Davis County · 25,660 residents
Farmington ADU rules
Farmington: internal ADUs allowed (lot 6,000+ sq ft); detached ADUs allowed (lot 10,000+ sq ft).
Internal ADU (inside the home)
Detached ADU (backyard building)
Not yet fully verified · last reviewed September 7, 2026 See sources
Farmington 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. Statewide statute includes a small-lot pathway around 6,000 sq ft for many internal ADUs — confirm how Farmington applies it on your zone. | 10,000 sq ft. Local minimum often cited at 10,000 sq ft — Already allows DADUs on ≥10,000 sq ft (more permissive than 11,000). Confirm permitted-use status and parking caps for SB 284. |
| Owner occupancy | Owner occupancy of primary or ADU; temp absentee ownership allowed for military/employment/family/quasi-public service | SSF: separate ownership/utilities; 2-year owner-occupancy after separation; additional lot-size rules if IADU retained |
| Size limits | IADU prohibited if lot <6,000 sq ft | DADU prohibited if lot <10,000 sq ft |
| Height | Not yet verified — confirm with the city | DADU footprint ≤ primary footprint; height subordinate to main building; accessory building standards of zone |
| Zones | Not yet verified — confirm with the city | DADU footprint ≤ primary footprint; height subordinate to main building; accessory building standards of zone |
| Permit process | ADU application + building permit | DADU footprint ≤ primary footprint; height subordinate to main building; accessory building standards of zone |
State law: detached ADUs from October 1, 2026
Farmington 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 Farmington 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; Farmington makes the decision.
- The statewide map screen starts a new external ADU at about 11,000 sq ft. Farmington's researched external minimum is 10,000 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 Farmington 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 Farmington
Farmington publishes an ADU/internal-ADU application, an internal-unit eligibility checklist and a toolkit covering ADUs and subordinate single-family dwellings. These labels describe different planning routes. Have your proposed backyard or internal design classified before assuming one application or set of setbacks covers every option.
Bring these to your review
- Internal-ADU eligibility checklist where applicable
- Concept footprint and relationship to the main home
- Parcel zone, overlay and ownership information
The question to resolve first
Is this proposal an internal ADU, detached ADU or subordinate single-family dwelling under current Farmington rules?
Sources
We link only to government sources and public meeting records. Codes change; confirm the current version with Farmington before you apply.
- Farmington Applications & Forms — ADU and SSF toolkit
Published city application directory
- Utah S.B. 284 (2026), enrolled bill
Statewide detached-ADU requirements for specified municipalities, operative October 1, 2026.
- Official Farmington website
Common Farmington ADU questions
Can you build an ADU in Farmington?
Farmington: internal ADUs allowed (lot 6,000+ sq ft); detached ADUs allowed (lot 10,000+ sq ft). This is planning guidance, not a permit. Confirm the zone on your parcel with Farmington.
What lot size does Farmington require for an ADU?
Internal ADU: 6,000 sq ft minimum. Statewide statute includes a small-lot pathway around 6,000 sq ft for many internal ADUs — confirm how Farmington applies it on your zone. Detached ADU: 10,000 sq ft minimum. Local minimum often cited at 10,000 sq ft — Already allows DADUs on ≥10,000 sq ft (more permissive than 11,000). Confirm permitted-use status and parking caps for SB 284.
Does Farmington require the owner to live on the property?
Internal ADU: Owner occupancy of primary or ADU; temp absentee ownership allowed for military/employment/family/quasi-public service. Detached ADU: SSF: separate ownership/utilities; 2-year owner-occupancy after separation; additional lot-size rules if IADU retained.
What does it cost to build an ADU in Farmington?
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 Farmington?
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 Farmington 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 Farmington lot?
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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.