Houston ADU costs at a glance
| Type | Typical size | Typical Houston range |
|---|---|---|
| Detached garage to ADU | 350–500 sq ft | $60,000–$110,000 |
| New backyard cottage | 400–600 sq ft | $140,000–$220,000 |
| Garage apartment or larger ADU | 700–1,500 sq ft | $225–$325 per sq ft |
What drives the price
- Utilities: the distance to the sewer, water and electric service often costs more than the finishes.
- Foundation: floodplain elevation or a second story above a garage needs more engineering.
- Kitchen and bath: a full kitchen costs far more than a kitchenette.
- Separate meter: a second electric meter needs its own address and service.
- Matching the house: brick, roofline and windows that match look better and cost more.
Rules that decide if you can build
- Deed restrictions come first. If they prohibit a second dwelling, the city can’t override them.
- Inside the City of Houston, a second unit can be up to 1,500 square feet; up to 1,000 square feet needs no extra parking.
- Floodplain lots must build the floor at the required elevation.
- Short-term rentals must be registered with the city each year.
Common questions
Is a garage conversion the cheapest ADU?
Usually, when the slab and walls are sound and utilities are close. It reuses the structure, so most of the budget goes to insulation, plumbing, HVAC and finishes.
Does an ADU add value in Houston?
Often, through rental income or multigenerational use, but Houston resale data is limited. Plan it for how you’ll use it, not only for resale.
How long does an ADU take to build?
Plan 2–3 months for design and permits, then about 2–3 months for a garage conversion or 4–6 months for a new detached unit.
Sources
This guide is general information, not legal, tax or financial advice. Rules change; confirm details with the agency named in the sources or a licensed professional.
