Before You Sign
The same project, in 16 cities, is 16 different projects
People assume the local rules are roughly the same across the valley and vary at the edges. They are not. Here is the specific thing that catches people out in each of the sixteen cities we work in.
Every city here is its own jurisdiction, and the difference is not a matter of degree. In Mountain View the City states it deliberately has no discretionary design review for single-family homes. Twelve minutes down the road in Cupertino, adding a second storey needs a discretionary permit, a two-week public comment period and a rendering posted on your lawn. In Monte Sereno an addition that pushes the house past 3,600 square feet can trigger fire sprinklers throughout the existing home. In Atherton a tree permit has to issue before the building permit can. None of that is visible from a floor plan, and all of it is knowable before you pay anyone to draw one.
The one thing that surprises people, city by city
Each row links to that city's page, where the detail and the source live. This is not the whole rulebook for anywhere — it is the item we most often have to explain to someone who assumed their project would work the same way it would one town over.
| City | The thing that catches people out | What it costs you |
|---|---|---|
| Atherton | A heritage tree removal permit must be approved and issued before the building permit can issue. Anything from your gate to the street is a separate encroachment permit. | A gate in the schedule, plus an arborist report at your expense |
| Campbell | Second-storey additions go to a Site and Architectural Review Permit hearing — the City's own notices show additions in the 500 to 600 sq ft range being heard. | A public hearing on a job you thought was routine |
| Cupertino | Going up needs a discretionary Two-Story Permit, with a two-week public comment period and a City-approved rendering posted on site. Single-Story Overlay neighbourhoods cannot go up at all. | Weeks of process, or a second storey that is simply unavailable |
| Gilroy | Plans go out for a 30-day review by Planning, Building, Engineering and Fire at once, and the City says revisions are typically necessary. | Budget for a round trip, not one clean pass |
| Los Altos Hills | Slope is a multiplier on how much house you are allowed. Floor area and development area come from published formulas. Garages count. Double-height space counts twice. | A steeper lot is permitted less building, not just harder building |
| Los Gatos | In the Hillside Area, whether the house is visible from an established viewing area decides who approves it — and drops the height limit to 18 ft above grade for ridgeline and visible homes. | Visibility changes both your approver and your design |
| Milpitas | CALGreen construction waste recycling applies to residential with no dollar threshold — any addition that adds conditioned space. Two-part filing, two departments. | Part I gates the permit; Part II gates the final inspection |
| Monte Sereno | An addition that takes the house past 3,600 sq ft can require fire sprinklers in the whole existing home. Narrow exception for a one-time addition under 1,000 sq ft. | The most expensive hundred square feet you will ever add |
| Mountain View | The City states it has no discretionary design review and no neighbour noticing for single-family homes, deliberately. Meet the standards and Planning is largely not involved. | The friendliest process on this list — but the numbers must be exact |
| Palo Alto | By its own description the only city in California that owns and operates a full suite of municipal utilities — electric, gas, water, wastewater and fibre. | One relationship instead of three, and no alternative provider |
| Portola Valley | The Town regulates more of a residential project than anywhere else we work: a 50 Percent Rule, a Story Pole Policy, creek setbacks, grading permits, each its own published document. | Story poles are a real line item and a real wait |
| San Jose | PG&E now requires an ADU to carry its own utility meter — and the City states plainly that this is the utility's policy, not the City's. | A separate electrical service, in the number from day one |
| Santa Clara | Not PG&E. Silicon Valley Power is a department of the City itself, so every piece of PG&E advice you have read is the wrong answer here. | A different utility process on a different timeline |
| Saratoga | Arborist review is triggered within five feet of a protected tree's dripline — including your neighbour's trees — and parking vehicles or storing materials in a root zone counts as construction. | Your site logistics get designed by the trees |
| Sunnyvale | An ADU larger than 800 sq ft needs a Miscellaneous Plan Permit before the building permit. Replacing kitchen cabinets needs a permit; refacing them does not. | Twenty extra square feet can cost you an extra application |
| Woodside | The Woodside Fire Protection District runs its own review and issues its own permit, roughly 14 days, alongside the Town's. Its defensible space ordinance applies in all zones, not only Very High. | A second permit on a second clock, and Chapter 7A materials |
Four patterns worth understanding before you pick a designer
1. Going up is a public process in more places than going out
A second storey is where discretionary review concentrates. Cupertino requires a Two-Story Permit with a comment period. Campbell hears second-storey additions at Planning Commission at sizes most people would call small. Los Gatos requires Architecture and Site approval for hillside work. Monte Sereno runs a Site Development Permit through its Site and Architecture Commission with story poles.
The practical consequence: on a flat lot with a usable rear yard, a detached ADU or a single-storey addition often reaches the same square footage without entering any of that. That is a real trade worth pricing both ways before anyone commits to a design. It is also why we ask what you actually need the space for before we ask how big you want it.
2. Trees decide schedules, and sometimes site logistics
In Atherton the tree permit gates the building permit outright. In Saratoga the trigger is construction within five feet of a protected dripline, your neighbour's trees included, and the City counts parking and material storage as construction — so the trees can remove the obvious spot for the dumpster and the crew trucks. Los Gatos runs canopy-based replacement with in-lieu payment. Palo Alto's older neighbourhoods carry protections that decide where a foundation is allowed to sit.
In all four, the tree survey is an input to design, not a document you produce afterwards. A design drawn first and surveyed second gets redrawn.
3. “PG&E requires it” is not a statewide answer
Santa Clara is Silicon Valley Power. Palo Alto runs its own electric, gas, water and wastewater. Most of the rest of our area is PG&E. On an ADU or a service upgrade that is a genuinely different process with a different queue, and almost everything written online about ADU metering silently assumes PG&E territory.
There is a related trap worth knowing. State law limits what a city, a special district or a water corporation can charge you for an ADU utility connection — but an electrical corporation like PG&E is on none of those lists, which is exactly why San Jose says the metering policy is not its call.
4. The quiet thresholds are the expensive ones
Three numbers on this page can move a budget by more than any finish decision in the project, and none of them are visible on a floor plan:
- Monte Sereno, 3,600 sq ft. Cross it with an addition and you may be sprinklering the entire existing house.
- Sunnyvale, 800 sq ft. An ADU above it needs an extra application before the building permit.
- Milpitas, no threshold at all. Any addition adding conditioned space triggers the full construction waste diversion process.
Each one turns on a number you control while the project is still on paper. That is the argument for establishing them first, and it is most of what a builder is doing in the weeks before anything gets built.
We ask which city before we ask anything about the project, because it changes what the first conversation should even be about. If you already have plans, we price and build them — and we check them against the local rules before we quote, rather than discovering the problem at plan check.
How to check your own city properly
Start at the city's own website, not a contractor's
Including ours. This page is a summary written on one day, and cities amend ordinances. The city's page is the version that governs, which is why every row above links to a page where we name our source.
Ask the planning counter two questions
“Does what I am describing need any discretionary approval?” and “What else besides the building permit will I need?” The second one is where the fire district permit, the tree permit and the encroachment permit surface.
Establish the numbers before design, not after
Net site area, floor area allowance, any slope adjustment, and the thresholds that apply to your scope. Several cities publish worksheets for exactly this and take pre-application appointments.
Ask any bidder which city rules they have priced for
A number produced without knowing whether your project needs a hearing, a second permit or a sprinkler system is not a price. It is a guess that will be corrected later, at your expense.
Common questions
Is this the complete set of rules for these cities?
Why do the rules vary this much between neighbouring cities?
Does this change what a project costs, or just how long it takes?
We already have plans drawn. Is it too late?
Do you work outside these sixteen cities?
Where to go next
Written by the team at Elusive Construction, a licensed California general contractor (B #1112902) building in Santa Clara and San Mateo counties. General information about how residential construction works — not legal advice. For your specific contract, talk to an attorney.
Also Worth Reading
The rest of what we publish
Cost guides
What an ADU, an addition, a kitchen or a whole house actually costs here, and what moves each number.
Our own projects
Two jobs written up start to finish, including what we found once the walls were open.
Paying for it
Renovation lenders we work with. We take no referral fee, and we never quote you a rate.
Where we build
Sixteen cities across two counties, and what genuinely changes at each city line.
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