Why a conversion, and not a new build?
If you’ve already got a detached garage on your Austin lot — the kind that quietly stores bikes and yard tools — converting it is often the fastest, lowest-cost way to add an accessory dwelling unit (ADU). You skip the foundation pour. You skip the framing of the shell. You skip the slow site work that adds weeks to a new-construction schedule. What’s left is the part that makes a garage feel like a home: insulation, finishes, plumbing, electrical, windows, and a code-compliant entry. That’s a substantially smaller scope than starting from scratch.
When a garage works (and when it doesn’t)
Not every garage converts cleanly. Three things decide the answer during our first visit: the slab, the headroom, and the electrical service. A slab in good shape can usually be insulated, flashed, and built on top of without being torn out — but a cracked or sloping slab adds real cost. Austin’s residential code counts a floor as “enclosed space” only when there’s more than six feet of clear height (LDC § 25-2-773(E)(1)(b)), so very low garages can run into ceiling-height issues that need to be addressed in design. Electrical service capacity is the third variable — many older garages have a 60- or 100-amp panel that won’t carry a full ADU load, so the budget needs to include a service upgrade and a new sub-panel.
Beyond the structure itself, Austin’s HOME Phase 1 rules (adopted late 2023) allow up to three dwelling units on a single-family lot zoned SF-1, SF-2, or SF-3 if the lot is at least 5,750 sq ft. So in most parts of Austin, a converted garage can be a fully permitted second or third unit — not a workaround, not a “rec room,” but a real ADU with its own address, utility metering, and right to be rented. The same impervious cover and building coverage caps apply (45% and 40% respectively for two- or three-unit residential), but a converted garage rarely adds new impervious surface, which can actually make the math easier than a new structure.
What the process looks like
We start with a site visit (no design fee for the visit itself) to look at the slab, headroom, electrical, and where water and sewer can reach. If conversion makes sense, we move into a design phase: framing details for insulation and finishes, where the kitchen and bath go, window and door placements, and any code upgrades the City of Austin plan reviewer will flag. From there we pull the residential building permit through Austin’s AB+C portal and handle the back-and-forth on plan review. Once the permit is active, framing and MEP start; finishes and a final inspection close it out.
Timeline and cost — honest ranges
A garage conversion typically runs faster than new construction because there’s no foundation pour, no exterior shell, and (often) no new utility tap. Permit timelines vary with the City of Austin’s queue, but conversion permits tend to come back faster than new-construction permits because the plan scope is smaller. As for cost: we don’t publish a single number because the slab condition, electrical service, and finish level swing the budget materially. The honest answer is “conversions almost always cost less than building new at the same square footage, but how much less depends on what we find on the site visit.” If you want a real number for your lot, the fastest path is a quick call or an in-person visit — we’ll walk through the variables that apply to your specific garage and Travis County address.
