM-15 only on single-family lots; not in mobile homes (25.2.3). | Same SFR list as ADUs generally; subject to DADU lot-size rule. |
| Permit process | Application process in Ch. 25; business license required; unique address; IADUs exempt from impact fees. | Building permit; DADUs subject to impact fees; unique address; business license. |
State law: detached ADUs from October 1, 2026
Grantsville 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 Grantsville 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; Grantsville makes the decision.
- The statewide map screen starts a new external ADU at about 11,000 sq ft. Grantsville's researched external minimum is 12,000 sq ft. Lots below that city minimum stay highly unlikely on the map even when they clear 11,000 sq ft.
- "Likely" above 15,000 sq ft is this site's planning band for a large recorded lot. It is not a sentence in the Grantsville code. Owner occupancy, parking, setbacks, zones, and HOA rules below still have to be checked.
Planned communities, PRDs and PUDs
The Grantsville research file records Chapter 25, section 25.2.3, listing the PUD zone among the zones where an ADU is permitted. A PUD label in Grantsville uses the lot-size screen instead of an automatic ban. A plat or CC&Rs can still prohibit the unit. This sentence was not re-read from a new code PDF on September 22, 2026.
Planning notes for Grantsville
Grantsville has considered changes to its Chapter 25 ADU standards. Older detached-unit summaries may therefore miss a useful option. We can help compare a basement conversion with a backyard design against the final code, including parking, owner occupancy and building separation.
Bring these to your review
- Proposed internal or detached layout
- Existing parking and distance between buildings
- Any prior ADU approvals or recorded restrictions
The question to resolve first
Which version of Chapter 25 governs this application, and does it provide a detached pathway for this lot?
Sources
We link only to government sources and public meeting records. Codes change; confirm the current version with Grantsville before you apply.
- Utah S.B. 284 (2026), enrolled bill
Statewide detached-ADU requirements for specified municipalities, operative October 1, 2026.
- Official Grantsville website
Common Grantsville ADU questions
Can you build an ADU in Grantsville?
Grantsville: internal ADUs allowed (lot 6,000+ sq ft); detached ADUs allowed (lot 12,000+ sq ft). This is planning guidance, not a permit. Confirm the zone on your parcel with Grantsville.
What lot size does Grantsville require for an ADU?
Internal ADU: 6,000 sq ft minimum. Prohibited if lot <6,000 sq ft (Ch. 25). Detached ADU: 12,000 sq ft minimum. Prohibited if lot <12,000 sq ft (Ch. 25).
Does Grantsville require the owner to live on the property?
Internal ADU: Either primary or ADU occupied by owner of record (25.2.2). Detached ADU: Owner in primary or ADU.
How much parking does a Grantsville ADU need?
Internal ADU: 1 additional on-site stall per ADU; not in front/side street setbacks except approved driveway; replace garage stalls if displaced (25.2.7). Detached ADU: 1 additional on-site stall (25.2.7).
What does it cost to build an ADU in Grantsville?
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 Grantsville?
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 Grantsville 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 Grantsville 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: UGRC POPLASTESTIMATE / Census-derived municipal estimates (manual fill where UGRC blank). Editorial standards.