ADU & Garage Conversion Checker

Thinking of a backyard cottage, a garage conversion or an in-law suite? Answer a few questions and get a green, yellow and red checklist, a rough cost range and your next steps.

1. Where is the project?

Is the lot inside City of Houston limits?

2. What are you building?

Project type

Finished size

sq ft

Will it have a kitchen?

3. Rules and the lot

Deed restrictions or HOA rules on second dwellings or garage use

Room on the lot for the new building and setbacks

Flood zone

Will the required off-street parking still fit on the lot?

4. Building details

Garage ceiling height

Garage slab

Escape window for any bedroom

Insulation and heating/cooling for the new space

5. Utilities and use

Utilities and street address

Who will live there?

Your checklist

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Rough cost range

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Next steps

Planning guide only, not legal advice or a permit decision. Rules change. Confirm with the Houston Permitting Center or your city before you spend money on design or construction.

How to read the checklist

✓ Likely OK nothing in your answers suggests a problem, though you still need a permit.
! Check you need to confirm something before you commit.
✕ Likely blocker this will probably stop the project or add major cost unless it changes.

Where this page cannot verify a specific number for your lot, it says to check with the Houston Permitting Center instead of guessing.

City of Houston rules in plain words

No zoning, but deed restrictions matter. Houston does not zone land use. Deed restrictions (rules recorded against your subdivision) fill that role. The City requires a declaration with a building permit that the work will not violate deed restrictions, and the City's Legal Department can sue to enforce certain restrictions, including limits on use, setbacks, and the size, type and number of structures. Neighbors and civic associations can enforce them too. Sources: City of Houston Legal Department, Deed Restrictions and Code of Ordinances Chapter 10 (Sec. 10-3 and Article XV).
Secondary dwelling units (Chapter 42). One primary home plus one secondary dwelling unit can be a single-family lot under Chapter 42. In September 2023 City Council raised the maximum size of a second dwelling unit from 900 to 1,500 sq ft and tied parking to unit size. The changes took effect November 27, 2023, apply to development and redevelopment inside the city limits, and keep deed restrictions in force. Source: City of Houston Planning and Development press release, Sept. 27, 2023.
Off-street parking (Chapter 26). A single-family home needs 2 off-street spaces. Under Sec. 42-186 as amended in 2023, if the main house already has its 2 spaces, a second unit of 1,000 sq ft or less needs no additional space, and one of 1,001 to 1,500 sq ft needs 1 additional space. We confirmed these thresholds in the City's March 2023 draft ordinance text and in news coverage of the final vote; the signed ordinance (No. 2023-801) is a scanned image we could not search, so confirm your case with the Houston Permitting Center. Sources: Planning Dept., Chapter 42 amendments (Ord. 2023-801) and Code of Ordinances Chapter 26, Parking.
Garage conversions. A garage conversion is a change of use that needs a residential permit with plan review, and the City reviews the site plan against the development and parking rules, so lost parking generally has to be replaced on the lot. See the Houston Permitting Center's residential plan review page.
Floodplain (Chapter 19). Since 2018, new buildings in the 100-year or 500-year floodplain must be built 2 feet above the 500-year flood elevation, and so must residential additions larger than 1/3 of the existing footprint (and substantial improvements in the 100-year floodplain). Smaller residential additions in the 100-year floodplain need 1 foot above the 100-year elevation; in the 500-year floodplain there is no elevation requirement for them or for substantial improvements. Substantial improvement means improvement cost of 50% or more of the structure's market value. Source: Freese and Nichols summary of the Houston Chapter 19 changes; the City of Houston Chapter 19 guidelines summary has the elevation table, and the ordinance text is in the City Code of Ordinances. Look up your zone on FEMA's Map Service Center.

Building code basics (apply almost everywhere)

Ceiling height: at least 7 feet in habitable rooms (IRC R305).
Room size: a habitable room other than a kitchen is at least 70 sq ft with no dimension under 7 feet (IRC R304).
Bedroom escape opening: at least 5.7 sq ft net clear, 24 in minimum height, 20 in minimum width, sill no higher than 44 in (IRC R310). Test your window with our Egress Window Checker.
Garage next to living space: a fire-rated separation is required wherever a garage remains attached (IRC R302.6).
Energy code: new living space must be insulated and conditioned to the energy code your jurisdiction has adopted.

Reference: IRC R310, Emergency escape and rescue openings. Your city may adopt a different edition or local amendments, so the permit office has the final word.

Other cities

Choose "Other city" for general guidance. Most cities regulate ADUs and garage conversions through zoning, with limits on where they are allowed, size, height, setbacks, parking and sometimes owner-occupancy. A growing number of states and cities have passed laws that make ADUs easier to build, so check both your state and your city. This tool does not state any rule for a specific city outside Houston.

Where the cost ranges come from

Published 2025 to 2026 ranges per finished square foot, before extras, and they vary by region, finishes and site:

Project	Per sq ft	Typical size used
Detached backyard ADU	$150 to $250	600 sq ft
Garage conversion	$50 to $200	400 sq ft
Attached addition / in-law suite	$150 to $300	500 sq ft
Apartment above a garage	$100 to $300	500 sq ft

Sources: HomeGuide, ADU cost (detached ADU and garage conversion), Angi, cost to build a garage with an apartment and HomeAdvisor, in-law suite cost. These are national averages, not Houston bids. A garage conversion with a kitchen and bath, a flood-zone site or a structural upgrade can run above these ranges. Get local quotes.

This tool is general information, not legal, engineering or permit advice. Always confirm requirements with the Houston Permitting Center or your local building department.

Estimates only — not engineering, legal or code advice. Check requirements with your local building department and a licensed professional before you build.

Common questions

Can I build a backyard ADU in Houston?

Often yes. Houston has no zoning, so the City does not limit land use the way most cities do. Chapter 42 of the Code of Ordinances allows a secondary dwelling unit, with a maximum size of 1,500 square feet since amendments took effect November 27, 2023. But deed restrictions on your street can still forbid a second dwelling and are enforceable, so check them first, along with flood status, parking and a building permit.

Do I need a permit to convert my garage in Houston?

Yes. Turning a garage into living space is a change of use and needs a residential permit with plan review at the Houston Permitting Center, plus electrical, plumbing and mechanical permits for that work. The space has to meet the same code as a new room: ceiling height, insulation, ventilation and, for a bedroom, an escape window.

Do I have to replace the parking if I convert my garage?

Usually yes. Houston's Chapter 26 requires off-street parking for a single-family home (2 spaces), so spaces lost in a garage conversion generally must be provided elsewhere on the lot, for example a carport or driveway space. Confirm the exact requirement for your lot with the Houston Permitting Center before you design.

What is the minimum ceiling height for a converted garage?

The model residential code (IRC R305) requires at least 7 feet in habitable rooms. Many garages are 8 feet or more, but a new floor and insulation take a few inches. Under 7 feet is a serious problem because the fix is raising the roof or lowering the floor.

Does a bedroom in a converted garage need an escape window?

Yes. Sleeping rooms need an emergency escape and rescue opening. Under the model code (IRC R310) it needs at least 5.7 square feet of net clear opening, at least 24 inches high and 20 inches wide, with the sill no higher than 44 inches above the floor.

Can I build an ADU in a floodplain?

Sometimes, but it is harder. In Houston, Chapter 19 requires new buildings in the 100-year and 500-year floodplains (and larger additions and substantial improvements in the 100-year floodplain) to be built 2 feet above the 500-year flood elevation. Converting a garage into living space in a flood zone is often not allowed unless the floor meets the required flood elevation. Check your address on FEMA's flood map and talk to the City's floodplain staff.