ADU rules in Texas are set one council vote at a time
By July 2026, Austin had approved 1,309 new housing units under HOME Phase 1, a code amendment its council adopted in December 2023 that allows up to three units on most single-family lots. Builders who understood that vote early got first pick of the lots that suddenly penciled. The downside case is quieter: an ADU project designed for rules that no longer exist, or never existed in that city.
The same building can be legal, conditional, or prohibited
Dallas has allowed ADUs since June 2018, but not by right. There are two paths: a neighborhood-initiated ADU overlay, or an individual trip to the Board of Adjustment. Designing a casita for a Dallas lot assuming a by-right permit means designing for a path that does not exist. The ordinance also carries a penalty of up to $2,000 for violations.
San Antonio rewrote its ADU rules in a 191-amendment code update effective January 2023. It allowed separate utility lines, removed the one-bedroom cap, permitted closer construction to property lines, and added a two-story cap. It retained an off-street parking requirement for units over 800 square feet and an owner-occupancy rule, with ADUs subject to the city's short-term rental ordinance.
Houston moved its second-dwelling-unit ceiling from 900 to 1,500 square feet in September 2023. Austin followed HOME Phase 1 with Phase 2 in May 2024, creating a small-lot category down to 1,800 square feet. Four large Texas cities have different rule sets, each moved by public votes.
Late discovery has specific prices
Austin's transition rules show how timing binds. A three-unit project filed before February 5, 2024 needed a new building-permit application to use the HOME rules. An approved pre-HOME project could opt in through a major revision only before framing inspection. Filing on the wrong side of a transition rule can mean a new application, not a phone call.
San Antonio's 800-square-foot parking trigger works the same way. Discover it after the site plan is drawn and the site plan must change. A Dallas ADU rented in violation of an overlay or board condition can run against a $2,000 penalty ceiling.
These details sit in staff reports, code-amendment packets, and hearing agendas. They do not circulate on their own.
Five questions to answer before drawing the unit
First, is an ADU allowed by right, through an overlay, or only after discretionary approval? Second, does the rule require owner occupancy in the main house or accessory unit? Third, what size, height, lot coverage, setback, and entrance limits apply? Fourth, does the unit trigger parking, separate utility, fire-access, or design requirements? Fifth, may it be rented short term, long term, or only occupied by a defined household member?
Answer those questions from the current code and the adopted ordinance, then inspect pending agendas for changes. A staff memo may propose several options while a commission recommends only one. The council can amend the proposal at the meeting. Record the actual motion, effective date, and any transition rule rather than treating the initial draft as the final standard.
Builders and owners should also separate entitlement from construction compliance. Permission to place an ADU on a lot does not resolve building code, utility capacity, drainage, tree, historic district, deed restriction, or private HOA issues. Agenda monitoring is useful because it catches the municipal land-use rule while there is still time to revise a plan, but the project still needs a parcel-specific review before money is committed. Confirm every layer with the authority that administers it and retain the written guidance.
Where AgendaWire fits
AgendaWire polls monitored sources every 15 minutes and classifies agenda items against the ADU topic, including accessory dwelling, garage apartment, granny flat, casita, and secondary dwelling. Matches include a verbatim quote and the official source link.
Current coverage includes Dallas City Council, Fort Worth City Council, and the commissioners courts of Dallas, Ellis, Kaufman, Parker, and Wise Counties. Austin, San Antonio, and Houston illustrate the same one-vote dynamics; the current watch runs in DFW.
A watchlist is $40 per month for one topic and up to 20 custom keywords, with a 14-day free trial on the first. AgendaWire is source monitoring, not legal advice.
The difference between reading an ADU amendment when it posts and hearing about it at permit intake is measured in redesign fees and dead deals.