San Mateo · City of San Mateo Community Development
San Mateo New Construction — Custom Homes & Small Multifamily
San Mateo custom homes, teardown rebuilds, and small multifamily infill are reviewed by the City of San Mateo Community Development Department. Peninsula permit cadence, FAR and design rules, electrification reach-code overlay on the 2025 California Energy Code, and SB9 / small-multifamily ordinance interpretation all shape the work.
CSLB #1098432 · License & insurance details on request
Quick Answer
If you are building or rebuilding in San Mateo, a written feasibility should confirm zoning, FAR allowance, design-review path, electrification scope, and (for multifamily) the City's SB9 implementation ordinance or qualifying R-zoning. Each path runs a different calendar.
Who this is for
- Owners teardown-rebuilding aging homes in Baywood, Aragon, San Mateo Park, or Hayward Park.
- Investors evaluating SB9 lot splits or small multifamily on qualifying R-zoned parcels.
- Buyers under contract on a San Mateo teardown lot needing pre-close feasibility.
- Owners building a new custom home on an intact parcel.
Who reviews new construction in San Mateo?
San Mateo is the City of San Mateo. Planning, plan-check, building permits, and inspections run through the City's Community Development Department. San Mateo County reviews unincorporated parcels — confirm jurisdiction on the Assessor record.
Single-family teardown rebuilds typically clear administrative review when designed inside the as-of-right envelope. Multifamily and SB9 projects route to the relevant ordinance and may trigger Planning Commission review for design.
What ground-up projects suit San Mateo
Teardown rebuilds
Removal of an aging single-family home and current-code ground-up replacement.
Custom homes on intact lots
Ground-up homes designed against the City's FAR and design rules.
SB9 duplex or lot split
Two-unit development or urban lot split on qualifying single-family parcels under the City's SB9 implementation ordinance.
Small multifamily (2–6 unit)
Infill duplex through fourplex on appropriately zoned parcels.
Local constraints that shape San Mateo budgets and schedules
San Mateo has adopted electrification policies that combine with the 2025 California Energy Code to push most new construction toward heat-pump space and water heating, induction-ready kitchens, and EV-ready service. Confirm current ordinance scope at permit filing.
FAR, height, setback, and design-review rules drive single-family envelope geometry. SB9 and small-multifamily ordinances have their own envelope and parking standards.
Many San Mateo parcels sit inside Seismic Hazard Zones for liquefaction; foundation design reflects soils data, not desktop assumption.
Cost factors specific to San Mateo
All-electric / heat-pump package and electric service upgrades.
Liquefaction-zone foundation reinforcement where soils require it.
Peninsula labor and material stack — comparable to neighboring Burlingame and Hillsborough for custom-home scope.
Small-multifamily MEP, sprinklers, and life-safety scope when above the single-family threshold.
Permit and timeline reality in San Mateo
Single-family administrative review projects clear faster than discretionary or multifamily projects. Realistic kickoff-to-permit envelopes are many months for single-family, longer for multifamily or SB9 with design iteration.
Construction of a San Mateo custom home commonly runs 12–18+ months; small-multifamily runs longer based on unit count and MEP scope.
Engineering you will actually need
Geotechnical report with attention to liquefaction-zone implications.
Drainage and erosion-control plan.
Title 24 Part 6 energy compliance under the 2025 code.
Structural and seismic design suited to parcel soils.
Fire/life-safety design (sprinklers, alarms) for multifamily where applicable.
Risks and bottlenecks unique to San Mateo
SB9 ordinance interpretation
Local implementation ordinances vary; a project that pencils statewide may not pencil under the local rule.
Liquefaction-zone foundations
Soils may push foundation cost above flat-lot intuition.
Service upgrades for all-electric
Panel and service upgrades can lag the permit.
Multifamily life-safety scope
Sprinklers and fire-rated assemblies push budget above single-family per-sq-ft.
Frequently asked questions
- Does the City of San Mateo or San Mateo County review my project?
- Depends on the parcel. In-city parcels go through the City's Community Development Department; unincorporated San Mateo County parcels go through the County's Planning & Building Department. Verify on the Assessor record.
- Is San Mateo all-electric?
- San Mateo's electrification policies combine with the 2025 California Energy Code to push most new construction toward all-electric. Confirm the current ordinance scope at permit filing.
- Can I do an SB9 lot split in San Mateo?
- Sometimes — SB9 applies to qualifying single-family parcels statewide, but the City's local implementation ordinance governs setbacks, parking exceptions, and other operational details. Feasibility against the parcel and the local ordinance is the only honest answer.
- Can I build a fourplex on my San Mateo parcel?
- Only if the parcel's zoning permits it or a state-law overlay applies. We screen multifamily feasibility against zoning and life-safety requirements in feasibility.
- How long does a San Mateo teardown rebuild take?
- Realistic envelope is many months from kickoff to permit issuance, then 12–18+ months of construction. We tighten in feasibility.
- Do I need geotech?
- Yes — Peninsula parcels need soils data and many sit inside Seismic Hazard Zones for liquefaction, which directly affects foundation design.
Official sources
- City of San Mateo — Community Development ↗
City of San Mateo
Authoritative permit, plan-check, and design review portal.
- San Mateo County — Planning & Building ↗
County of San Mateo
Jurisdiction for unincorporated parcels adjacent to the City.
- California Energy Commission — 2025 Energy Code ↗
California Energy Commission
Statewide Title 24 Part 6 baseline effective for permits filed on/after January 1, 2026.
- California Geological Survey — Seismic Hazard Zones ↗
California Department of Conservation
Alquist-Priolo and Seismic Hazard Zone maps for liquefaction and landslide.
- Bay Area Air Quality Management District — J-Number / Asbestos ↗
BAAQMD
Demolition notification and asbestos NESHAP requirements for Bay Area teardowns.
Related pages
- California New Construction hub →
Statewide overview of ground-up residential design-build.
- Bay Area New Construction →
Nine-county Bay Area permit patchwork and Peninsula context.
- Custom Homes →
Design-build framework for one-off custom home delivery.
- Teardown Rebuild →
Remodel vs rebuild analysis, demo permits, utility reconnects.
- Small Multifamily (2–6 unit) →
Infill duplex, triplex, and fourplex on R-zoned lots.
- New Construction Cost →
Honest 2026 cost ranges with named drivers.
- Permit Timeline →
Realistic plan-check, planning, and clearance windows.
- Design-Build Process →
How feasibility, design, permit, and build sit under one contract.
- Title 24 & CALGreen →
2025 California Energy Code, heat pumps, electric-ready requirements.
Plan a Peninsula new construction budget and permit path
We start every ground-up engagement with a written preconstruction feasibility review — before any contract is signed.
Plan a Peninsula new construction budget and permit path