Maybe you want to turn the garage into a one-bedroom apartment. Maybe you want a detached cottage behind the house, or a suite for a parent with its own entrance and its own porch.
If you’ve ever stood in your backyard and thought “we could build something out here,” this is for you.
What an ADU Actually Is
ADU stands for accessory dwelling unit. It’s a zoning term for a smaller, second living space that shares a lot with a primary house. Think: garage apartment, backyard cottage, in-law suite with its own entrance, converted detached structure.
It is a place people live, permitted and built to the city’s building code for one. Not a guest room. Not an unpermitted Airbnb cabin. Not a glorified shed with a bed in it.
People build ADUs for three big reasons, often some mix of all three:
Rental income: a long-term tenant or a furnished rental, where the zoning on your lot allows one (more on that below).
Multi-generational living: aging parents, adult children figuring out life, a sibling in transition, a family member who needs proximity without sharing the same kitchen.
Flexible workspace: a real home office, a studio, a creative space, somewhere to actually focus that isn’t fifteen feet from the kitchen.
All three answer questions a lot of families are quietly asking. Where do my parents live when they’re older? How do I help my adult kid without housing them inside my house? Where do I work? Could my backyard earn something?
What Fort Worth Currently Allows
Fort Worth’s zoning ordinance treats an ADU as a habitable accessory building and sets most of its rules in two sections, §5.300 and §5.301. As of October 2026, here’s what shapes a backyard ADU:
- It can’t have more square footage than the house (§5.300(c)).
- It can’t be taller than the house (§5.301(c)(2)).
- It keeps the house’s side and rear setbacks, and every roof on the lot, house and ADU together, has to fit inside your district’s maximum lot coverage (§5.301(a)(2) and (a)(3)).
- It has to meet the city’s building code for a place people live (§5.301(c)(1)).
- Its water, electric and gas come through the meters that serve the house (§5.300(b)).
- And in a one-family district, it “may be used only as an accessory dwelling unit and may not be used as a separate independent residence” (§5.301(c)(3)). If renting it out is the plan, find out what that line means for your lot before you design around a tenant.
Some parts of the city write their own rules. In the Berry/University form-based district, for one, a second unit can’t be more than 33% of the main house or 1,000 square feet, whichever is less. And ordinances change, so the current rules for your lot need checking before anyone draws plans. That’s the first thing we do: we read your lot and tell you plainly whether it works before you spend anything on design.
What Changed at the State Level in 2025
Two 2025 Texas laws, SB 15 and HB 24, changed how big Texas cities handle new housing. Both took effect September 1, 2025, and neither one changes what you can build behind the house you already own.
SB 15 is about new subdivisions. In a city of more than 150,000 people in a county of more than 300,000, which includes Fort Worth, the city can’t require lots bigger than 3,000 square feet on an unplatted tract of five acres or more zoned for single-family homes. It decides how small the lots in a new neighborhood can be, not what goes in an existing backyard.
HB 24 is about rezoning. When a rezoning would allow more housing, a neighbor protest only counts if the owners of at least 60 percent of the land within 200 feet of it sign it, and a protest that counts means the city council needs a majority of all its members to pass the change. An ADU on a lot that already allows one doesn’t need a rezoning.
A 2025 bill written for ADUs, SB 673, would have set statewide rules for them. It passed the Senate and died in the House, so it isn’t law. Fort Worth’s own rules, above, still decide your lot.
