Junior ADU & Interior Conversion Cost - One Fixed Price, Permits Handled

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How Much Does Junior ADU & Interior Conversion Cost in Houston?

A junior ADU (JADU) in Houston typically costs $65,000 to $135,000 when built as an interior conversion of existing space – a garage, a large bedroom suite, or an underused bonus room. Most homeowners converting a two-car garage into a JADU with a kitchenette and bathroom land between $85,000 and $115,000. The final number depends on whether you’re converting space that already exists or adding square footage, and whether the home’s plumbing and electrical systems need upgrading to support a second living unit.

A JADU is an accessory dwelling unit contained within the walls of your primary home – typically a garage conversion, a finished-out attic, or a sectioned-off wing with its own entrance and kitchenette. We’re Lodgewick ADU Houston, and we’ve been building junior ADUs and interior conversions across the Houston metro since 2010. Russ Delmar leads our Houston team, and every project we quote comes with a written price before work starts – no exceptions.

Junior ADU & Interior Conversion Cost Breakdown (2026)

Below are the real numbers we’re seeing across Houston in 2026. These ranges come from our own bids and completed projects in neighborhoods like Timbergrove, Meyerland, Garden Oaks, Braeswood Place, and the Heights. Your price will move within these ranges based on the condition of your foundation, your panel’s available amperage, and how far your existing sewer line is from where the new bathroom needs to drain.

Those line items add up fast. A straightforward garage-to-JADU conversion in a 1970s ranch home in Spring Branch, where the panel has room and the bathroom can tie into an existing drain line, usually lands around $75,000 to $85,000. The same project on a pier-and-beam home in the Heights with a 60-amp panel from 1952 can push $125,000. That spread is why we write the price down and hand it to you before any work starts – you should never have to guess where you stand.

The Junior ADU & Interior Conversion in Houston process we run includes a site walk in the first week, a written scope of work, and a fixed price. It’s part of The Kingswell Guarantee: written price first, a real arrival window, a clean job site, and a written guarantee on every project. If something isn’t right, we come back and make it right – free of charge, within the 365-day window.

What Affects Junior ADU & Interior Conversion Pricing in Houston

No two Houston homes price the same. Here are the six things that move your number most.

• Foundation type. Pier-and-beam homes in older neighborhoods like the Heights, Montrose, and Eastwood make running new plumbing and electrical far easier – and cheaper – than slab-on-grade construction common in Katy, Cypress, Pearland, and Sugar Land. Cutting into a slab to move a drain line adds $4,000 to $10,000 to the job.
• Electrical panel capacity. A JADU needs its own circuit for the kitchenette, the bathroom, and the HVAC. Homes built before 1990 in Houston frequently have 100-amp or even 60-amp panels. If yours can’t handle the added load, you’re looking at a subpanel or full service upgrade, which is $2,500 to $7,500 before the JADU work even starts.
• Distance to existing plumbing lines. In a garage conversion, the bathroom and kitchenette need to drain. If the garage sits 15 feet from the main sewer line with a clear crawlspace below, the plumbing is straightforward. If the garage is on the opposite side of the house from the cleanout and you’re on slab, costs climb quickly.
• HVAC requirements. Houston’s 90-plus-degree days from May through September make an unconditioned JADU unlivable and a mold risk. A ductless mini-split handles heating and cooling for most JADUs at $4,000 to $9,000 installed. Tying into your existing central system usually costs less up front but leaves you with uneven temperatures and higher summer electric bills.
• Permit and code requirements. The City of Houston requires permits for any JADU conversion – the plumbing, electrical, structural, and mechanical work all get inspected. Plan review and permit fees run $2,500 to $6,000 depending on scope. Working unpermitted saves money today and creates a mess when you sell or refinance, because unpermitted square footage doesn’t count on the appraisal.
• Interior finish level. A kitchenette with stock cabinets, laminate counters, and a basic fridge lands around $12,000. The same kitchenette with custom cabinets, quartz counters, and a higher-end compact appliance package runs $20,000 to $28,000. Bathroom finishes swing the same way. Your finish choices can move your total by $15,000 to $25,000 on a typical 400-square-foot JADU.

How to Save on Junior ADU & Interior Conversion

The biggest savings come from working with the house you have, not against it. Here’s what actually moves the number down in Houston – and what doesn’t.

• Convert a garage or existing finished space instead of adding on. New construction in Houston runs $180 to $250 per square foot. Converting existing square footage runs $110 to $180 per square foot. A 400-square-foot garage conversion saves $30,000 to $40,000 compared to building a 400-square-foot addition from scratch.
• Keep the kitchenette simple. A JADU legally requires a kitchenette, not a full kitchen. A two-burner electric cooktop, a bar sink, a compact refrigerator, and a 24-inch cabinet run satisfies the requirement at $12,000 to $15,000. Adding an oven, a dishwasher, custom cabinets, and stone counters doubles that. Most renters and family members don’t need the upgrades.
• Tie into existing plumbing wherever possible. If your garage shares a wall with a bathroom or laundry room, route the JADU bathroom against that wall. The savings on drainage work alone can be $3,000 to $8,000.
• Use a ductless mini-split instead of extending central HVAC. Mini-splits cost less to install and operate than running new ductwork. They also let the JADU occupant control their own temperature, which cuts your overall electric bill when the space sits empty.
• Choose mid-grade finishes. You don’t need $8-per-square-foot tile in a rental JADU. Durable LVP flooring at $3 to $5 per square foot installed handles tenants, kids, pets, and Houston humidity. Solid-core doors, shaker-style cabinets, and quartz-look laminate give you a clean, rental-ready space without the premium price.

If you want a real answer for your specific house, call us at (361) 326-2313. We’ll walk the space, talk through what you’re hoping to get out of the JADU – rental income, an aging parent, a returning adult child – and hand you a written price. No charge for the estimate, and nobody changes the price at the door. That’s a Kingswell rule.

What Does a Junior ADU Conversion Include?

A junior ADU is a self-contained living space inside your existing home’s footprint. It has its own entrance, a place to sleep, a bathroom, and a small food-prep area with a sink and cooking appliance. It may or may not share the main home’s HVAC system. Under Houston’s rules, a JADU is capped at 500 square feet and must be within the primary dwelling, not a detached structure.

Here’s what a typical interior conversion includes – and what it doesn’t.

• Included: framing and drywall for the new layout; plumbing for the bathroom and kitchenette; electrical rough-in and fixtures; insulation in walls and ceiling; a separate entrance with a locking exterior door; flooring; paint; a bathroom with shower, toilet, and vanity; a kitchenette with sink, cooktop, and refrigerator; smoke and carbon monoxide detectors as required by code.
• Not always included: a full-size kitchen range or oven; a washer and dryer; separate utility metering; furniture and window coverings; a separate mailbox or address designation.

When we quote a JADU in Houston, the written scope lists every one of these items line by line. You’ll know exactly which finishes are in your number and which ones aren’t. No allowances that “might” cover something. No “we’ll figure it out when we get there.” The Kingswell Way means saying the price before the work, showing up in the window given, leaving the place cleaner than we found it, putting the guarantee in writing, and coming back if it fails.

How Long Does a Junior ADU & Interior Conversion Take in Houston?

A garage or interior JADU conversion in Houston takes 10 to 16 weeks from the day permits are issued to the final inspection. That range assumes the home has adequate electrical capacity and no hidden structural surprises. Add 2 to 4 weeks for plan review and permit approval with the City of Houston, plus another 1 to 2 weeks for owner finish selections if you haven’t chosen your flooring, cabinets, and paint before we start.

Attic conversions run longer – 14 to 20 weeks – because of the structural work, stair access, and the extra inspections that come with modifying rooflines and load-bearing framing. Houston’s building department has been moving faster in 2026 than in prior years, but summer is slam season, and permit review slows down when the volume spikes.

You’ll get a defined arrival window before any crew shows up, and that window is written in your project scope. Our technicians are background-checked and uniformed, so when the doorbell rings at 7:55 a.m. for your 8:00 start, you know exactly who’s standing there.

Is a Junior ADU a Good Investment in Houston?

For most Houston homeowners, yes – and the numbers support it. A 400-square-foot garage conversion that costs $85,000 and rents for $1,100 to $1,400 a month in neighborhoods like Oak Forest, Garden Oaks, or the Heights produces $13,200 to $16,800 a year in gross rent. That’s a 15% to 19% gross annual return. Even after property taxes, insurance, and maintenance, the JADU pays for itself in 6 to 8 years and then throws off cash.

The other use case we see constantly in Houston is multi-generational housing. An aging parent who needs to be close but wants their own door. A college student home from UT or Texas A&M who needs space and structure. A young couple saving for a down payment. The JADU gives them independence without a separate lease, a separate utility account, or a 20-minute drive across town.

One caveat: Houston neighborhoods inside the 610 Loop tend to see stronger rental demand and higher appreciation than far-out suburbs, but they also come with older homes and more expensive remodeling conditions. A JADU in Katy or Cypress costs less to build but typically rents for $900 to $1,100 a month. A JADU in the Heights costs more up front but commands $1,300 to $1,600. Either way, the investment math usually works.

FAQs – Junior ADU & Interior Conversion Cost

How much does a junior ADU cost in Houston in 2026?

A junior ADU in Houston costs $65,000 to $135,000 for most interior conversions, with $85,000 to $115,000 being the typical range for a garage conversion with a kitchenette and full bathroom. Smaller interior room conversions start around $45,000. Call (361) 326-2313 for a written quote specific to your home – estimates are free.

Is it cheaper to convert a garage or build a detached ADU?

Converting a garage is almost always cheaper, at $65,000 to $110,000, versus $150,000 to $250,000 for a detached ADU built new on a Houston lot. The garage already has a foundation, roof, and exterior walls, which saves $40,000 to $80,000 in structure costs. Detached ADUs also require separate utility connections, which adds $10,000 to $20,000 in most Houston subdivisions.

Can you convert my garage into a JADU if it has no plumbing?

Yes. Running new water supply lines and a drain line into a garage costs $4,000 to $12,000 depending on how far the garage sits from the main sewer line and whether your home is pier-and-beam or slab-on-grade. We quote this as a line item in your written estimate, so you’ll know the exact plumbing cost before you commit. Call (361) 326-2313 to schedule a site walk.

Do I need a permit for a junior ADU conversion in Houston?

Yes. The City of Houston requires building, plumbing, electrical, and mechanical permits for any JADU conversion. Plan review and permit fees run $2,500 to $6,000 total. Unpermitted work can’t be counted as living space on an appraisal and creates a disclosure problem when you sell. We handle the permits as part of the job and the cost is included in your written price.

How much does a garage conversion cost per square foot in Houston?

Garage conversions in Houston run $110 to $180 per square foot in 2026, depending on finish level, plumbing complexity, and electrical upgrades. A basic 400-square-foot conversion with standard finishes lands around $130 per square foot, or $52,000 of the total, before any electrical or foundation work. High-end finishes push the per-square-foot number to $180 or more.

Can you come give me a price this week?

Yes. We run site walks across the Houston metro every week – inside the Loop, Spring Branch, Memorial, Sharpstown, Bellaire, Pearland, Katy, Cypress, and beyond. Call (361) 326-2313 and a live person answers, 24/7. We’ll schedule a walk, put the price in writing, and you’ll have your number before any work starts.

Pricing reflects the Houston market as of 2026. Written by Russ Delmar, who leads the Lodgewick ADU Houston team and has overseen junior ADU and interior conversion projects across the Houston metro since 2010. Lodgewick ADU Houston offers free estimates – call (361) 326-2313.