ADU Guide · 2026
A new building on a Utah lot.
A practical guide to accessory dwelling units in Davis and Weber counties — what the code allows, and the questions worth answering before anyone draws.
Types
What the code allows
01
Detached — new construction
A separate new building in the rear or side yard. Size, height, parking, and design standards are set by the city — and, as of 2026, by statewide rules on larger lots. This is the ADU type Kohottaa designs.
02
Internal / basement
A dwelling inside the existing house — usually a basement or a lockable wing. Legal in many zones under Utah’s 2021 law.
03
Attached / addition
A new wing that shares a wall or roof with the main house. Reviewed under local addition and ADU rules.
04
Garage conversion
The volume you already have, made habitable. Often the fastest path to a legal unit.
State law
The legislature opened the door. The city still holds the key.
Internal ADUs · 2021
House Bill 82 made internal accessory dwellings a permitted use in most residential zones. A basement or in-house unit that meets building code is no longer a political favor. Owner occupancy, parking, and short-term rental rules still belong to the city.
Detached ADUs · 2026
Senate Bill 284 has been in effect since October 1, 2026. It requires many Utah cities to allow a detached ADU as a permitted use on lots of 11,000 square feet or larger that already have a single-family house. Setbacks, height, size, and coverage remain local. Parking is capped at one stall under 650 square feet, or two stalls at 650 square feet and above.
The state sets a floor, not a floor plan. A Bountiful lot and an unincorporated Weber lot are different projects. We read the ordinance that applies to your parcel before schematic design.
Why an architect
The ordinance is not a floor plan.
Every city writes different rules for lot coverage, height, parking, and setbacks. An architect is how those rules become a building that fits the household, sits well next to the house you have, and arrives at the counter as a set they can stamp.
Before you write
A short readiness list
0 of 6 ready. None of these are required to inquire — they just make the first conversation useful.
Questions
Asked before the first visit
- Do you design basement, garage, or attached ADUs?
- Kohottaa’s ADU work is new detached construction — a separate building on the lot. If another path is a better fit for your property, we will say so early.
- Do I need an architect for a detached ADU?
- In unincorporated Weber County, a licensed architect is required when the detached unit does not match the main house — the ordinance names barn, agricultural, or local-historic styles. Elsewhere the law is often silent, but an architect is how you get a new building that is worth the permit.
- Can I rent the ADU?
- Usually yes, for long-term occupancy (30 days or more), if you meet owner-occupancy rules. Short-term rental is restricted or banned in many Davis and Weber cities. We do not design for a use the city will not allow.
- How large can it be?
- It depends on the city and the lot. Unincorporated Weber County allows a detached footprint from 400 to 1,500 square feet. Ogden is tighter. We start with your parcel, not a productized floor plan.
- Do you work on more than houses?
- Yes. Accessory dwellings are the focus. Other architectural work in Utah is within the practice — inquire if you have something in mind.
- What does a typical project cost to design?
- Feasibility and a schematic study are a modest first engagement. A full permit set for a custom ADU is a larger one. We quote in writing after we have seen the site — not from a website form.
This guide is educational, not legal advice or a substitute for your city’s current ordinance, building official, or recorded covenants. Kohottaa will verify the rules that apply to your parcel as part of feasibility.