Which kind of ADU it is
Converting a garage or a basement starts with walls and a roof already in place. A new backyard cottage starts with a bare lot, and an above-garage unit starts with a structural review.
Ask which type the quote assumes and why.
Size and layout
A studio and a two-bedroom are different projects. Every added square foot adds framing, finishes and heating and cooling.
A compact, simple shape is usually cheaper to build than a complicated one.
The lot itself
Slopes, trees, tight access and the distance to the sewer line all change the work. A steep hillside lot needs a different foundation from a flat one.
Ask what the quote assumes about the lot, and what happens if the site surprises everyone.
Finishes and fixtures
Cabinets, flooring, windows and fixtures range from basic to custom. Two quotes may differ simply because they assume different finishes.
Compare the finish lists before you compare the totals.
Permits, utilities and schedule
City fees, utility connections and the time permits take all add to the total. A clear schedule with permit steps shows the quote was thought through.
Ask who pays the city fees and who handles the utility work.
