The Short Answer
Garage conversion cost is set less by square footage than by what the finished room has to do. A heated office with new walls, lights and outlets is one project. A bedroom that needs an egress window is a bigger one. Add a bathroom and you are cutting the slab for drains. Add a kitchen and separate entrance and you are usually building an accessory dwelling unit (ADU), with its own permit path and costs.
The existing shell — foundation, walls, roof — is why converting a garage is often less expensive than a ground-up home addition. But garages were built to store cars, not people. The slab usually slopes to the door, the walls are often uninsulated, and there may be no heat, plumbing or spare electrical capacity. Bringing those up to the standard for living space is where the money goes.
Scope sets the price: office, bedroom, bedroom plus bath and ADU are four different budgets.
The slab matters most: its level, slope, moisture and height relative to the house drive floor costs.
Bedrooms need egress: a sleeping room needs a code-compliant emergency escape opening.
Plumbing is the big jump: a bathroom means drains, venting and often slab cutting.
Permits are required: both Portland and the City of Vancouver require a building permit to convert a garage to living space.
Garage Conversion Scopes, From Simplest to Most Involved
Before comparing prices, decide which of these you are actually pricing. Most confusing quotes come from comparing different scopes.
| Scope | Typical work involved |
|---|---|
| Finished room — office, gym, playroom, family room | Insulation, drywall, flooring, electrical circuits and lighting, heating and cooling, garage door opening infilled |
| Bedroom or guest room | Everything above, plus a code-compliant emergency escape opening and smoke alarm coverage |
| Bedroom or suite with a bathroom | Everything above, plus drain, vent and supply lines — usually through the slab — and bathroom ventilation |
| Garage ADU | A complete, separate dwelling: living and sleeping space, kitchen, bathroom, its own entrance, plus the separation and utility requirements for a second unit |
A garage office conversion is usually the most modest scope, because it needs no plumbing and no egress opening for sleeping. A garage to bedroom conversion adds the escape opening and, in most cases, a wall with a window where the garage door was. Each step up adds real work rather than finish upgrades.
What Does a Garage Conversion Cost? Published Benchmarks
No single figure fits every garage, but two published references give a starting frame.
National benchmark. This Old House's garage conversion cost guide, updated June 2026 and built on Homewyse, Angi and Home Depot data, puts typical conversions at roughly $9,659–$51,659, with its most basic tier covering insulation, drywall, flooring, simple electrical and minimal window work. See This Old House: Garage Conversion Cost.
Serden Group's published ADU planning ranges. For a permitted garage conversion ADU — a full dwelling unit, not a single room — our ADU page lists $70,000–$160,000 for a 350–600 sq ft unit. Our Vancouver ADU page uses the same garage-conversion range, and our Portland ADU page lists $85,000–$200,000 for basement or garage conversions in Portland, where older housing stock and permit and system development charges push costs higher.
These two references describe very different projects. The national figure is an average across simple and complex rooms nationwide; the ADU ranges are for complete, permitted dwelling units with a kitchen and bathroom. A single finished room in the Vancouver–Portland metro will usually fall somewhere between them, but neither number is a quote. The only reliable price for your garage comes from a written estimate based on its actual condition.
What Drives the Cost to Convert a Garage Into Living Space
The slab: level, slope, moisture and height
Garage slabs are typically sloped toward the door for drainage and often sit below the floor of the house. You have three broad choices: level the slab and finish directly over it, build a framed floor system on top to bring it up to the house's floor height, or cut and repour sections. A raised floor solves the step into the house and creates room for insulation, but it costs ceiling height. Moisture coming up through the slab has to be addressed before any finished flooring goes down.
Insulation and the energy code
Most garage walls and ceilings are uninsulated, and some garage walls are not deep enough for the insulation required for conditioned space. Adding conditioned space triggers current energy code requirements for the walls, ceiling and floor. Expect insulation, air sealing and possibly furring out walls to be a real line item.
The garage door opening
The opening usually becomes a framed, insulated wall, often with a window or a door. The new wall needs a footing or curb that the inspector accepts, and the exterior has to be finished to match the house — siding, trim and paint. How well the infill matches the rest of the elevation is a design decision with a cost attached.
Egress for sleeping rooms
A bedroom needs an emergency escape and rescue opening — a window or door of a minimum size and sill height. If the garage has no suitable window, that means cutting a new opening in a wall, adding a header, and installing a compliant window. Portland lists egress windows among the most common problems in conversions, alongside ceiling height, stairs, insulation and ventilation.
Ceiling height
Living space has minimum ceiling heights that garages do not always meet, especially once a raised floor is added. As one local example, the City of Vancouver's ADU guidance, in its requirements for interior conversion ADUs, calls for converted living spaces to have a finished ceiling height of at least 6 feet 8 inches and legal egress windows; confirm the figure that applies to your project and jurisdiction. A low ceiling can limit the floor-system choice or the whole project.
Heating, cooling and ventilation
Extending existing ductwork is not always possible or sensible. Many conversions use a separate system such as a ductless heat pump. Bathrooms and kitchens need mechanical ventilation.
Electrical capacity
A garage might have a single circuit for lights and an opener. Living space needs properly spaced outlets, lighting, smoke and carbon monoxide alarms, and circuits for heating equipment. If the existing panel lacks capacity, a panel upgrade or service change can become one of the larger costs in the project.
Plumbing and sewer
Adding a bathroom means drains, venting and supply lines. In a slab-on-grade garage, drains are usually installed by cutting a trench in the concrete and connecting to the house's sewer line — the farther and higher that line is, the harder the job. Where gravity drainage does not work, other solutions are needed, each with its own tradeoffs.
Fire separation and property-line walls
If part of the garage stays a garage, the wall and ceiling between the garage and new living space need the separation the residential code requires between a garage and a dwelling. Walls close to a property line can trigger fire-rated construction too: Portland states that any outside wall within three feet of a property line needs fire-rated construction.
Replacement parking and storage
Losing the garage means losing parking and storage. Some homeowners add a shed or storage elsewhere; some jurisdictions have rules about where a replacement parking space can go. In Portland, off-street parking is not required, but the city says that if you remove a garage space and keep the driveway, you must show how a parking space can be provided outside required setback areas, and driveway changes are reviewed by the Portland Bureau of Transportation. See Portland Permitting & Development: attic, basement or garage conversion.
What Garage Conversion Quotes Include — and Leave Out
Two prices for "a garage conversion" can describe very different work. Ask each contractor to state whether these items are in or out.
| Item | What to confirm |
|---|---|
| Design and drawings | Who produces the plans, and whether structural calculations are included if needed |
| Permit fees | Whether building and trade permit fees are included or passed through at cost |
| Floor work | Leveling, a raised floor system, moisture control, and flooring |
| Garage door infill | Footing or curb, framing, window or door, exterior siding and paint |
| Insulation | Walls, ceiling and floor, plus air sealing to energy code |
| Electrical | New circuits, lighting, alarms, and whether a panel upgrade is included |
| Heating and cooling | The equipment type and who installs it |
| Plumbing | Slab cutting, drain connection, venting, fixtures and patching |
| Finishes | Drywall level, trim, doors, paint and fixture allowances |
| Exclusions | Hidden-condition repairs, utility fees, system development charges for ADUs, and taxes |
Allowances deserve special attention. A low quote with small allowances for flooring or fixtures can end up more expensive than a higher quote with realistic ones.
Existing-Condition Assessment Checklist
These are the conditions that most often change the cost of a garage conversion. Many can be checked before design starts:
- How much the slab slopes, whether it is cracked or heaved, and whether it shows signs of moisture
- The height difference between the garage floor and the house floor
- Ceiling height now, and after a raised floor if one is needed
- Wall framing depth and condition, and whether the garage was ever permitted as a structure
- The electrical panel's available capacity and the route to the garage
- The location and depth of the sewer line relative to a possible bathroom
- Water heaters, furnaces or laundry already in the garage that would have to move or be enclosed
- Distance of exterior walls from the property line
- Where parking and storage will go afterward
- Any earlier, unpermitted finish work
That last item matters. Portland states that unpermitted finished space must be permitted as if the work had not been done yet, and that garages built under a permit exemption need full structural review. Opening finished walls for inspection is a cost to plan for, not a surprise to absorb.
Added Living Space vs an Independent ADU
This is the decision that changes the project most, so make it first.
Added living space — a bedroom, office or family room — becomes part of the existing home. It shares the home's kitchen and, usually, its utilities.
An ADU is a separate dwelling. It has its own kitchen, bathroom and entrance, and it can be rented or used for a family member who needs independence. Both Portland and Vancouver handle ADUs through their own permit process. Portland notes that a non-accessory kitchen combined with a bathroom may make converted space an ADU, and that ADUs have their own set of permits; see Portland Permitting & Development: ADUs. The City of Vancouver says an existing garage may be converted into an ADU if it can meet applicable zoning, building and safety standards, and that attached ADUs must be separated from the main unit with 1-hour fire-rated construction and an STC/IIC 45 sound rating; see City of Vancouver: Accessory Dwelling Units.
An ADU also brings costs a bedroom does not, including possible system development charges and utility work. Our guide to the ADU permit process in Clark County and Vancouver walks through that path, and our ADU construction page covers garage-conversion ADUs specifically.
Permits for Garage Conversions in Portland and Vancouver
Portland, OR. Portland Permitting & Development states that you need a building permit to convert a garage to living space, and that electrical, plumbing or mechanical permits may also be needed. The application generally requires a permit application, a site plan and architectural plans, with structural calculations depending on scope. Work is reviewed under the Oregon Residential Specialty Code and Portland's zoning code, and the city allows special standards for some existing conditions. See Portland: attic, basement or garage conversion.
Vancouver, WA. The City of Vancouver lists "converting basement, attic or garage space into a living space" among the projects that need a residential (RES) building permit. See City of Vancouver: Residential Building Permits.
Elsewhere. Camas, Battle Ground, Lake Oswego, the Washington County cities and unincorporated county areas each have their own building departments and rules. Confirm requirements with the department that serves your address before you finalize a design. Requirements change, so treat this section as a starting point rather than a substitute for checking.
Planning Questions to Answer Before You Get Quotes
- What will the room be used for now, and in ten years?
- Does it need a bathroom, or is the house bathroom close enough?
- Will anyone sleep there? If so, plan for egress from the start.
- Is a separate rental or family unit the real goal? If so, price it as an ADU.
- Should the floor match the house level, or is a step acceptable?
- Where will the cars, bikes, tools and seasonal storage go?
- Do you want the exterior to read as part of the house, or is a simpler infill acceptable?
- Would a ground-level addition or a reworked interior layout deliver the space you need better?
Bring the answers, photos of the garage inside and out, and rough dimensions to your first meeting. That turns a general conversation into a useful scope.
Frequently Asked Questions
How much does a garage conversion cost?
It depends mainly on the scope. A finished room with no plumbing is the least expensive version; adding a bathroom, a sleeping room with egress, or a full kitchen raises the cost in steps. One national benchmark, This Old House's June 2026 guide, puts typical conversions at roughly $9,659 to $51,659. For permitted garage conversion ADUs, Serden Group's published planning ranges are $70,000 to $160,000 in Vancouver, WA and $85,000 to $200,000 for basement or garage conversions in Portland, OR. Neither figure is a quote for your garage.
Is it cheaper to convert a garage than to build an addition?
Usually, because the foundation, walls and roof already exist. The savings shrink when the slab needs a new floor system, the walls need significant framing work, or the room needs plumbing run a long distance. Compare both options against the same finished scope.
How much does it cost to convert a garage into a bedroom?
A bedroom conversion costs more than a basic finished room because a sleeping room needs a code-compliant emergency escape opening, and the garage door opening usually becomes a framed wall with a window. Add a bathroom and the cost rises again, mostly from drain and vent work in the slab. The exact number depends on the existing conditions in your garage.
How much does a garage office conversion cost?
An office is usually the most modest conversion scope: insulation, drywall, flooring, electrical circuits, lighting and a heating and cooling solution, with no plumbing. Costs climb when the floor has to be raised or leveled, when the electrical panel lacks capacity, or when the garage door opening is filled with a wall and windows rather than a simpler infill.
Do I need a permit to convert my garage into living space?
In Portland and in the City of Vancouver, yes. Portland Permitting & Development states that you need a building permit to convert a garage to living space, and the City of Vancouver lists converting garage space into living space among the projects that need a residential building permit. Electrical, plumbing or mechanical permits may also apply. Other cities and unincorporated county areas have their own building departments, so confirm with the one that serves your address.
Is a garage conversion the same as an ADU?
No. A garage converted into a bedroom, office or family room is added living space for the existing home. An ADU is a separate dwelling unit with its own living, sleeping, kitchen and bathroom facilities, and it goes through its own permit path. Portland notes that adding a non-accessory kitchen and a bathroom to converted space may make it an ADU.
Where will I park after converting my garage?
Plan this before design. In Portland, the city says off-street parking is not required, but if you remove a garage space and keep the driveway, you need to show where a parking space can go outside required setbacks. Driveway changes are reviewed by the Portland Bureau of Transportation. Requirements differ by jurisdiction, so check yours.
Can an existing unpermitted garage conversion be legalized?
Often it can, but it is treated as new work. Portland states that unpermitted finished space needs the same permits as if the work had not been done, which can mean opening walls so inspectors can see framing, insulation, wiring and plumbing. Budget for that discovery work.
When to Get a Professional Assessment
Get a site visit before you pay for drawings if any of the following apply: you want a bedroom or bathroom, the slab is noticeably sloped or damp, the ceiling is low, the panel is old or full, the garage is close to a property line, or there is earlier unpermitted work. Each can change the scope — and occasionally whether the conversion makes sense at all.
Serden Group plans and builds garage conversions as part of our home additions and ADU work, with an in-house crew supported by licensed, vetted trade partners and one project manager. Homeowners in Clark County can start with home additions in Vancouver, WA or ADUs in Vancouver; Oregon homeowners can see home additions in Portland, OR or ADUs in Portland.
Send photos and rough dimensions, tell us how you want to use the space, and we can walk through the slab, egress, plumbing and permit questions for your garage. Call (360) 836-7775 or request a consultation.
You can also browse our completed remodeling projects.
