ADU or garage conversion: which one fits your property

Accessory dwelling units are the most common question we get now that almost nobody asked ten years ago. Homeowners want space for a parent, a grown child, or rental income, and they want to know what their lot will allow.

There are three routes, and they are not interchangeable.

Garage conversion

Converting an existing attached garage into living space. The walls, roof and foundation already exist, which makes this the least expensive of the three by a wide margin.

Works well when: the garage is already attached, you do not depend on it for parking or storage, and you want the shortest path to usable space.

The catch: a garage slab is usually not insulated and often sits lower than the house floor. There is no plumbing. The ceiling is frequently lower than a bedroom ceiling. All of that is solvable, and every one of those fixes is a line on the estimate. Together they close part of the gap with a purpose built unit.

Attached ADU

New square footage built onto the existing house, with its own entrance, kitchen and bathroom.

Works well when: you have side or rear yard to build into and you want the utility runs short. Sharing a wall with the house keeps plumbing and electrical simpler than running them across a yard.

The catch: it changes how the house reads from the street, and tying a new roof into an existing roof is detail work that separates careful builders from fast ones.

Detached ADU

A separate structure in the backyard. The most expensive of the three, and the most flexible.

Works well when: you want genuine separation, for a tenant or for family, and the lot has room for it.

The catch: everything has to be run to it. Water, sewer, electrical, sometimes gas. Trenching across a finished yard is real work and real money, and the distance from the house to the unit affects the budget more than the size of the unit does.

Confirm the rules before you plan anything

California has made ADUs substantially easier to build than they once were, and state law sets a floor that cities work within. Setbacks, height limits, parking, utility connection requirements and fees are handled locally, and they change.

Confirm the current rules for your specific parcel with City of Fontana Planning and Building and Safety before you commit to a design. We do this as part of planning a project, and we would tell you to do it even if you hired someone else. A design drawn against last year rules is wasted money.

We build all three

If you want to know which of the three your lot actually supports, call us and we will come look at it. The visit and the estimate are free.