Garage conversion guide
Converting a garage to a permitted ADU — what San Diego and Washington homeowners actually ask.
Real questions homeowners ask before converting a garage into a permitted living unit — answered with contractor-grade detail on costs, code requirements, permitting, and rental income.
These are the exact questions San Diego, Tacoma, and Lakewood homeowners ask before converting a garage into a permitted ADU — covering costs, code requirements, permitting, and what to expect from the process. Written by a CSLB-licensed ADU contractor serving California and Washington.
Section 1 of 5
Feasibility & eligibility
Which garages can be converted, what the code requires, and what stands in the way.
Can I convert my garage into an ADU?
Most attached and detached garages in San Diego County and Pierce County (Tacoma/Lakewood) can be converted into a permitted ADU under current state and local law. California's AB 68 eliminated minimum lot size requirements for garage ADU conversions; the main remaining obstacles are minimum ceiling height (7 feet for habitable space), adequate natural light, and utility access. A structurally sound single-car garage (typically 200–250 sqft) can become a studio ADU; a two-car garage (typically 400–500 sqft) can become a one-bedroom or two-room ADU. We assess feasibility in a free on-site walkthrough.
Does converting my garage into an ADU require replacing the lost parking?
In California, replacement parking is not required when a garage is converted within a half-mile of public transit or in an urbanized area — which covers essentially all of San Diego County under state law. Individual cities cannot impose replacement parking requirements in these areas. In Washington (Pierce County/Tacoma/Lakewood), replacement parking requirements depend on the local ordinance and how many parking spaces the property has currently. We review your specific lot and city requirements at the consultation.
What is the minimum ceiling height for a garage ADU?
California requires 7-foot minimum ceiling height in habitable rooms. Most modern attached garages have 8-foot walls and are straightforward. Older garages with lower ceilings may require raising the roof plate or excavating the floor to meet the minimum — both are possible but add cost. We measure and assess ceiling height at the feasibility walkthrough. Washington (Pierce County) follows the same 7-foot IRC minimum.
What happens to my existing garage door?
The garage door opening is infilled — framed in with structural members, insulated, and finished to match the exterior of the main home. This is a permitted structural change included in the ADU scope. The infill design is reviewed for aesthetic match with the main structure as part of the design phase. Most municipalities require the infill to substantially match the exterior materials and colors of the main home.
Can I convert an attached garage into an ADU without an internal door to the house?
Yes — in fact, a detached entrance is required for legal ADU designation. An attached garage ADU needs its own private exterior entrance. An internal door connecting to the main home may remain (and is required for California JADUs), but for standard ADUs the unit must be independently accessible without going through the main home. We design the entrance location and type as part of the floor plan.
Section 2 of 5
Permitting a garage conversion
What permits are required, how long they take, and what plan check looks for.
What permits are required to convert a garage into an ADU?
A typical garage conversion requires: building permit (structural — framing, garage door infill, roof changes if any); plumbing permit (new kitchen and bath rough-in); electrical permit (new circuits, sub-panel or load calculation, lighting); mechanical permit (HVAC system — mini-split or ducted). California and Washington both require all four for a habitable ADU conversion. We pull every required permit in-house — the permit set is part of our project scope, not an add-on.
How long does permitting take for a garage conversion in San Diego?
San Diego County and city ADU permit processing has improved significantly since state law reforms. Standard garage conversion permit applications typically receive approval in 4–8 weeks from complete submission. Smaller garage conversions sometimes qualify for over-the-counter review (same day or within a week). We submit complete permit sets with thorough plan check responses, which minimizes correction cycles and keeps the timeline close to the advertised target.
Will my garage conversion be inspected?
Yes — multiple times. Required inspections typically include: foundation/slab (if any excavation), framing, rough plumbing, rough electrical, rough mechanical, insulation, drywall, and final building inspection. Washington adds a fire-stopping inspection between the converted garage and any adjacent conditioned space. We schedule every required inspection as part of the project timeline — you're never responsible for managing inspection scheduling.
What does plan check look for in a garage conversion permit set?
Key plan check review items for a garage ADU conversion: ceiling height compliance, natural light (minimum 8% of floor area in natural light), ventilation, egress (properly sized exit doors and emergency egress windows in sleeping areas), energy compliance (Title 24 in California, Washington energy code), plumbing fixture count and supply line sizing, electrical load calculation, smoke and CO detector placement, and fire separation between the ADU and any attached structure. A well-prepared permit set anticipates all of these. Incomplete sets generate correction cycles and delay — we submit complete.
Section 3 of 5
Garage conversion costs
What a permitted garage conversion costs and what drives the number.
How much does a garage conversion cost in San Diego?
Permitted garage conversion costs in San Diego in 2025–2026 typically run $80,000–$160,000 for a full conversion with kitchen, bath, and private entrance. A basic studio conversion (kitchenette, no separate bedroom, shower-only bath) on the lower end; a one-bedroom with full kitchen and bath on the higher end. Key cost drivers: condition of the existing garage structure, plumbing distance from main house sewer and water stubs, electrical panel capacity, and finish level. We give you a full line-item breakdown in the written proposal before any commitment.
How much does a garage conversion cost in Tacoma or Lakewood?
Garage conversion costs in Pierce County (Tacoma/Lakewood) typically run $65,000–$130,000 for a full permitted conversion — about 10–20% lower than San Diego due to lower regional labor and material costs. Pierce County permitting fees are also lower than California jurisdictions. The same cost drivers apply: existing structure condition, utility hookup distances, and finish level.
Why does a garage conversion cost less than a new detached ADU?
The shell already exists — you're not paying for a new foundation, new framing, a new roof, or new exterior walls. The cost savings come from reusing the existing structure. The remaining cost is in the systems (plumbing, electrical, HVAC), the garage door infill, insulation and weatherproofing to bring the space to habitable code, and the interior finish. A garage conversion typically costs 40–60% of a comparable new detached ADU.
What are the biggest surprise costs in a garage conversion?
The most common unexpected costs: (1) Substandard existing framing that needs supplementation or replacement to meet current code — older garages in particular. (2) Electrical panel capacity — if the main house panel is already at capacity, a sub-panel or panel upgrade is required. (3) Plumbing distance — the further the garage is from the main house sewer stub, the more pipe and trenching is required. (4) Low ceiling height — raising the roof plate or excavating the floor. (5) Asbestos or lead paint in pre-1980 garages. The feasibility walkthrough surfaces all of these before the written proposal is issued.
Section 4 of 5
Rental income from a garage ADU
What garage ADUs earn and how the numbers work.
How much can I rent a converted garage ADU for in San Diego?
A permitted converted garage studio or one-bedroom ADU in San Diego County rents for $1,400–$2,400/month depending on neighborhood, size, and finish quality. Neighborhoods with strong rental demand — Chula Vista, North Park, Carlsbad, Encinitas, Clairemont — command the higher end. Garage ADUs are particularly attractive to single tenants or couples who value privacy and a private entrance. At $1,800/month, a $100,000 conversion delivers an 18% gross yield before expenses — one of the strongest risk-adjusted returns in residential real estate.
How much can I rent a converted garage ADU for in Tacoma or Lakewood?
Pierce County garage ADU rentals currently run $900–$1,500/month depending on location and size. Proximity to JBLM, downtown Tacoma, or major employers pushes toward the high end. The demand base from military and defense-sector renters is consistent. At $1,200/month on a $90,000 conversion, the gross yield is approximately 16%.
How quickly can I start renting after the conversion is complete?
Once the final inspection is passed and the certificate of occupancy is issued, the unit is legally habitable and can be rented immediately. We coordinate the final inspection directly and give you advance notice of the expected final date so you can advertise the unit, screen tenants, and have a lease ready to execute. The goal is zero days between final inspection and first rent check.
Section 5 of 5
The conversion process
What happens, in what order, and what to expect.
What is the step-by-step process for a garage ADU conversion?
A full permitted garage conversion typically follows this sequence: (1) Feasibility walkthrough and written proposal (1–2 weeks). (2) Design and permit set preparation (2–4 weeks). (3) Permit submission and plan check (4–8 weeks in San Diego; 6–10 weeks in Tacoma/Lakewood). (4) Permit issuance and project kickoff. (5) Demo and site prep (1 week). (6) Structural work — garage door infill, any ceiling or framing modifications (1–2 weeks). (7) Plumbing and electrical rough-in (1–2 weeks). (8) Inspections. (9) Insulation and drywall (1–2 weeks). (10) Finish — flooring, kitchen, bath, fixtures, paint (2–4 weeks). (11) Final inspection. Total: 3–6 months start to finish.
Can I live in my home during the garage conversion?
Yes — garage conversions are far less disruptive than a whole-home remodel. The active construction is contained to the garage structure. You lose parking (if it was a parking garage) and will have some noise and dust during active phases, but your home remains fully habitable throughout. We sequence the work to minimize disruption and give you advance notice of the days with the highest activity level.
What is the #1 thing to do before starting a garage ADU conversion?
Get a feasibility assessment from a licensed ADU contractor — not a general remodeler — before any design decisions or financial commitments. The assessment should cover: ceiling height (the most common conversion deal-breaker), structural condition of the existing garage, electrical panel capacity, plumbing stub-out locations, and permit timeline for your specific city. Done in a single on-site walkthrough. Most homeowners who skip the feasibility assessment encounter one of these issues mid-project and pay significantly more to resolve it than if they'd identified it upfront. Our feasibility consultations are free — call us before you commit to anything.
Ready to talk about your project?
Free on-site consultation, written proposal at the end. Call 1-888-484-3132 or book online.