Garage Conversion vs. Detached ADU: Which Should You Build?
By Eric Dexter, Owner & Builder ·
Two of the most popular ways to add a home to your property are converting your garage into a living space (an attached ADU) or building a detached ADU (DADU) in the backyard. Both add legal, independent living space — but they suit different lots, budgets and goals. Here's how to choose.
Garage conversion (an attached ADU)
A garage conversion reuses a structure you already have, so it can be the lower-cost path — if the garage is a good candidate. The catch: you're working within the existing footprint, ceiling height and foundation, and you still have to add everything that makes it a real home — insulation, egress windows, plumbing, heating and finishes. Those upgrades can quietly close the gap with a new build.
Detached ADU (DADU)
A DADU is a new, standalone structure. It costs more because it needs its own foundation, utilities and roof — but you get a purpose-built home with real privacy, a layout designed from scratch, and stronger rental appeal. For many owners that's worth the premium.
Cost
A clean garage conversion can come in below a detached build, but a conversion that needs new foundation work, drainage or major systems can cost as much as a small DADU. A DADU is a full new-build budget — in the Seattle area, most run $375,000–$600,000+ all-in. Price your options with the ADU cost calculator and see the full breakdown on our realistic costs page.
Privacy & rental value
A detached DADU rents better and lives better — separate entrance, no shared walls, its own outdoor space. A garage conversion attached to (or under) the main house is a bit less private, which can matter for tenants. If rental income is the goal, see renting out your ADU.
Which should you build?
If you have a solid, suitable garage and want the most affordable path, a conversion is worth pricing. If you want maximum privacy, rental value and a layout built for how you'll actually use it — or you don't have a convertible garage — a DADU is usually the better long-term move. Not sure which your lot favors? Talk to us and we'll walk both options for your property.
