Triplexes and fourplexes could be built under the house code, with sprinklers and fire walls. The council sets a hearing Nov. 19

Building a triplex or fourplex in Austin today means following the same commercial building code used for apartment complexes. City staff have now drafted a way around that. On Nov. 19 the City Council is scheduled to set a public hearing on a local amendment that would let small three- and four-unit buildings be permitted under the International Residential Code, the code for houses and duplexes. The buildings would have to meet added fire and life-safety rules.

The change would not affect zoning, meaning how many homes are allowed on a lot. It covers how those buildings are designed and inspected.

What staff propose

The staff summary describes a new "Appendix BP" to the residential code. It would apply to one building with three or four attached units that are not townhouses, with no more than 6,000 square feet of floor area. Those buildings could be built under the rules for two-family homes, plus these requirements:

• Sprinklers. Automatic sprinkler systems designed under IRC Section P2904 or NFPA 13D, with extra coverage for some garages, carports, shared exits and covered wood exterior areas.
• Fire separation. Fire-rated walls and floors between units and shared exit spaces, without the reduction usually allowed when a building has sprinklers.
• Shared stairs and halls. These must lead directly outside and be enclosed by one-hour fire-rated construction. Doors into them need a 45-minute rating, smoke gaskets and self-closing, self-latching hardware.
• No shared air paths. No ducts or air openings between units and shared exits, and no wall cavities used as air plenums.
• Height limits. No more than two units stacked vertically, no habitable attics above the third story, and no rooftop decks shared by more than one unit.
• Alarms and access. Smoke alarms in each unit must connect to a notification device in the shared exit space if one exists. Owners must sign an access agreement so a contractor or code official can inspect fire and life-safety systems in units occupied by others.

Fire-flow requirements, the water supply available for firefighting, would be calculated as for a duplex.

What our records add

The council asked for this in July. On July 23, the council voted 9-1 for Council Member Krista Laine's resolution starting the amendment. Council Member Marc Duchen voted no, and Council Member Vanessa Fuentes was absent. Co-sponsors were Council Members Zohaib "Zo" Qadri and Ryan Alter, Mayor Kirk Watson and Mayor Pro Tem José "Chito" Vela.

At that meeting, Laine said any building with three or more units is now treated as an apartment building, so a fourplex on a small lot is reviewed like "a downtown high rise." She described a four-unit home for families experiencing homelessness in her district's extraterritorial jurisdiction. She said its renovation costs nearly doubled under the commercial code. She also said the resolution "does not increase allowable density anywhere in the city."

The city's chief building official was asked what most limits fourplexes. "Zoning is what restricts fourplexes at this point," he said. His central concern, he said, was making sure "we don't compromise the safety." He said the choice between sprinkler standards would depend on design. The staff draft settles on the residential standards, P2904 or NFPA 13D, with supplemental protection.

The date on the posting

The agenda item suggests a hearing date of "December 3, 2027." The year may be an error: the council is expected to meet Dec. 3, 2026, when data center rules could also come up for a vote. The council sets the actual date when it votes on Nov. 19, so watch that vote for the final date.

What's next

After the hearing, the council would vote on an ordinance adding Appendix BP to City Code Chapter 25-12. Staff contacts listed on the item are in Austin Development Services.