Attached ADUs in Bountiful, UT

An attached ADU is an addition to the existing house that functions as its own dwelling. It shares at least one wall or a continuous roofline with the main home, but it has a separate entrance, its own kitchen and bathroom, and no internal doorway that has to stay open for it to work.

It suits properties where a detached unit does not fit — a lot without enough clear backyard, or one where getting equipment to the rear is genuinely impractical — but where converting a garage or basement is not the right answer either. Building outward from the house solves both problems at once.

Structurally it is the most demanding of the ADU types, because you are tying new construction into an existing building. The new foundation has to meet the old one properly. The roofline has to work rather than look bolted on. Where the two structures meet needs proper separation for sound and weather.

Done well, an attached unit reads as though the house was always that shape. Done carelessly, it reads as an addition — which is why exterior design matters more here than on any other ADU type.

For properties where both options are technically possible, attaching has some concrete advantages:

• Shorter utility runs — you are connecting to water, sewer and electrical service right where they already are, rather than trenching across the yard
• Less yard consumed — the footprint extends the house rather than occupying open backyard
• Simpler site access — work happens at the edge of the house, not at the back of a lot behind a narrow side yard
• Shared building envelope — one wall is already there, which affects both cost and heat loss through a Wasatch Front winter
• Practical for close family — near enough to check in easily, separate enough that both households have their own front door

The trade-off is privacy. A shared wall means some shared sound no matter how well it is detailed, and the two entrances are close together. For a long-term tenant that can matter; for a parent or an adult child it usually does not.

An attached build touches the existing house, so a few questions are worth answering early:

• Which side of the house — setbacks, the driveway, existing windows and where the sun falls all narrow this down quickly
• Where the second entrance goes — two front doors close together can look awkward; the answer is usually a side or rear entrance with its own path
• Sound separation — the shared wall assembly matters more than people expect, particularly if a bedroom backs onto it
• What happens to existing windows — the addition may cover openings in the current house, which affects light in rooms you already use
• Roofline complexity — a clean junction between old and new roof is a design problem worth solving on paper, and a cost driver
• Local rules — attached units are governed by city ordinance rather than Utah’s statewide internal-ADU protection, so confirm the position with Bountiful City

If the assessment points away from attaching, the alternatives are usually a detached ADU where the yard allows or a garage conversion where it does not. Every route starts with design work and continues into construction. We build attached units throughout Bountiful and South Davis County.