In West Menlo Park, Your Address Doesn't Say Whose Rules Apply

"Honestly, we feel left out. We live here. We shop here. We eat here. But we can't vote here." That is how Kristen Kassai described her neighborhood to The Almanac in January. She lives in the West Menlo Triangle, about 60 homes between Alameda de las Pulgas and Santa Cruz Avenue. Her mail carries a Menlo Park address, but the land is governed by San Mateo County.

The voting issue gets the most attention. For a buyer, the bigger issue is who issues the permits. The question that decides whether a remodel, a new garden, or a tree removal goes the way you planned is which government's code covers the lot. In this part of West Menlo Park, that code can be stricter than the city's.

A 94025 address tells you where the mail goes, not who governs

The M-A Chronicle reported on October 1 that West Menlo Park shares a ZIP code with Menlo Park but is legally unincorporated San Mateo County. The county sheriff serves the area, the county maintains the roads, and residents cannot vote in Menlo Park city elections.

Permits follow the same line. San Mateo County's permit center handles unincorporated parcels, and its online portal tells applicants to confirm a parcel's zoning and jurisdiction before they apply. The City of Menlo Park publishes separate residential building-permit guidance for homes inside its boundary.

The listing, the ZIP code, and the name people use for the area don't show this boundary. It may only come up when an architect or arborist opens the parcel record. A buyer who budgets a project against Menlo Park's rules, on a lot governed by the county, has budgeted against the wrong rulebook.

The tree rules run the other way from what many people expect

Many people assume unincorporated land carries looser rules. A Triangle resident said as much in the same January Almanac report, telling the paper that heritage trees there are not protected the way they would be under city rules.

The county has since rewritten its rules. On October 22, 2024, San Mateo County adopted a Protected Tree Ordinance that replaced its older Significant Tree and Heritage Tree chapters. Under Section 8.400.060, any tree 12.1 inches in diameter or larger, measured 4.5 feet above natural grade, is protected, and a list of native species is protected at smaller sizes.

Menlo Park's thresholds, restated in the city's guidance published August 10, 2026, are 10 inches for native California oaks and 15 inches for every other species.

A 13-inch sycamore or a 13-inch madrone can be removed in the city without a heritage permit. Across the line in the county, both are protected. Native oaks are protected at 10 inches in both places. The county's guidance says removing a protected tree requires a permit, usually an arborist report, and in most cases a replacement tree.

Redwoods are the exception

Redwoods and Douglas firs reverse the pattern. The county protects them from 18 inches. The city protects them from 15. A 16-inch redwood near a planned addition needs a city permit inside Menlo Park and none under the county ordinance.

This is why a general sense that one jurisdiction is stricter can mislead you. The answer depends on the species and the trunk size, and on a mature lot it can change from one tree to the next. A site plan for an addition, a pool, or a detached studio has to be checked tree by tree against the code for that parcel.

The city adds its own requirements for construction. Menlo Park requires a permit to prune more than 25 percent of a heritage tree's foliage or roots within 12 months. It also requires an arborist report with a tree protection plan, from a city-approved consulting arborist, for construction near a heritage tree. Both systems treat the arborist as part of the project from the start.

Some county neighborhoods use an even lower bar. Emerald Lake Hills, Oak Knoll Manor, Palomar Park, and Devonshire protect any tree from 6 inches. West Menlo Park is not on that list.

Sidewalks, roads, and which agency responds

Trees are where an owner's plans most often run into the code. The jurisdiction line also affects the street.

County guidance makes the owner of property along a sidewalk responsible for maintaining it. The county may inspect or fix hazards, and work in the county right-of-way requires an encroachment permit. County Road Maintenance handles county-maintained roads in unincorporated areas. The county also publishes a map showing who is responsible for each street segment. In the city, Menlo Park Public Works maintains city streets.

The M-A Chronicle photographed Sharon Road without sidewalks along the street. Triangle resident Gregg Holzrichter told the paper that Harrison Way already has sidewalks and "feels indistinguishable from Menlo Park City." The county recently spent millions of dollars upgrading roads and pedestrian infrastructure along Alameda de las Pulgas. So the frontage you see can vary from one block to the next.

The county sheriff serves unincorporated areas. The Local Agency Formation Commission, San Mateo County's boundary agency, lists police among the City of Menlo Park's services. Resident Gregory Faris told the M-A Chronicle he would prefer city police because the nearest sheriff's station is in Redwood City.

Where the annexation stands in October 2026

Triangle residents applied to LAFCo in 2015. It is the longest known annexation attempt in San Mateo County history, and Councilmember Drew Combs has called the delay "embarrassing" for the city. Residents had already paid more than $10,000 in fees. On January 13, the City Council voted 3-1 to waive the remaining processing costs, which staff estimated at $60,000. Mayor Betsy Nash voted no, and Councilmember Cecelia Taylor was absent.

The city's project page still lists that vote as the latest milestone. It describes staff and LAFCo as working out roles, data needs, and costs. The January staff report lists the remaining steps:

1. A General Plan amendment and prezoning of the area to R1U.
2. Review under the California Environmental Quality Act.
3. Hearings before the Planning Commission and the City Council.
4. Negotiation with San Mateo County over how property tax revenue is split, and a resolution from the Board of Supervisors.
5. LAFCo's own processing, including a public meeting where protests can be heard.

The city says the work will move forward as staff time allows. Combs told the M-A Chronicle he hopes annexation "happens at some point in 2027." That is one councilmember's hope, not a city schedule. Anyone buying in the Triangle this fall should expect county rules to apply through any project starting in the next year, and possibly longer.

Annexation also covers only part of the area. The Triangle is about 14 acres. One reader commenting on The Almanac's January story said the unincorporated area extends well beyond the map the city released. Even if the Triangle joins the city, other nearby parcels may still be county land.

Before the offer, and before the design contract

These checks are quick, and they shape everything that follows:

• Confirm the jurisdiction. Check the parcel itself. A neighbor's house or the block's reputation won't tell you. The county portal explicitly asks applicants to verify zoning and jurisdiction first.
• Measure the trees that matter. Have an arborist measure every tree near a planned footprint at 4.5 feet and identify the species. The protection threshold depends on both.
• Look up the street. The county road-maintenance map shows who maintains the road in front of the house.
• Price the frontage. On county land, sidewalk upkeep falls to the adjacent owner, and right-of-way work needs an encroachment permit.
• Treat annexation as unsettled. Plan the project under the rules in force today. A future boundary change does not change today's rules.

A few questions that come up

If the Triangle is annexed, do county tree rules stop applying? Once a parcel becomes part of Menlo Park, city ordinances govern it. The January staff report says the area would first be prezoned R1U. The exact transition rules have not been published, so a project under way during the changeover should be confirmed with the city.

Is unincorporated land easier to build on? Not by default. For most non-native trees and several native species, the county's protection threshold is lower than the city's. For redwoods and Douglas firs, the city's is lower. Which code is easier depends on what grows on the lot.

Does a West Menlo Park address mean the home is outside the city? Not always. Some streets nearby are inside city limits and some are not. The parcel record is the reliable source.

West Menlo Park's mature trees are much of why people want to live there, and they are also where the county and city rules differ most. If you are weighing a home on either side of that line, or getting a West Menlo property ready for market, Scott Dancer can help you confirm the jurisdiction, line up the arborist, and set expectations before you make an offer or hire a designer. Let's Connect.