ADU in Carrollton, TX
ADU design and permitting in Carrollton typically runs $8,000-$22,000 for the full permit set, depending on whether you’re converting an existing garage or building a new detached unit. Most Carrollton jobs we take on involve 1970s-80s brick ranch homes where the attached two-car garage becomes the ADU footprint, or backyards that can clear the rear setback on 8,000-plus square foot lots. The work here is shaped by two things more than anything else: Blackland Prairie clay soil that moves, and a county line that splits the city in half. Call (971) 497-2402 and we’ll give you a written price before anything starts.
Why Carrollton Homes Are Different
Most of Carrollton’s housing stock was built between the late 1960s and early 1990s. That means single-story brick ranch homes on generous lots, many of them with attached two-car garages that convert cleanly because there’s no second story bearing down on the structure. The south and central neighborhoods in particular tend to have the kind of deep backyards that make a detached ADU feasible without a rear setback variance, which is not something you can say about the tighter subdivisions in newer outer-ring DFW suburbs.
The soil underneath most of this city is expansive Blackland Prairie clay. It swells in spring rain and shrinks hard during July and August heat. A detached ADU slab that is not engineer-designed for that movement will crack within a few seasons, and doors will start binding. That single fact changes the foundation spec on nearly every new-build ADU we do in Carrollton, and it’s why a garage conversion here is rarely just drywall and paint. The other local wrinkle: Carrollton straddles Dallas and Denton counties. The county line runs through active neighborhoods, and we have caught permit applications filed with the wrong entity on more than one project. It matters which side of the line your ADU footprint falls on, because easement and inspection rules change.
Our Main Carrollton Services
Carrollton homeowners call us about two ADU paths more than any other, and both make practical sense given the local housing stock and lot sizes.
Garage Conversion ADU in Carrollton
A garage conversion in Carrollton takes the existing attached two-car garage on a 1970s or 80s ranch home and converts it into a permitted dwelling unit, typically keeping the existing foundation as the starting point. The single-story construction of these homes means the garage walls and roof line were never engineered for a second floor, so the conversion is straightforward from a structural standpoint. We still verify the slab thickness and condition before committing to a design, because Blackland Prairie clay has shifted more than a few of these slabs since the Nixon administration. Full details on the process, the permit path, and the price ranges are on our Garage Conversion ADU in Carrollton page.
New Detached ADU in Carrollton
A new detached ADU in Carrollton is a standalone unit built in the backyard, and on an 8,000 to 12,000 square foot lot in south or central Carrollton there is usually room to build one without asking the city for a setback variance. The concrete work on these builds gets more attention than a garage conversion does, because the expansive clay under Carrollton demands an engineered slab with proper pier depth. We also design the HVAC as an independent mini-split or ducted system from day one, because a detached unit baking through a 100-degree north Texas summer cannot ride on the main house system. The full scope, including modular options we coordinate through a single contract, lives on our New Detached ADU in Carrollton page.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
ADU Design & Permitting in Carrollton
ADU design and permitting in Carrollton is the phase where the project either becomes a clean build or a six-month headache, and the local conditions make getting the drawings right more important than in most other DFW suburbs. A 1970s ranch home’s existing garage slab was never engineered for the soil movement we see between spring and August, so the permit set has to address foundation specs and HVAC independence from the first sheet. We handle the drawings, the permit package, and the construction under one contract at one written price, which means when the city questions a detail there is no designer pointing at a builder. You can see the full scope on our ADU Design & Permitting page, and the work is always governed by The Haven Standard: a written price before work starts, a documented photo record on every visit, and a 365-Day Done Right Promise in writing.
Site Assessment
Signs you need it
You’re looking at a garage conversion on a home built before 1990 and you don’t know whether the slab is thick enough or whether the county line puts you in Dallas or Denton jurisdiction.
What it costs in Carrollton
A full site assessment in Carrollton runs about $500-$1,800 depending on whether we’re pulling a soil sample or just measuring slab depth and set back distances.
How we do it
We walk the lot, measure the existing slab where one exists, check the county designation for the address, and document everything with photos you receive as part of the visit record.
ADU Design & Blueprints
Signs you need it
You know the ADU you want, but the city requires a stamped permit set, and you don’t have drawings that show foundation, electrical, plumbing, and HVAC as installed systems rather than suggestions.
What it costs in Carrollton
ADU design and blueprints in Carrollton typically run $2,500-$9,000 depending on whether the unit is a garage conversion or a new detached build with its own foundation design.
How we do it
Our studio designs the full set in house, including the engineer’s foundation detail for Blackland Prairie clay and a mini-split or independently ducted HVAC layout, then runs the drawings through Carrollton’s plan review process.
Permit Application
Signs you need it
You’re caught in the Dallas-versus-Denton county line question and you don’t want to burn three weeks resubmitting a package that was filed with the wrong jurisdiction.
What it costs in Carrollton
Permit application as part of a full design and permitting package runs in the $8,000-$22,000 range for the complete set, including drawings, submittals, and city coordination;
How we do it
We prepare the full package for the correct county and city entity, submit it, and manage the review comments back and forth until the permit is issued.
What ADU Design & Permitting Costs in Carrollton
| Item | Typical range in Carrollton |
|---|---|
| Full design + permit set (garage conversion) | $8,000-$18,000 |
| Full design + permit set (new detached) | $12,000-$22,000 |
| Site assessment (standalone) | $500-$1,800 |
How long does ADU permitting take in Carrollton?
Plan review in Carrollton generally runs 4 to 10 weeks depending on jurisdiction and current caseload. Filing with the wrong county entity adds weeks, which is why we verify the straddle line before submittal. Call (971) 497-2402 for a written timeline on your specific address.
Do I need a soils report for a garage conversion ADU in Carrollton?
Not always. We evaluate the existing slab and the home’s settlement history first. A detached new build almost certainly needs an engineered foundation detail for expansive clay. We’ll tell you which applies after the site assessment.
Junior ADU & Interior Conversion in Carrollton
A Junior ADU in Carrollton converts space already inside the house, attached to it, or above a garage into a separate legal dwelling with its own kitchen and entrance, typically in the $30,000-$85,000 range. The 1970s-80s ranch stock here is actually well-suited to this because so many of these homes have underused bedrooms, oversized garages with attic space above, or attached additions that can be legally separated into an independent unit. We run the full process under the same one-contract model as our larger builds, with the Junior ADU & Interior Conversion scope covering everything from drawings to final inspection.
Above-Garage ADU
Signs you need it
You have an attached two-car garage with unused attic space above it that could become a one-bedroom unit with a side entrance.
What it costs in Carrollton
An above-garage ADU in Carrollton typically runs $85,000-$180,000 all-in, because the garage roof structure usually needs reinforcement and you’re adding a full independent HVAC system.
How we do it
We assess the garage roof framing, design the reinforcement, and run separate electrical and mini-split HVAC so the unit does not lean on the main house for comfort during a Texas summer.
Interior JADU
Signs you need it
You have a primary bedroom suite, a floor plan with an underused side of the house, and relatives who need to live close but not in the same room.
What it costs in Carrollton
An interior JADU that converts existing square footage inside a Carrollton home typically runs $30,000-$85,000, with the final number tied to plumbing and whether you’re adding a kitchenette or a full kitchen.
How we do it
We wall off the secondary entrance, add the cooking and bathing fixtures required by the city, and ensure the JADU has its own independently controlled comfort system.
What Junior ADU & Interior Conversion Costs in Carrollton
| Item | Typical range in Carrollton |
|---|---|
| Interior JADU (existing square footage) | $30,000-$85,000 |
| Above-garage ADU | $85,000-$180,000 |
| Room-to-ADU conversion with kitchen + bath | $30,000-$85,000 |
Does a JADU in Carrollton need its own HVAC system?
Yes, in practice. A closed-off interior space sharing the main house’s ducted system will be uncomfortable and we will not design it that way. A mini-split solves the comfort and the code issue. Call (971) 497-2402 and we’ll quote it line by line.
Can an interior JADU be permitted in a Carrollton home built in the 1970s?
A 1970s or 80s-build home can host a JADU. The main constraints are ceiling height in the converted area and access to a legal secondary exit. We verify both during the site assessment.
ADU Site Prep & Utilities in Carrollton
ADU site prep and utilities in Carrollton is where expansive clay, county-line easements, and older electrical panels meet, and it is the phase that can quietly add $35,000 to a project if nobody looked at the ground before the drawings went in. The work covers grading and foundation prep, electrical panel upgrades, plumbing laterals, gas line extensions, and the final site work that brings the ADU online as a legal, inspectable unit. Everything we do in this phase is included under the same single written price as the design and build, which means nobody discovers a surprise panel upgrade at the drywall stage and hands you a change order. You can see the full scope on our ADU Site Prep & Utilities page, and it’s always covered by Haven Standard Clause 1: the price is written before work starts.
Foundation & Grading
Signs you need it
You’re building a detached ADU anywhere in Carrollton and you need the slab engineered for the clay movement that has already cracked driveways and door frames in your neighborhood.
What it costs in Carrollton
Foundation and grading for a new detached ADU on Carrollton’s expansive clay typically runs $10,000-$30,000 depending on slab size, pier depth, and whether grading is needed to direct water away from the structure.
How we do it
We bring in a soils engineer, design the slab for the specific plasticity of your lot’s clay, and grade the pad so water moves away from the finished unit instead of pooling at the slab edge.
Electrical Panel Upgrade
Signs you need it
Your 1970s-era home still has a 100-amp panel and you’re adding a full ADU with its own kitchen, mini-split, and laundry; the math does not work.
What it costs in Carrollton
An electrical panel upgrade in Carrollton, either a subpanel for the ADU or a full main panel replacement, runs $2,000-$8,000 depending on the existing panel’s condition and distance to the new unit.
How we do it
Our electrician verifies the panel rating and existing load, then installs the subpanel or replacement and terminates the ADU’s circuits under a permit we pull and an inspection we sit through.
Plumbing Lateral
Signs you need it
The ADU is going in the backyard and you need a new sewer or water line run from the main house to the unit, or you’re on the wrong side of the county line and the easement rules are different from what the plumber assumed.
What it costs in Carrollton
A plumbing lateral for an ADU in Carrollton runs $5,000-$13,000 depending on the distance from the main line, the soil conditions, and whether trench work crosses a county easement boundary.
How we do it
We scope the trench path before we quote, confirm which county entity governs the easement, and run the line with the inspector present so the inspection passes the first time.
What ADU Site Prep & Utilities Costs in Carrollton
| Item | Typical range in Carrollton |
|---|---|
| Foundation & grading (new detached) | $10,000-$30,000 |
| Electrical panel or subpanel upgrade | $2,000-$8,000 |
| Plumbing lateral (sewer/water tie-in) | $5,000-$13,000 |
Will the Dallas-Denton county line affect my ADU utilities in Carrollton?
It can. Easement widths, inspection schedules, and even the entity that receives your permit application differ by county. We verify the address’s county designation before we file. Call (971) 497-2402 for the right answer on your specific lot.
Do I need a panel upgrade for a garage conversion ADU in Carrollton?
Usually yes. Most 1970s and 80s Carrollton homes carry 100-amp panels, and adding an ADU with a mini-split and kitchen pushes the total load past safe capacity. We check the panel during the site assessment and include the upgrade in the written price.
Brands We Service in Carrollton
We specify and coordinate prefab and modular systems from Abodu, Cover, and Dvele within our Carrollton projects, and we handle the local site work, utilities, and permit package so the factory and the foundation stay aligned under one written price. For a fuller picture of the systems we coordinate, visit our brands.
Pricing for ADU in Carrollton, TX
| Service | Typical range in Carrollton |
|---|---|
| Full design + permit set (garage conversion) | $8,000-$18,000 |
| Full design + permit set (new detached) | $12,000-$22,000 |
| Site assessment (standalone) | $500-$1,800 |
| Garage conversion ADU (all-in) | $110,000-$200,000 |
| New detached ADU (all-in) | $180,000-$400,000 |
| Interior JADU | $30,000-$85,000 |
| Above-garage ADU | $85,000-$180,000 |
| Foundation & grading (new detached) | $10,000-$30,000 |
| Electrical panel or subpanel upgrade | $2,000-$8,000 |
| Plumbing lateral | $5,000-$13,000 |
What pushes a Carrollton price up is usually the soil. An engineered slab on expansive clay costs more than a standard slab and there is no honest way around it. What pushes it down is a garage conversion that reuses the existing footprint and existing walls instead of starting from dirt. Every line item above is a written price before any work starts, per Haven Standard Clause 1, and it does not change at the door.
Neighborhoods We Serve in Carrollton
We work throughout Carrollton, including the older ranch-home streets near Josey Lane and Belt Line where multigenerational households are the norm and the ADU is often planned from the start. Response time across the city runs the same day for a phone quote and within a week for the site assessment.
- North Carrollton
- Downtown Carrollton
- Coyote Ridge
- Castle Hills
- Homestead
Service Area - Cities Near Carrollton
Our crews serve homes throughout the north DFW corridor, and we regularly schedule ADU work in Coppell, TX, Richardson, TX, Lewisville, TX, and Plano, TX. The same written-price, one-contract model applies regardless of which city the project sits in.
Serving Carrollton, TX - Our Local Coverage Area
We’re based in the Carrollton area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs About ADU in Carrollton
Yes. Every garage conversion, new detached ADU, and JADU in Carrollton requires a permit. The city also cares which side of the Dallas-Denton county line the address sits on, because the filing entity changes. We file under the correct jurisdiction the first time. Call (971) 497-2402 for a free estimate on the full permit path.
The clay expands and contracts with seasonal moisture, which cracks undersized slabs and throws door frames out of square. A new detached ADU needs an engineered slab designed for this movement. We bring in a soils engineer on every new-build foundation and include that work in the written price.
We work throughout the entire city, from Downtown Carrollton up to Castle Hills and across to the Josey Lane corridor. The lot size and the county designation matter more than the neighborhood, and we verify both before we quote anything.
What happens when you call
- 1A real person answersNo phone trees - talk to a local adu pro.
- 2You get an upfront price rangeHonest numbers before anyone is dispatched. No surprises.
- 3We come out and measureLicensed & insured, at a time that suits you - the visit and the quote are both free.
- 4You get the price in writingLine-itemed, yours to keep, and nothing starts until you say go.
What Carrollton Customers Say
"Garage conversion finished on the drawings and close to the schedule. They were honest that the sewer connection was the unknown, and it was."
- Arjun D."The permit set and the build were one contract with one number. Our neighbours used two firms and spent a year watching them blame each other."
- Helena V."The rental income has covered the payment since the second month. They were realistic about the numbers rather than optimistic."
- Odette N.