What is the 2026 cost range for a interior conversion scope adu in Phoenix?

$76,500-$161,500, with the median landing near $119,000. The range reflects finish tier and layout complexity within the interior conversion scope; the Phoenix labor multiplier of 0.85× vs national median is baked in.

How long does a interior conversion scope adu take in Phoenix?

14-20 weeks of on-site construction for the interior conversion scope, plus 2-6 weeks of permit review in Phoenix if the scope requires a permit. Cosmetic-only refreshes often skip permits; anything touching plumbing, electrical, or structural does not.

What is the single biggest budget-overrun risk for this scope?

Existing slab without a vapor barrier — vapor-pressure moisture leads to flooring failure and mold if not re-poured or sealed. Adds $4-8K.

ADU — Interior conversion Cost in Phoenix, 2026

Low

$77K

$76,500

Median

$119K

$119,000

High

$162K

$161,500

Scope timeline: 14-20 weeksPhoenix permit window: 2-6 weeksUpdated 2026-04-24

Why interior conversion × Phoenix produces this band

A interior conversion scope for a adu in Phoenix combines two price levers: scope and metro labor rates. Interior-conversion ADUs repurpose an existing enclosed space (attached garage, basement) without adding foundation or framing footprint. Faster and cheaper than a detached build. Against the national median remodel labor rate, Phoenix runs 15% below the national median — so the interior conversion band comes in 50% below the mid-range, then scales 15% below the national median on top of that. Permit timelines for residential work in Phoenix typically run 2-6 weeks, which is the window you plan your design and decision sequence against. This page gives you the actual 2026 Phoenix bands for this exact combination, plus the three cost drivers Baily asks about first when scoping the project live.

What drives cost for a interior conversion scope

·Insulation and conditioned-space HVAC tie-in
·Egress window cutting and well install
·Kitchen and bath rough-ins (often net-new to the space)
·Legal separation from the primary unit

What makes Phoenix different

Labor — Non-union market with high trade availability outside of the May-September summer peak.
Labor — Summer heat (115°F+) shifts exterior trades to before-dawn shifts, adding 10-15% scheduling complexity.
Labor — HOA architectural review in 60%+ of the metro runs in parallel with the City permit and doesn't add cost but adds weeks.
Material — Desert-specific materials (reflective roofing, low-UV exterior finishes) carry a small premium.
Material — Regional lumber supply from California and Pacific Northwest — pricing tracks LA trends loosely.

Phoenix rules that affect this scope

City of Phoenix Planning and Development Department runs plan check through Phoenix PDD Online — residential turnaround 2-6 weeks.
Arizona ROC licensing is tiered (Residential Class A/B/C, KB-1 General Building, KB-2 Residential Remodeling) with bond scaling.
Maricopa County Environmental Services governs septic on homes outside sewer service (common in Ahwatukee, Desert Ridge).
Arizona HB 2720 (2024) preempts many local restrictions on ADUs + casitas — opening more inventory for conversion.

Scope your adu with Baily.

Baily asks the eight questions that determine where your project lands inside the $77K-$162K band for Phoenix and hands the scoped brief to one licensed builder.

Loading chat…

Phoenix remodel cost hub →Back to all cost guides →Ask Baily about your project →

Questions LA homeowners actually ask

$76,500-$161,500, with the median landing near $119,000. The range reflects finish tier and layout complexity within the interior conversion scope; the Phoenix labor multiplier of 0.85× vs national median is baked in.