Building Types | Codes
Texas Building Codes for a Duplex, Triplex or Fourplex
Zoning tells you how many homes a lot may hold. The building code tells you how each home must be built. In Texas, the code changes between two and three units. State law treats a duplex as residential, built under the International Residential Code (IRC). A triplex or fourplex with stacked units or shared exits is commercial, built under the International Building Code (IBC), with a different energy code and, at four units, federal accessibility rules. This page sets out the state minimums and what each city can add.
Texas building codes in six facts
- The state minimum residential code for Texas cities is the International Residential Code (IRC) as it existed on May 1, 2012. The commercial minimum is the International Building Code (IBC) as of the same date. Source: Local Gov. Code 214.212 and 214.216
- Texas law defines "residential" as a detached one- or two-family dwelling, or townhouses of no more than three stories with separate exits. A multifamily building outside that definition is "commercial." Source: Local Gov. Code 214.211
- Since January 1, 2009, a Texas city may not require a fire sprinkler system in a new or existing one- or two-family dwelling. Source: Occupations Code 1301.551(i)
- One- and two-family homes of three stories or fewer follow the energy chapter (Chapter 11) of the 2015 IRC, the state standard since September 1, 2016. Source: State Energy Conservation Office
- Other residential buildings follow the 2015 International Energy Conservation Code (IECC), the state standard since November 1, 2016. Source: State Energy Conservation Office
- Under the federal Fair Housing Act, ground floor units in buildings of four or more units, and every unit in such a building with an elevator, must meet accessible design rules. Source: 42 U.S.C. 3604
Which Rules Apply to Each Building
| Building | Code family | State energy standard | City sprinkler rule | Federal accessibility |
|---|---|---|---|---|
| Duplex (two-family dwelling) | Residential: IRC, state minimum as of May 1, 2012 | 2015 IRC Chapter 11 | A city may not require them | Fair Housing Act design rules start at 4 units |
| Townhouses, up to 3 stories, each with its own exit | Residential: IRC, under the state definition | Ask the city which state energy standard it applies | Set by the city's adopted codes | Fair Housing Act design rules start at 4 units |
| Triplex with stacked units or shared exits | Commercial: IBC, state minimum as of May 1, 2012 | 2015 IECC | Set by the city's adopted codes | Fair Housing Act design rules start at 4 units |
| Fourplex with stacked units or shared exits | Commercial: IBC, state minimum as of May 1, 2012 | 2015 IECC | Set by the city's adopted codes | Ground floor units must meet the design rules (all units if there is an elevator) |
Sources: Local Gov. Code chapter 214, Occupations Code 1301.551, SECO single-family and commercial code pages, 42 U.S.C. 3604. The code family column is VanPlex's reading of the state definitions; confirm it with your city's building official.
The State Minimum Codes
Texas sets a floor for city building codes. Under Local Government Code 214.212, "the International Residential Code, as it existed on May 1, 2012, is adopted as a municipal residential building code in this state." Section 214.216 does the same for the International Building Code as the municipal commercial building code. A city may adopt later editions and local amendments by ordinance after a public hearing.
Larger cities must give extra notice. Under Section 214.217, a city of more than 100,000 people must post notice on its website on or before the 21st day before its council acts to consider adopting or amending a national model code, such as the IRC, the IBC or the National Electrical Code. It must hold a public hearing if five or more people ask for one. Read your city's code adoption ordinance to learn which edition applies to your permit.
Why a Third Unit Changes the Code
The answer is in two definitions in Local Government Code 214.211. "Residential" means "having the character of a detached one-family or two-family dwelling or a multiple single-family dwelling that is not more than three stories high with separate means of egress." A multiple single-family dwelling is a row of townhouses, and a means of egress is the exit path out of a home. "Commercial" includes "a residence if the building is a multifamily residence that is not defined as residential by this section."
Under these definitions, a duplex is residential. Side-by-side townhouses of three stories or fewer, each with its own exit, are residential too. A triplex or fourplex with units stacked on top of each other, or with units sharing a stair or corridor, does not fit the residential definition, so it is commercial and follows the IBC. VanPlex could not open the International Code Council's own text of the IRC scope section, so this is a reading of the Texas statute. Ask your city's building official which code your design falls under before you pay for drawings.
Fire Sprinklers
Texas bars cities from requiring sprinklers in one- and two-family homes. Under Occupations Code 1301.551(i), "after January 1, 2009, a municipality may not enact an ordinance, bylaw, order, building code, or rule requiring the installation of a multipurpose residential fire protection sprinkler system or any other fire sprinkler protection system in a new or existing one- or two-family dwelling." A duplex falls inside that rule.
The ban covers one- and two-family dwellings only. For townhouses and buildings of three or more units, sprinkler rules come from the residential, building and fire codes your city has adopted. Ask the city fire marshal or building official before design starts.
Energy Codes
Texas has two state energy standards, set by the State Energy Conservation Office (SECO) in the Comptroller's office. For one- and two-family homes of three stories or fewer, SECO adopted the energy chapter, Chapter 11, of the 2015 IRC, effective September 1, 2016, according to its single-family code page. For commercial buildings and other residential buildings, SECO adopted the 2015 International Energy Conservation Code (IECC), effective November 1, 2016. Its commercial code page says the code "applies to R2, R3 and R4 residential buildings and excludes single and two-family residences of three stories or fewer above grade." R2, R3 and R4 are residential classes in the building code. The page adds that SECO continues with the 2015 IECC.
State law limits how often the residential standard can change. Under Health and Safety Code 388.003, SECO may adopt a newer edition only after a finding on how strict it is and an analysis of its effect on housing cost, no more often than once every six years, and with an effective date at least nine months after adoption. SECO's updated adoption process took effect September 1, 2025: commercial codes are reviewed on a three-year cycle and residential codes on a six-year cycle.
Accessibility at Four Units
The federal Fair Housing Act sets design rules for "covered multifamily dwellings." Under 42 U.S.C. 3604(f)(7), those are all units in buildings of four or more units that have one or more elevators, and ground floor units in other buildings of four or more units. The rules apply to buildings "for first occupancy after the date that is 30 months after September 13, 1988," which is March 13, 1991. A new fourplex therefore has covered ground floor units.
Covered units must have accessible public and common areas, doors wide enough for wheelchairs, an accessible route into and through the unit, light switches and outlets in reachable places, reinforced bathroom walls for later grab bars, and kitchens and bathrooms a wheelchair user can use. A duplex or triplex has fewer than four units and falls outside these rules.
Texas adds its own law. The Texas Architectural Barriers Act, Government Code chapter 469, is enforced by the Texas Department of Licensing and Regulation (TDLR). It covers publicly funded buildings and privately funded "public accommodations" and "commercial facilities" as the Americans with Disabilities Act (ADA) defines them. Plans for a covered building with an estimated construction cost of at least $50,000 must go to TDLR, and a city may not accept the building permit application until the project is registered. Whether a small private rental building, or its leasing office, is covered is a legal question. Ask TDLR or a Registered Accessibility Specialist before you submit plans.
Single Stairs and Backup Power (2025)
Two 2025 laws touch small apartment buildings. SB 2835 lets a city allow an apartment building with one stairway if it has no more than six stories above grade, no more than four units on any floor, sprinklers, two-hour rated stair enclosures with no elevator opening into them, no more than 20 feet from any unit door to the stair, and no more than 125 feet of exit travel. The law says a city "may authorize" this, so ask whether yours has.
SB 1252 added Local Government Code 214.214(d), which bars a city from amending the National Electrical Code to regulate how a residential energy backup system is installed or inspected, except a city-owned utility in its service area. The other 2025 laws page has both bills.
Plan Review, Inspections and Deadlines
Under Local Government Code 214.904, a city must grant or deny a permit application within 45 days, send written reasons why it cannot decide yet, or agree on a deadline; after a reasons notice it has 30 more days. If it misses the deadline, it may not collect the permit fees and must refund fees already paid.
HB 14 (2023) created Local Government Code chapter 247 for outside review. If the city does not act on a development document by the 15th day after its legal deadline, a licensed engineer or another listed reviewer may do the review. If it does not conduct a required inspection within 15 days after its deadline, an inspector certified by the International Code Council or a licensed engineer may inspect. SB 1202 (2025) extended the chapter to home backup power installations and bars a city from charging a fee for any third-party review or inspection under it.
On the coast, owners who need wind coverage from the Texas Windstorm Insurance Association (TWIA) must also meet windstorm codes. The Texas Department of Insurance adopted the 2024 IRC and IBC as its windstorm building codes, effective April 1, 2026, according to its windstorm codes page. The insurance and flood page explains which counties need a windstorm certificate.
Best For
- ✓ Duplex owners: residential code, no city sprinkler mandate, no Fair Housing Act design rules.
- ✓ Townhouse rows of three stories or fewer where each home has its own exit.
- ✓ Small apartment builders in cities that allow the SB 2835 single-stair option.
Usually Fails When
- ✕ A triplex or fourplex is designed to the residential code when its stacked units make it commercial.
- ✕ A fourplex plan leaves out the accessible ground floor units the Fair Housing Act requires.
- ✕ The design assumes a single stair in a city that has not authorized it.
What To Verify Before Spending Money
- → Which IRC and IBC editions and local amendments your city has adopted.
- → Whether your design is residential or commercial, confirmed with the city building official.
- → Whether the project must register with TDLR, confirmed with TDLR or a Registered Accessibility Specialist.
Where to Go Next
Related on VanPlex: the Texas multiplex guide overview and the missing middle guide for how Canadian codes treat small multiplexes.
Frequently Asked Questions
Is a triplex built under the IRC or the IBC in Texas?
Do townhomes need fire sprinklers in Texas?
Can a Texas city require fire sprinklers in a duplex?
What energy code applies to a duplex in Texas?
What energy code applies to a fourplex in Texas?
Does the Fair Housing Act apply to a fourplex?
Do I need TDLR registration for my Texas project?
What building code edition is the Texas minimum?
Can a Texas city adopt a newer building code than the state minimum?
How much notice must a Texas city give before adopting a new building code?
What happens if a Texas city is late reviewing my plans?
Official sources (checked October 2026)
Planning a multiplex in Texas?
VanPlex builds multiplexes and models lots in British Columbia, Canada. We do not build, lend, or broker in Texas yet. Join the Texas list and we will tell you when that changes.