Garage/Office Conversion

Boss PDX converts garages into offices, ADUs, and living space across the Portland metro. We're a licensed Oregon (CCB #232383) and Washington (BOSSPPL793RN) general contractor, in business since 2020, with a fixed written scope and one lead carpenter plus one project manager assigned to your job start to finish. Portland's ADU-friendly zoning — particularly under the Residential Infill Project — has made garage conversions one of the fastest-growing remodeling categories in the metro. Whether you're adding a rental ADU, a home office, or an in-law suite, we handle the full scope from design through final inspection. Why Portland Homeowners Are Converting Garages Portland has led the Pacific Northwest in accessory dwelling unit policy for over a decade. The city dropped system development charges for ADUs, eliminated off-street parking requirements for ADU conversions, and with the Residential Infill Project (effective August 2021) opened most residential lots to additional density. That policy environment, paired with Portland's housing shortage and rising property values, has made garage conversions one of the most practical ways to add square footage, rental income, or multigenerational living space without buying a bigger house. A detached garage sitting at the back of a standard Portland lot — the classic 20-by-22 two-car footprint — already has a foundation, a roof, and walls. Converting that structure into conditioned space costs substantially less per square foot than building new, because excavation, foundation, framing, and roofing are either done or require only modification. For homeowners who want the $800 to $1,500+ per month a well-built Portland ADU can generate in rental income, a garage conversion is often the shortest path from underused space to real value. Types of Garage Conversions Garage-to-ADU (Rental Unit or Guest House) The most involved and most valuable conversion we build. Under Portland's ADU code and Oregon's statewide ADU legislation (HB 2001), a garage-to-ADU creates a self-contained dwelling unit with its own kitchen, bathroom, sleeping area, and separate entrance. It's reviewed by the Portland Bureau of Development Services (BDS) and requires building, electrical, plumbing, and mechanical permits. This is the right path when the goal is rental income or fully independent living space. Learn more on our ADU contractor page . Home Office or Studio The most common "dry" conversion — no new plumbing. The scope covers insulation (floor, walls, ceiling), drywall, flooring, electrical circuits, HVAC, and replacing the garage door with a framed wall and windows. Office and studio conversions move faster and cost less than ADU-grade conversions because they skip plumbing rough-in, kitchen finish, and separate-entrance requirements. In-Law Suite An in-law suite sits between a basic office conversion and a full ADU in scope and cost. It typically includes a bedroom, a bathroom (sometimes ADA-accessible), and a small living area — private enough for a parent or family member, but without the separate kitchen and entrance of a full ADU. Plumbing scope adds cost, but avoiding the kitchen buildout and separate utility considerations keeps the number below a full ADU conversion. Home Gym, Bonus Room, or Flex Space Not every garage conversion needs to meet ADU standards. A finished bonus room — insulated, drywalled, heated — adds functional square footage for a gym, art studio, music room, or playroom. These conversions still require a building permit in Portland (any work that changes the thermal envelope or adds electrical circuits triggers permits), but the review is lighter and the timeline shorter. Structural Requirements A garage was built to park cars, not house people. Every conversion starts with an assessment of what the existing structure can support and what needs to change. Foundation and Floor System Most Portland garages sit on a slab poured without insulation, without a vapor barrier, and at a grade lower than the house floor. Converting to habitable space under Oregon's energy code requires insulating the floor assembly — typically by building a framed floor on top of the slab with rigid foam insulation, or in some cases breaking out and re-pouring with below-slab insulation. The approach depends on ceiling height: adding 4 to 6 inches of floor buildup in an 8-foot-ceiling garage can push the finished ceiling below code minimum. Garage Door Replacement Removing the garage door and framing in the opening is one of the most visible parts of any conversion. The new wall needs a structural header sized for habitable-space loads (many older Portland garages have undersized headers). The framed wall typically includes windows for natural light — Portland code requires minimum window area for habitable rooms — and often a person door for ADU or in-law suite conversions. We match siding, trim, and roofline to the existing house so the conversion reads as original. Our framing contractors page covers more about structural framing work. Wall and Ceiling Work Garage walls are typically uninsulated single-stud framing with exposed studs or unfinished drywall. Converting to living space requires insulating all exterior walls to current code, adding a vapor barrier, and installing finished drywall. If the garage shares a wall with the house and the conversion is an ADU, one-hour fire-rated assembly is required on the shared wall. Insulation Requirements in Portland's Climate Portland sits in Climate Zone 4C under the Oregon Residential Specialty Code, and the insulation requirements for converting unheated garage space are substantial. Floor assemblies need a minimum R-10 rigid foam. Exterior walls require R-21 (2x6 walls) or R-13 plus continuous exterior insulation (2x4 walls) — most garage walls are 2x4, so meeting the R-value often involves adding continuous rigid insulation before finishing with drywall. Ceilings with attic space above get blown-in insulation to R-49; cathedral ceilings need spray foam or rigid foam between rafters. Proper air sealing is as important as insulation value — Portland's wet climate creates condensation risk in poorly sealed assemblies. Electrical, Plumbing, and HVAC A typical garage has one or two circuits. Converting to living space requires dedicated circuits for outlets, lighting, and HVAC equipment, plus kitchen appliance circuits for ADU conversions. Most garage conversions need a new subpanel fed from the house's main panel. For plumbing, dry conversions skip it entirely; ADU and in-law suite conversions add bathroom and kitchen lines, which means trenching through the slab or running lines under a raised floor system. Distance from the garage to the house's main sewer line affects cost directly. For HVAC, a ductless mini-split heat pump is the most common solution in Portland garage conversions — it provides heating and cooling on a dedicated circuit, installs without ductwork (preserving ceiling height), and handles Portland's mild but variable climate efficiently. Portland Permitting for Garage Conversions Change of Occupancy Converting a garage (utility/storage occupancy) to habitable living space (residential occupancy) is a change of occupancy under the Oregon Residential Specialty Code. BDS reviews plans for structural adequacy, fire separation, egress, ventilation, energy efficiency, and accessibility — whether you're building an ADU or just finishing a bonus room. ADU Permitting and the Residential Infill Project If the conversion includes a kitchen, it's reviewed as a full ADU. Portland's ADU rules, bolstered by Oregon's statewide mandate and the Residential Infill Project (RIP), have streamlined the path — no conditional use permit, no owner-occupancy requirement, no off-street parking replacement in most zones. RIP also changed the density math: on most R5 and R2.5 lots, converting a detached garage to an ADU no longer counts against a restrictive unit cap. We submit and manage the full permit package — architectural plans, structural engineering, energy compliance, and trade permits — so you're not navigating the BDS queue yourself. Lot Coverage and Parking Portland zoning limits lot coverage (typically 45% in R5 zones). An existing garage already counts toward coverage, so converting it doesn't usually change the calculation — the footprint stays the same. Parking is a practical consideration rather than a permit blocker: Portland eliminated off-street parking requirements for ADUs in most zones, but if you're converting the only garage, you'll need a plan for your cars. Some homeowners add a carport or expanded driveway pad alongside the conversion. Garage Conversion Cost in Portland Basic Living Space (Office, Gym, Bonus Room) A dry conversion typically runs $30,000 to $80,000 for a standard two-car garage. The range depends on floor system complexity, finish level, and the electrical upgrade needed. Full ADU Conversion (Kitchen, Bathroom, Separate Entrance) A complete garage-to-ADU — kitchen, bathroom, living/sleeping area, separate entrance, subpanel, dedicated HVAC — typically costs $80,000 to $200,000+ depending on the garage's starting condition, utility connection complexity, and finish level. The return can be substantial: a Portland ADU renting at $1,200 to $1,500/month generates $14,400 to $18,000 annually, and the added square footage increases property value. More on ADU scoping at our ADU contractor page . We don't quote a garage conversion off a phone call — we walk the space, confirm what the foundation and framing can support, and hand you a fixed written estimate before anything is signed. Start at our garage conversion estimate form or the general free estimate form . Garage Conversion Timeline A basic dry conversion typically takes 4 to 8 weeks of construction after permits are issued, with permit review adding 2 to 6 weeks. ADU-grade conversions take 8 to 16 weeks of construction with 4 to 10 weeks of BDS plan review. Total project timelines run 3 to 4 months for a dry conversion and 5 to 8 months for a full ADU . Construction follows a predictable sequence: demo, foundation/floor work, framing, rough-in trades, insulation, drywall, finish trades, and final inspections. We build every job around a fixed scope with no surprise phases. Frequently Asked Questions Do I need to replace the garage door with a wall, or can I keep it? For any conversion to habitable space, the garage door must be removed and the opening framed with a proper insulated wall. Even an insulated garage door doesn't meet the thermal, structural, or air-sealing requirements for a conditioned space. The new wall typically includes windows for natural light (required by code for habitable rooms) and often a person door for separate-entrance conversions. Will converting my garage affect my property taxes? Converting a garage to habitable space increases the assessed improvement value of your property, which typically results in a property tax increase. In Multnomah County, the increase is based on added real market value, subject to Oregon's Measure 50 limits on assessed value growth. An ADU conversion triggers a larger reassessment than a simple office conversion. The tax increase is usually modest relative to the value gained — especially for ADU conversions generating rental income. Can I convert a detached garage close to my property line? Yes, in most cases. Portland's ADU setback rules allow detached ADUs as close as 5 feet from side and rear property lines. An existing garage within those setbacks is typically grandfathered for its current footprint. If the garage is closer than 5 feet to a property line, fire separation requirements (fire-rated wall, no openable windows on that side) apply. We confirm setback compliance during our initial site assessment. Does my garage need a separate address and utility meters for an ADU? Portland requires a separate address for an ADU (assigned by BDS during permitting), but separate utility meters are not required in all cases. Water and sewer can typically share the existing house connection. Electrical can share via a subpanel, though some homeowners opt for a separate meter to simplify tenant billing. We coordinate address assignment and utility requirements as part of the permit package. What happens to my homeowner's insurance? You need to notify your insurance carrier when you convert a garage to living space. The conversion changes the use and value of the structure, and an undisclosed conversion could void coverage. If the conversion is an ADU for rental use, your carrier will likely require a landlord endorsement or separate policy. Proper permits and inspections make the insurance conversation straightforward — we provide the final inspection documentation your carrier needs. Can I convert only half of my garage and keep parking? Partial conversions are possible but come with constraints. The converted portion must meet all habitable-space requirements, and the remaining garage must maintain fire separation — typically a one-hour fire-rated wall and self-closing fire-rated door. This separation requirement adds cost and eats floor area. In many cases, converting the full garage and solving parking with a carport or driveway expansion is more cost-effective than splitting the space. Why Boss PDX for Your Garage Conversion Boss PDX has handled garage conversions and home additions across the Portland metro since 2020, working with a bench of 41 named trade partners listed on our partners page . Every job gets a fixed written scope, one lead carpenter, one project manager, and a same-day reply to your first call. We pull and manage all permits, coordinate every inspection, and hand you a finished space that passes final with no open items. Call us at 844-BOSS-PDX (844-267-7739) or request a free estimate online to start the conversation. One call, straight answers, no obligation.