What's Required in Houston
- A lot with one house plus a detached secondary dwelling unit of not more than 900 sq ft is single-family residential (Chapter 42)
- One additional off-street parking space for a secondary dwelling unit of 900 gross sq ft or less (Chapter 42)
- Detached unit: New Residential Construction permit with the Residential Prerequisite Checklist (CE-1301); plan review 15 business days
- Garage conversion: residential remodel/conversion permit; attached unit: residential addition permit (10 business days)
- Fee: square-footage tier ($47 base + $5.36 per 8.17 sq ft after 57.16 sq ft, wood frame) + 25% plan review + $33.56 admin; trade permits separate
- Dwelling requirements: bedroom egress windows, hardwired interconnected smoke detectors, 3-ft entry door, one-hour fire wall within 5 ft of the property line
- Trade permits by TDLR master electricians, TSBPE master plumbers and TDLR Class A/B A/C contractors registered with the city
- Deed restrictions are enforced by the city; storm water, floodplain and planning reviews apply by project type
Can You Build an ADU in Houston?
Yes, and without a zoning fight, because Houston has no zoning. The city's development rules in Chapter 42 of the Code of Ordinances call the unit a secondary dwelling unit and treat a lot with one free-standing house and a detached secondary dwelling unit of not more than 900 square feet as still single-family residential. The same chapter requires two off-street parking spaces per dwelling unit but only one additional space for a secondary dwelling unit of not more than 900 gross square feet, and in special minimum lot size areas it limits a lot to one primary dwelling plus one secondary dwelling unit of not more than 900 square feet. What can stop an ADU is not the city but the subdivision: Houston's Legal Department enforces deed restrictions, and many neighborhoods restrict second units, so the city tells you to confirm your deed restrictions before you build.
Houston ADU Permit Rules by Scenario
| What you are doing | City filing | Rule |
|---|---|---|
| Detached backyard unit or garage apartment, up to 900 sq ft | New Residential Construction permit with 15-business-day plan review | HPC New Residential Construction (HPWCODE 1136); Chapter 42 |
| Converting an existing detached garage into a dwelling | Residential remodel or conversion permit with plan review | HPC Residential Remodel Permit (HPWCODE 1135) |
| Attached unit built as an addition | Residential Addition permit with 10-business-day plan review | HPC Residential Addition Permit (HPWCODE 1134) |
| Parking | One additional off-street space for a unit of 900 sq ft or less | Chapter 42, parking for single-family residential uses |
| Unit within 5 ft of the property line | One-hour fire-rated wall on that side | Residential Permitting 101, basic code requirements |
| Kitchen and bath plumbing, wiring, HVAC | Separate plumbing, electrical and mechanical permits by registered licensees | Residential Permitting 101, licensing |
| Lot in a deed-restricted subdivision that bars second units | City enforces the restriction; check before designing | Top 10 sheet item 3 |
How Much Does an ADU Permit Cost in Houston?
A detached unit is new residential construction, priced on the 2026 Building Code Enforcement fee schedule's one- and two-family residential table, which charges by square footage rather than by job value (Texas HB 852 bars valuation-based residential fees). For wood-frame construction (Type VB) the second tier is a $47.00 base charge plus $5.36 for each additional 8.17 square feet after the first 57.16 square feet, up to 1,224.89 square feet where the third tier begins. A 900-square-foot unit therefore carries a permit fee of about $604, a non-refundable plan review fee of 25 percent ($151) and the $33.56 administrative fee, roughly $789 for the building permit; a 600-square-foot garage apartment is about $530. Trade permits are separate and each carries its own admin fee: plumbing fixtures at $34.24 for one to three with a $97.56 minimum, electrical with a $91.06 minimum plus $94.00 for a new meter loop, and HVAC at $11.41 per ton plus $47.00. Impact fees, utility taps and the designer's fee are on top of that.
Who Files an ADU Permit in Houston?
The building permit may be purchased by the owner, agent or contractor; Houston does not license general contractors. New construction is filed in iPermits with the building permit application, the Declaration in Support signed by the owner and validated against Harris County Appraisal District records, a complete set of plans and the Residential Prerequisite Checklist (CE-1301). Plan review on new residential construction is listed at 15 business days, and a legal survey is required at the first structural inspection. Trade permits are then pulled by master electricians licensed by TDLR, master plumbers licensed by the Texas State Board of Plumbing Examiners and A/C contractors with a TDLR Class A or B license, each registered with the city. The city's basic-requirements list applies to the unit as a dwelling: egress windows in bedrooms, hardwired interconnected smoke detectors, a 3-foot-wide entry door, and a one-hour fire-rated wall within 5 feet of the property line.
Outside Reviews
New construction in Houston passes through more than Building Code Enforcement: the Residential Permitting 101 guide lists Planning, taps and meters, floodplain, traffic and storm water reviews by project type, and single-family lots of 15,000 square feet or more, or over 65 percent impervious cover, need a Storm Water Information Form. Sidewalks are required on major thoroughfares, inside the 610 Loop and on lots over 125 feet of frontage, and a driveway or curb cut needs a bonded contractor.
How to Get a ADU Permit in Houston
Check deed restrictions and the plat
Houston has no zoning; the subdivision's deed restrictions and plat building lines decide whether and where a second unit can go.
Design to Chapter 42 and the checklist
900 sq ft or less, one added parking space, egress windows, interconnected smoke detectors, fire-rated wall within 5 ft of the line.
File in iPermits
New residential construction (detached) or remodel/addition (attached or converted), with the Declaration in Support, plans and the Residential Prerequisite Checklist. Owner, agent or contractor may apply.
Pay and wait for review
About $789 for a 900 sq ft building permit including plan review and admin; new construction review is 15 business days.
Trade permits, inspections, survey
Registered electrician, plumber and A/C contractor pull their permits; a legal survey is required at the first structural inspection; inspections next business day.