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

$103,500-$218,500, with the median landing near $161,000. The range reflects finish tier and layout complexity within the interior conversion scope; the Chicago labor multiplier of 1.15× vs national median is baked in.

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

14-20 weeks of on-site construction for the interior conversion scope, plus 6-14 weeks of permit review in Chicago 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 Chicago, 2026

Low

$104K

$103,500

Median

$161K

$161,000

High

$219K

$218,500

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

Why interior conversion × Chicago produces this band

A interior conversion scope for a adu in Chicago 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, Chicago runs 15% above the national median — so the interior conversion band comes in 50% below the mid-range, then scales 15% above the national median on top of that. Permit timelines for residential work in Chicago typically run 6-14 weeks, which is the window you plan your design and decision sequence against. This page gives you the actual 2026 Chicago 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 Chicago different

Labor — Union trades (carpentry, electrical, plumbing) are the majority of licensed remodel labor — premium over national median.
Labor — Winter shuts down most exterior trades Dec-Feb, compressing schedules into a 9-month season.
Labor — Chicago Prevailing Wage Ordinance drives labor costs on any publicly-touching work.
Material — Midwest steel and framing lumber are priced competitively vs coasts.
Material — Masonry restoration (common in pre-war Chicago brick) uses specialty materials with long lead times.

Chicago rules that affect this scope

Chicago DOB self-certification is available for registered architects — compresses permit timelines.
Landmark districts (e.g. Lincoln Park, Old Town Triangle) require Commission on Chicago Landmarks review in addition to DOB permit.
Chicago Energy Conservation Code (IECC 2021) applies to all work changing envelope or HVAC.
Two-flat and greystone conversions frequently trigger zoning variance — timeline extension of 8-14 weeks.

Scope your adu with Baily.

Baily asks the eight questions that determine where your project lands inside the $104K-$219K band for Chicago and hands the scoped brief to one licensed builder.

Loading chat…

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

Questions LA homeowners actually ask

$103,500-$218,500, with the median landing near $161,000. The range reflects finish tier and layout complexity within the interior conversion scope; the Chicago labor multiplier of 1.15× vs national median is baked in.