Detached ADU Builder in Lehi, Utah
Utah's SB 284 reset the lot-size math for detached ADUs in Lehi. The state's ADU provisions take effect October 1, 2026, and the qualifying floor drops from roughly a third of an acre to about a quarter acre. Lehi lots that were too small under the old rule may now be potentially eligible.
Stoneward Construction is a feasibility-first DADU builder based right here in Lehi. Before anyone talks about building, we tell you honestly whether your property is likely to qualify and physically works.
What Changed for Lehi Homeowners
The single biggest change is lot size. Under Lehi's prior detached-ADU standards, a qualifying lot needed roughly 14,520 square feet — about one-third of an acre. SB 284 lowers the floor that qualifying cities must honor to 11,000 square feet, closer to a quarter acre. That single change pulls a whole band of Lehi properties into the conversation for the first time.
The clearest new market is the 11,000 to 14,519 sq ft band — lots that sat just under Lehi's old third-of-an-acre line. If your Lehi lot falls in that range (or larger), sits in a single-family zone, and has a lawfully existing home, it's worth a fresh look. Just know that clearing the size floor makes a property potentially eligible — it doesn't waive the rest of Lehi's code.
Lehi's Detached ADU Rules That Still Apply
SB 284 opens the door on lot size. These are the local standards that still decide whether a detached ADU actually fits on your specific Lehi lot — the details we check before recommending you spend a dollar on design.
Placement & separation
The detached ADU sits beside or behind the primary home, with a minimum separation of about 6 feet between the two structures.
Setbacks from property lines
For a one-story unit up to 20 ft tall: about 5 ft where a wall has no standard windows, and about 10 ft where it does. Two-story units or anything taller than 20 ft must meet the primary dwelling's setbacks.
Height limit
Maximum height around 35 ft — and in no case taller than the primary home on the lot.
Off-street parking
Generally one stall for units under 650 sq ft and up to two stalls for larger units, each roughly 9 by 20 ft. Your driveway and lot have to physically fit it.
Minimum living area
A detached ADU must provide at least about 300 sq ft of living space to be a permitted dwelling.
Utilities & access route
Utilities generally run through the primary dwelling, and Lehi requires a 12-ft all-weather emergency and utility access route to the unit.
Permanent foundation
The ADU must be built on a permanent foundation — not a movable or temporary structure.
Slope & grading
Slopes over 20% are restricted, and lots with 10–20% slope typically require a grading plan as part of approval.
Standards summarized from Lehi's detached ADU requirements and shared for general guidance. Exact figures, easements, HOA or development-agreement terms, and lot-specific conditions are verified for your address during feasibility.
Where Lehi's Rule Change Stands
Lehi City advanced its SB 284-compliant detached ADU amendments to the City Council for final consideration on July 14, 2026, through Ordinance #2026-31. The statewide ADU provisions of SB 284 take effect October 1, 2026.
Because the local rules are being finalized right now, this is a genuinely time-sensitive window. We track Lehi's adoption closely and screen every property against both the state floor and the city's current standards — so the answer you get reflects where the code actually is, not where it was.
What This Looks Like on a Real Lehi Lot
A recent example is the Allred detached ADU at 409 West 900 North, in one of Lehi's older neighborhoods. It sits on a lot over half an acre, with the unit set about 12 feet from the side property line and off-street parking provided — a clean illustration of how setbacks, separation, and parking come together on an established property.
Older parts of Lehi also tend to need property-line cleanup — resolving fence lines, easements, and survey questions that don't match the record. It's the kind of thing that rarely shows up until you actually screen the parcel, and exactly why we start with feasibility instead of a design deposit.
What We Check for Your Lehi Lot
Meeting the SB 284 size threshold gets you in the door — it doesn't waive the rest of the code. Here's what our feasibility screen looks at before we ever recommend spending on design:
- Lot size and confirmation you clear the 11,000 sq ft floor
- Zoning — that your lot sits in a single-family dwelling (SFD) zone
- A lawfully existing single-family home on the property
- Setbacks, the 6 ft separation, and height limits against your layout
- Usable buildable area after setbacks and slope are applied
- Utility access — water, sewer, electrical, and the 12 ft access route
- Off-street parking Lehi still requires by unit size
- Easements, HOA, or development-agreement restrictions on your parcel
Want the full breakdown of our process from screen to occupancy? See our detached ADU services page, or read the full SB 284 breakdown.
A Local Lehi Builder Who Knows the Code
We're based in Lehi and work throughout Utah County. That means we know the local planning and building departments, the setback and parking standards that actually get projects approved, and how SB 284 layers on top of Lehi's existing rules.
We tracked SB 284 from the start, so we can tell you where your Lehi property stands under both the new statewide floor and the local standards that still apply.
Stoneward Construction LLC
262 S 2115 W, Lehi, UT 84043
Phone: (801) 888-0136
Email: [email protected]
Serving Lehi, American Fork, Pleasant Grove, Highland, Alpine, Saratoga Springs, Eagle Mountain & Utah County
Lehi ADU Questions
What was Lehi's old minimum lot size for a detached ADU?
Before SB 284, Lehi's standards effectively required about 14,520 sq ft — roughly a third of an acre. SB 284 lowers the floor to 11,000 sq ft, opening a band of Lehi lots between about 11,000 and 14,519 sq ft that were previously locked out on size alone.
Does hitting 11,000 sq ft guarantee I can build?
No. Meeting the size floor makes a lot potentially eligible, not automatically approved. Lehi still applies setbacks, a 6 ft separation from the primary home, parking, height limits, minimum living area, an access route, foundation, and slope rules. Easements, HOA or development-agreement terms, and the lot layout can still stop an otherwise qualifying property.
How far does the ADU sit from my house in Lehi?
Lehi requires roughly a 6 ft separation between the detached ADU and the primary home, with the ADU beside or behind the main house. Side and rear setbacks depend on wall design and height — generally 5 ft where a wall has no standard windows and about 10 ft where it does, with taller or two-story units held to the primary dwelling's setbacks.
How much parking does Lehi require?
Parking scales with unit size — generally one off-street stall under 650 sq ft and up to two for larger units, each around 9 by 20 ft. We confirm the exact requirement and whether your lot can fit it during the screen.
Is Lehi's SB 284 ordinance final yet?
Lehi City advanced its SB 284-compliant detached ADU amendments to the City Council for final consideration on July 14, 2026, through Ordinance #2026-31. The statewide ADU provisions take effect October 1, 2026. We track the local adoption and screen against both.
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