What Affects the Cost of Hiring an ADU Builder in Texas?

6-minute read

Thursday, July 24, 2025

ADU “cost” usually comes down to project scope — the total work a builder must plan, coordinate, and build. Change the scope, and the workload changes (and that’s exactly what experienced adu builders are sizing up from day one).

Here are the biggest scope drivers for detached ADUs, attached ADUs, and garage conversions in Texas — no price talk, just what really moves the work.

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Quick answer: the biggest cost drivers

What “hiring an ADU builder” really includes

Scope choices that move the work up or down

How ADU type changes the scope

Design choices that add steps, coordination, or labor

How to keep your scope clear when talking to builders

Ready to Build? We’re Here to Help

Frequently Asked Questions

Quick answer: the biggest cost drivers

ADU type: detached, attached, or garage conversion
Size and layout complexity
Bathrooms and plumbing distance
Ceiling height and structural changes
Accessibility requirements
Utility limitations (electric, sewer vs septic, long tie-ins)
Finish level (standard vs custom)
Local permitting steps and inspections

What “hiring an ADU builder” really includes

A tiny house plan featuring a kitchen and living room, available for sale.

Hard scope vs planning scope

Many builds include coordination work beyond the job site: confirming what’s included, lining up trades, planning inspections, and managing change requests so the plan stays consistent.

Why permitting steps affect effort and timing

Permits add applications, plan review responses, and inspections. Steps vary by city. Austin’s ADU page shows how a city can require portal filings and scheduled inspections (Austin Additional Dwelling Units process).

Scope choices that move the work up or down

Utility tie-ins and distance to hookups

Longer tie-ins can add routing work and surface restoration, and tight access can change the approach.

Service connections and approvals

If you’re on septic, extra approvals may be needed. The Texas Commission on Environmental Quality notes permits and approved plans are required to construct, alter, repair, extend, or operate an on-site sewage facility (TCEQ on-site sewage guidance).

Electric service and meter setup

Some homes can support added electrical demand; others need service or metering changes. Oncor publishes Electric Service Guidelines used for planning service equipment and installations (Oncor Electric Service Guidelines PDF).

How ADU type changes the scope

Detached ADU

Often a full “new build” package in a smaller footprint, plus complete utility runs.

Attached ADU

Adds integration with the main home and more coordination around an occupied structure.

Garage conversion

Reuses the shell, but existing conditions can add upgrades like insulation, moisture control, and new openings.

Design choices that add steps, coordination, or labor

Rooflines, windows, and exterior details

More roof breaks and exterior transitions add detail work; cleaner shapes are usually simpler.

Custom interiors and built-ins

Custom cabinetry, built-ins, and tile-heavy areas add fit and finish steps.

Mechanical choices

HVAC and ventilation choices affect equipment placement and routing – especially in tight conversions.

How to keep your scope clear when talking to builders

A simple scope checklist to bring to calls

ADU type and rough room list
Bathrooms (count) and laundry (yes/no)
Utility notes (sewer vs septic, panel location, tie-in distance)
Accessibility needs
Finish direction (standard vs custom)

Questions to ask so you get apples-to-apples proposals

What’s included and excluded?
Who coordinates permits and inspections?
What assumptions are you making about utilities and access?
How do you handle scope changes?

Ready to Build? We’re Here to Help

Want help turning these scope decisions into a clear plan? Visit Small House Solutions ADU Builders to see how our design-build team supports Texas homeowners from early feasibility through permitting and construction – and book a consultation when you’re ready.