What Is an ADU?
An accessory dwelling unit (ADU) is a second, smaller home on a lot that already has a main house. In Texas you will hear them called backyard homes, granny flats, mother-in-law suites, guest homes, casitas, pool houses and garage apartments. Whatever the name, an ADU is a permanent structure with its own living space — usually a kitchen or kitchenette, a bathroom and a place to sleep — built to the International Residential Code (IRC) and the zoning code of the city where it sits.
Cowboy Tiny Homes works as both designer and builder on ADU projects, which means the same team that checks your setbacks also draws the plans and manages construction. Fewer handoffs means fewer surprises.
Types of ADUs We Build
| ADU type | What it is | Good fit when… |
|---|---|---|
| Detached backyard casita | A standalone small home in the back yard | You want privacy for guests, family or a tenant |
| Garage apartment | Living space above or in place of a garage | Your yard is small and you need to build up |
| Attached ADU / in-law suite | A separate unit sharing a wall with the main house | An aging parent needs to be close but independent |
| Pool house or guest house | A smaller unit with bath and lounge, sometimes a kitchenette | You entertain often or want a home office |
| Accessory structure | Studio, workshop or office without full living quarters | You need space, not a second dwelling |
Why Texas Homeowners Are Building ADUs
- Multigenerational living. Keep parents or adult kids close while everyone keeps their own front door.
- Rental income. A long-term tenant or, where allowed, a short-term rental can help cover your mortgage. Run your numbers with the ADU rental income calculator.
- Home office or studio. A real commute across the yard beats working from the kitchen table.
- Property value. A well-built, permitted second unit can add to what your property is worth and how it is used.
- Downsizing in place. Some owners move into the ADU and rent or hand over the main house.
ADU Rules in Texas: What to Check First
Texas has no single statewide ADU law for homeowners — rules come from your city, and outside city limits from your county, utility providers and any deed restrictions. Before design starts, our feasibility study looks at:
- Whether ADUs are allowed in your zoning district, and whether by right or only through a special exception or permit.
- Size limits, often expressed as a maximum square footage or a percentage of the main house.
- Setbacks, height and lot coverage, which decide where the ADU can go and whether a second story is possible.
- Parking, utilities and addressing, including whether the ADU can share the main home’s water, sewer and electric meters.
- Occupancy and rental rules, such as owner-occupancy requirements or short-term rental permits.
- HOA deed restrictions, which can prohibit or limit second dwellings even when the city allows them.
Rules differ a lot between cities. Austin’s HOME code changes allow more units on many residential lots, San Antonio permits ADUs in many residential districts with size and design standards, Houston has no traditional zoning but deed restrictions matter, and parts of Dallas have historically required a special exception. Local details are on our Austin, San Antonio, Houston, Dallas and Fort Worth pages, and the bigger picture is in our Texas tiny house laws guide. Always confirm current rules with your city, because ADU codes are changing quickly.
How Much Does an ADU Cost in Texas?
For planning purposes, builder-built detached ADUs in Texas typically run about $190 to $340 per finished square foot at standard finishes. That works out to roughly:
| ADU size | Typical range (standard finishes) |
|---|---|
| 400 sq ft studio casita | About $76,000 – $136,000 |
| 600 sq ft one-bedroom | About $114,000 – $204,000 |
| 800 sq ft two-bedroom | About $152,000 – $272,000 |
Utility runs from the main house, sewer tie-ins, tree removal, slopes and city fees can move these numbers. Basic finishes can trim costs about 15%; premium finishes can add 30% or more. Get your own estimate with the tiny home cost calculator and compare it with other options in our ADU vs park model vs tiny house on wheels guide.
Designing an ADU That Works for Everyone on the Lot
A backyard home changes how the whole property works, so we design the ADU and its surroundings together. Privacy comes first: window placement, entry location and landscaping keep the main house and the casita from looking straight into each other. Then come the practical details — a separate path from the street or driveway, a spot for trash bins, outdoor lighting and a small private patio for the ADU occupant.
If the ADU is for an aging parent, we plan for aging in place from the start: a zero-step entry, a curbless shower, wider doorways and blocking in the walls for future grab bars. If it is a rental, we focus on durable finishes, efficient heating and cooling, and a layout that rents well. If it is a studio or office, we prioritize natural light, sound separation and plenty of outlets.
Our ADU Design-Build Process
- Site visit and feasibility. We confirm what your lot allows and where the ADU can go.
- Design. Floor plans, elevations, roof, site and electrical plans, plus interior, exterior and 3D renderings that match your main house.
- Permits. Permit-ready drawings submitted to your city, with revisions handled if plan reviewers comment.
- Construction. Foundation, framing, utilities and finishes, with inspections at each stage.
- Move-in. Final inspection and a walkthrough of your new space.
Read more on how Cowboy Tiny Homes works, or browse house designs for layout ideas.