How much does a garage conversion ADU cost in Spokane?

A typical Spokane-area garage conversion runs 100,000 to 200,000 dollars as of 2026. It is often less expensive than a new detached ADU because it reuses an existing structure, but the range is wide and depends on the condition of the garage and how much new plumbing, electrical, insulation, and finish work is needed.

Why is a garage conversion usually cheaper than building new?

The foundation, walls, and roof already exist, so you avoid much of the shell and site work that a new detached unit requires. The savings shrink if the slab, framing, or ceiling height need significant work to meet residential code.

What can make a garage conversion more expensive than expected?

Common surprises include a slab that needs to be raised or replaced, low ceiling height, adding a compliant foundation, long plumbing runs to reach a new kitchen and bathroom, electrical service upgrades, and drainage fixes. An assessment by the builder identifies these early.

Guide

Garage conversion cost in Spokane (2026)

Converting a garage into an ADU reuses a structure that is already standing, which often makes it one of the lower-cost ways to add a unit. This guide explains the work, what moves the price, and how it compares with building new. Figures are dated planning ranges, never quotes.

Get matched with a builder Full ADU cost guide

Typical garage conversion cost in Spokane

Cost is a range tied to the condition of the existing garage and the scope of the conversion. The figure below is a typical Spokane-area planning range with a stated date. It is a planning range, not a quote.

Typical Spokane-area garage conversion: 100,000 to 200,000 dollars, as of 2026.

A typical Spokane-area range as of 2026. Actual cost depends on the condition of the garage, the slab and ceiling height, utility runs, and finishes, and is never a quote or a guarantee. Confirm with your matched builder.

What the cost covers

Insulating the walls, floor, and roof to meet residential energy code.
Adding or extending plumbing for a kitchen and bathroom.
Upgrading electrical service, outlets, and lighting.
Heating and cooling for a living space.
Replacing the garage door with a framed wall, windows, and an entrance.
Addressing the slab, foundation, and drainage where needed.
Interior finishes: flooring, cabinets, counters, and fixtures.
Design, engineering, and permit fees.

What drives the price up or down

Slab and foundation. A sound, level slab keeps cost down. Raising or replacing it adds cost.
Ceiling height. Some older garages are below residential minimums and need structural changes.
Plumbing distance. The farther the new kitchen and bath are from existing lines, the more it costs.
Electrical capacity. A panel or service upgrade may be required.
Finish level. Entry-level versus high-end finishes change the total significantly.

How it compares with a new detached ADU

A garage conversion generally costs less than a comparable new detached unit because it reuses the shell, but a detached unit offers more design freedom and is not limited by the existing structure. If the garage has a failing slab, low ceilings, or sits where an ADU is not allowed, the cost gap can narrow. Our Spokane ADU cost guide compares all four types side by side.

Parking and rules to confirm

Converting a garage removes covered parking, which can interact with parking rules in your jurisdiction. Confirm the current parking and setback standards on your jurisdiction page before you plan a conversion.

Garage conversion cost questions

How much does a garage conversion ADU cost in Spokane?: A typical Spokane-area garage conversion runs 100,000 to 200,000 dollars as of 2026. It is often less expensive than a new detached ADU because it reuses an existing structure, but the range is wide and depends on the condition of the garage and how much new plumbing, electrical, insulation, and finish work is needed.
Why is a garage conversion usually cheaper than building new?: The foundation, walls, and roof already exist, so you avoid much of the shell and site work that a new detached unit requires. The savings shrink if the slab, framing, or ceiling height need significant work to meet residential code.
What can make a garage conversion more expensive than expected?: Common surprises include a slab that needs to be raised or replaced, low ceiling height, adding a compliant foundation, long plumbing runs to reach a new kitchen and bathroom, electrical service upgrades, and drainage fixes. An assessment by the builder identifies these early.

References and primary sources

Regulatory and fee specifics on this page are cited to the current primary sources below. Confirm any figure against its source for your specific parcel before you rely on it.

City of Spokane (my.spokanecity.org) Permit fees and parking rules for conversions.
Spokane County Building and Planning (spokanecounty.gov) County fees and standards.
City of Spokane Valley (spokanevalleywa.gov) Spokane Valley fees and standards.

ADU type

Get matched with a Spokane ADU builder

Tell us about your lot and project. We connect you with a licensed local builder who serves your jurisdiction. It is free to you, with no obligation.

Get matched

Updated July 2026