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ADU Construction in San Francisco — Add Space, Value & Income

California's ADU laws have made it easier than ever to build a backyard unit. But easier doesn't mean easy. You need a contractor who's done this before — not one figuring it out on your project.

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More Space. More Value. More Possibilities.

Maybe you need space for aging parents. Maybe you want rental income to offset your mortgage. Maybe your adult kid needs a place while they get on their feet. Or maybe you just want to add $200,000+ to your property value. Whatever the reason, an Accessory Dwelling Unit is one of the smartest investments a San Francisco homeowner can make right now.

California's ADU laws (AB 881, SB 13, AB 68) have dramatically simplified the approval process. San Francisco has streamlined its own rules to encourage ADU development. But 'streamlined' in San Francisco still means navigating DBI permits, planning review, utility hookups, fire setbacks, and building code compliance. The paperwork alone stops most homeowners in their tracks.

Gadget Construction handles the entire ADU process — from initial feasibility assessment through design, permitting, construction, and final inspection. We've built detached backyard units, garage conversions, and basement ADUs across San Francisco. We know what DBI is looking for, which designs get approved faster, and how to avoid the common mistakes that add months and thousands of dollars to ADU projects.

Our ADU Construction Services

Full-service ADU design and build — we manage every phase so you get a finished, permitted unit without the chaos.

Detached Backyard ADUs

New standalone structures built in your backyard — from studio apartments to full 2-bedroom units up to 1,200 sq ft.

Garage Conversions

Transform your existing garage into a finished living space — often the fastest and most cost-effective ADU option.

Basement Conversions

Convert unused basement space into a legal, permitted dwelling unit with proper egress, ventilation, and waterproofing.

Junior ADUs (JADUs)

Up to 500 sq ft carved out of your existing home — an efficient option when lot space is limited.

Full Design-Build

We coordinate architecture, engineering, and construction under one roof — fewer handoffs, fewer delays, fewer surprises.

ADU Costs in San Francisco

Garage Conversion

Existing structure to finished unit

$100,000–$200,000

Junior ADU (within home)

Up to 500 sq ft

$80,000–$150,000

Detached ADU (studio/1BR)

New construction

$200,000–$350,000

Detached ADU (2BR, high-end)

Full design-build

$300,000–$450,000+

Basement Conversion

Including waterproofing and egress

$120,000–$250,000

Prices reflect typical San Francisco market rates. Your exact cost depends on scope, site conditions, materials, and permits. We provide detailed, itemized estimates — no ballpark guesses.

Get Your Exact Price — Free Estimate

Our ADU Process

1

Feasibility Assessment

We evaluate your lot, zoning, setbacks, and utility access to determine what type and size of ADU is possible.

2

Design & Engineering

Architectural plans, structural engineering, and Title 24 energy calcs — all prepared for DBI submittal.

3

Permits

We submit to SF DBI and manage the plan review process. We know what they're looking for and how to get through review efficiently.

4

Construction

Foundation, framing, plumbing, electrical, HVAC, finishes — a complete build with weekly updates.

5

Final Inspection & Certificate of Occupancy

All city inspections coordinated. You get a fully permitted, legal dwelling unit ready for move-in or rental.

Why Choose Gadget Construction

DBI Permit Specialists

We've navigated SF's ADU permit process dozens of times. We know what DBI wants and how to deliver it without delays.

Full Design-Build

Architecture, engineering, and construction managed by one team. Fewer handoffs mean fewer problems.

Value-Engineered

We design for maximum livability and property value without over-building. Smart investments, not vanity projects.

Fully Permitted & Legal

Every ADU we build is fully permitted with a Certificate of Occupancy. No gray areas, no surprises at tax time.

Our ADU Projects

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What Our Clients Say

“Gadget Construction transformed our 1940s Sunset District home into exactly what we envisioned. They handled everything — permits, inspections, the works. The crew showed up on time every single day and left the site spotless. We couldn't be happier with the result.”

Michael R.

Complete Remodel — Sunset District, SF

“After the last earthquake, we knew our foundation needed work. Gadget Construction came out the next day, explained everything in plain English, and gave us a detailed estimate. The work was done on schedule and on budget. We sleep better at night now.”

Sarah & David L.

Concrete Foundation — Bernal Heights, SF

“We wanted a deck that could handle San Francisco weather without constant maintenance. Gadget Construction recommended composite and walked us through every option. Six months in and it still looks brand new. Best investment we've made in this house.”

Jennifer K.

Composite Deck — Noe Valley, SF

Frequently Asked Questions

ADU costs in San Francisco typically range from $150,000 to $400,000+ depending on type, size, and finishes. Garage conversions start around $100,000–$200,000. Detached new-construction ADUs run $250,000–$400,000+ for a fully finished unit. Costs include design, engineering, permits, site work, construction, and finishes. We provide detailed estimates with line-item breakdowns.
The full timeline from design to move-in is typically 10–16 months. That breaks down roughly as: design and engineering (1–2 months), DBI permit review (2–4 months), and construction (4–8 months depending on type and size). Garage conversions are on the faster end. New detached construction takes longer. We give you a specific timeline at the estimate phase.
Under current California law, you can build a detached ADU up to 1,200 sq ft on most single-family lots in San Francisco, regardless of lot size or existing FAR. Junior ADUs (JADUs) can be up to 500 sq ft within your existing home. In many cases, you can build both a JADU and a detached ADU on the same lot. Setback and height requirements vary — we assess your specific lot during the feasibility visit.
Yes. ADUs in San Francisco can be rented out as long-term rentals. Current market rates for a 1-bedroom ADU in SF range from $2,000 to $3,500+/month depending on location, size, and finishes. Note: ADUs in SF are currently subject to rent control and just-cause eviction protections. We recommend consulting a property management professional for current rental regulations.
No. California law eliminates the parking requirement for ADUs in most cases, including when the ADU is within half a mile of public transit — which covers nearly all of San Francisco. Even if you convert your garage to an ADU, you are not required to replace the lost parking.
Yes. Studies show that a permitted ADU typically adds $200,000–$400,000+ to property value in the San Francisco market — often exceeding the construction cost. The rental income stream also improves your property's investment profile. A fully permitted, well-built ADU is one of the best ROI home improvements you can make in SF.

Thinking About an ADU?

Start with a free feasibility assessment. We'll evaluate your lot, walk you through your options, and tell you exactly what's possible — and what it will cost.

Or call (628) 233-3589 — talk to a real person, not a call center.
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