A 2.0
Accessory dwelling units
A second unit in the ground floor, the garage or the back yard. State law has made the approval path faster and more predictable than almost anything else in this city.
Permit End to end 10–22 months
A 2.1 Schedule
How long this actually takes
Drawn at real proportion. If the bars before construction look long, that is the point of publishing them — it is the part of the calendar nobody warns you about.
Schedule Accessory dwelling units
| Phase | Duration | Timeline |
|---|---|---|
| Design CP | 8 weeks | |
| Entitlement | 6 weeks | |
| Permit CP | 14 weeks | |
| Construction CP | 22 weeks | |
| Closeout | 4 weeks |
- Design
- Entitlement
- Permit
- Construction
- Closeout
- On the critical path
About 12 months end to end against roughly 18 for an addition of similar size. Note that entitlement is not on the critical path here — that single difference is most of the six months, and it is a consequence of state law rather than of anything a builder does.
CP marks a phase on the critical path — one that moves the finish date if it slips. The critical path is marked with an outline and a label rather than a colour, so it is still readable in black and white and to a colour-blind reader. Every schedule on this site, side by side, is on the schedule page.
This is the one place where the schedule chart on this site gets shorter rather than longer, and it is worth understanding why.
California has spent several years passing legislation that limits what a city can require of an accessory dwelling unit and how long it can take to decide. The practical effect in San Francisco is that an ADU meeting the state standards follows a far more predictable path than an addition of the same size: less discretion, less exposure to a neighbour’s objection, and a statutory clock on the decision.
For an owner, that changes the arithmetic. An ADU and a rear addition can cost comparable money to build, and the ADU frequently finishes six months earlier because the entitlement bar collapses. If what you actually want is more space and you are flexible about its shape, that difference is worth knowing before an architect starts drawing.
The construction, though, is not easier. Putting a legal dwelling into a ground floor that was never one means ceiling height, light and ventilation, egress, fire separation, sound, waterproofing and frequently a structural upgrade — because the ground floor you are converting is often the soft storey holding up the rest of the house.
A ground floor needs a minimum finished ceiling height to be a legal dwelling. Plenty of San Francisco ground floors are two or three inches short. The remedy is to lower the floor, which means underpinning the foundation sequentially — a real structural project that can cost more than the rest of the unit. Measure it on the first visit; it decides whether the project exists.
Establish these first
- Where the unit goes
- Ground floor, garage, rear yard or a combination. Each has a different set of constraints and a different cost per square foot.
- Ceiling height and light
- The two things that most often make a ground floor unconvertible, and the two easiest to check before spending money on design.
- The structure above it
- A ground-floor conversion frequently removes wall that is holding the building up, which makes it a structural project as much as a space one.
- Utilities
- Whether the unit is separately metered, and where the sewer lateral, water service and electrical service actually run.
- What it is for
- Family, rental or resale. It changes the specification, and if it will be rented it changes what you are agreeing to as a landlord.
What you receive
Permit set, separate utility documentation, final sign-off, warranty package
Plus the things that are not documents: a schedule you can plan around, a written allowance for anything genuinely unknown, and a named person who answers the telephone. See how the money works.
A 2.2 Prices
What this scope costs
Planning ranges, wide on purpose. The full sheet with every scope on it, and a note on what moves a number to the top or the bottom of its range, is on the prices page.
| Item | Description | Unit | Range |
|---|---|---|---|
| B.10 | Ground-floor ADU, finished Full conversion including kitchen and bath | SF | $520–$900 |
| B.20 | Garage conversion ADU, finished Including replacing the garage door opening | SF | $560–$950 |
| B.30 | Detached rear-yard ADU New structure on its own foundation | SF | $700–$1,150 |
| B.40 | Underpinning to gain ceiling height Sequential underpinning and slab, per linear foot of wall | LF | $1,400–$3,200 |
| B.50 | Separate utility service Electrical, water and gas, separately metered | LS | $28,000–$95,000 |
| B.60 | Sewer lateral replacement Frequently required, frequently discovered late | LF | $320–$780 |
| B.70 | Fire and sound separation Assemblies between the unit and the rest of the building | SF | $38–$95 |
Units are SF square foot of the area being built, LF linear foot, CY cubic yard, SQ roofing square (100 SF), EA each, LS lump sum. A square-foot rate is for the area of new or renovated space, not for the whole house.
Prices are USD planning ranges for San Francisco residential work, exclude design and engineering fees, city permit and impact fees, geotechnical and hazardous-materials assessment, furnishings and any applicable tax, and assume normal access and no undisclosed conditions. Durations are planning ranges that assume no discretionary review and one round of plan-check corrections. They are published so an owner can plan before spending money on drawings. They are planning ranges, not a bid. Reviewed October 2026. A price and a schedule for your project come from a written proposal against a defined scope. See the disclaimer.
A 2.3 Questions
Questions about this scope
Specific to this kind of project. The general ones — contracts, deposits, allowances, change orders, insurance, who does what — are on the FAQ page.
Is an ADU really faster than an addition?
On the approval side, usually and substantially — and the schedule charts on this page and on the additions page are drawn to show exactly that. State law limits what the city can require and puts a clock on the decision, which removes most of the discretion an addition is exposed to. On the construction side it is not faster at all; a ground-floor conversion is a demanding build. The saving is in the calendar before demolition, not in the build.
Do I have to rent it out?
No. An ADU can be for family, for yourself, or left empty. What changes if you do rent it is that you become a landlord in a city with strong tenant protections, and that is a decision worth taking advice on before construction rather than after. We are builders and will say so rather than advising you on it.
Will an ADU pay for itself?
That is a question for you, your accountant and the rental market rather than for your builder, and anybody who answers it confidently on a first call is selling you something. What we can do is give you a real construction number and a real schedule so that the calculation you make is made on true inputs. The most common way this goes wrong is an owner budgeting from a per-square-foot figure they read somewhere and discovering the underpinning six months in.
Can I convert my garage and still park?
Usually not both, in the same footprint. San Francisco no longer requires most residential buildings to provide parking, which is what makes garage conversions possible at all, but the space is the space. Where the lot allows it there is sometimes room to keep a pad outside; frequently there is not, and that is a real trade-off to weigh before you commit.
A 0.0 The other scopes
The other four
Each accented by the phase that dominates its schedule, which is where you should expect the surprises.
Adding to a San Francisco house — out the back, up a storey, or down into the ground floor. The construction is ordinary; the entitlement almost never is.
- You receive
- Permit set, structural calculations, final inspection sign-off, as-builts
Soft-storey retrofit, foundation replacement, shear walls and moment frames on buildings put up before anybody wrote the rules they are now judged by.
- You receive
- Engineer’s calculations, permit set, special inspection records, final sign-off
Renovating a small apartment building around the people who live in it. The sequence is set by habitability and access rules, not by what is convenient.
- You receive
- Permit set, tenant notices and schedules, inspection records, as-builts
A house on an infill lot, or a rebuild behind a facade the city will not let you remove. The longest schedules on this site, and the ones where entitlement dominates most.
- You receive
- Full permit set, structural and energy documentation, certificate of final completion
Tell us about the building
What it is, roughly when it was built, what you want to do to it, and whether anybody is living in it. On a first call we can usually tell you which approval path you are on, what the realistic end-to-end schedule looks like, and what about your project is most likely to go sideways.
Trico Construction, LLC · 981 Howard St, San Francisco, CA 94103