$2,250,000
155 12th Ave, San Mateo 94402
Size check
The listing's square footage against the county assessor's record and the permits on file.
The listing reports 762 sqft more than the county has on record, and no permit on file added floor area.
What can explain a difference
- Space built without a permit.
- Permitted work the assessor has not recorded yet.
- An ADU, a finished basement or a converted garage counted in one figure and not the other.
- Different measuring. Listing agents and the assessor often measure the same house differently.
AddressIntel AI Briefing
With high existing lot coverage and an already-updated interior, the optimal play is stealth density: primary + ADU + JADU to expand livable square footage. A full teardown is impractical due to FAR constraints, making a value-add remodel and accessory unit addition the most efficient path. The affluent local demographics and strong owner-occupancy support a high-end finished product.
Property Permit History
Recent Neighborhood Remodeling (San Mateo)
Parcel & Zoning Info
ADU Potential
Flag / irregular · ~101 ft frontage × 110 ft deep, a tucked-away rear unit is very private; access is typically via the pole driveway.
Screening heuristic based on lot size, existing coverage, lot orientation, and hazard overlays. CA ADU law is ministerial statewide; verify max size, setbacks, and JADU owner-occupancy with the local planning dept.
Redevelopment Potential
SB 79 preempts the limit these figures are measured against. This parcel sits within a half mile of a qualifying transit stop in a city that adopted the state standards, so state law overrides the local height and density caps and the governing envelope is a multifamily one, substantially larger than the city's single-family allowance. Read the score, class and headroom above as describing the municipal rule only, not this parcel's ceiling. Confirm the city's adopted SB 79 implementation before underwriting.
Existing home already uses most of the allowable floor area, little expansion headroom. The city’s single-family rule allows roughly 2,200 sqft of gross floor area on this lot.
Screening estimate comparing existing living area to the city's single-family floor-area limit, which SB 79 preempts on this parcel. FAR figure is a discretionary-review trigger, not a hard cap. Treat as approximate. Source: San Mateo Muni Code 27.18.060 (R1-B/C default; district unresolved) (as of 2026-08-24). Verify FAR, coverage, setbacks, and height with the local planning dept.
Hazard Snapshot
Flood Zone
Fire Severity
Liquefaction
Fault Zone
Not a substitute for a Natural Hazard Disclosure (NHD) report. Zones reflect available GIS data and may not cover all localities. Liquefaction and fault flags: modified from California Geological Survey, Web Service of Official Maps of Alquist-Priolo Earthquake Fault Zones and Web Service of Official Maps of Seismic Hazard Zones (2025).
Nearby Public Schools
Sunnybrae Elementary
San Mateo-Foster City
Borel Middle
San Mateo-Foster City
Aragon High
San Mateo Union High
School boundaries are subject to change. Nearest school distance does not guarantee enrollment eligibility. Check with the local district. Data provided by CDE.
Proprietary Intelligence
Market Heat Index
77/100
Based on recent sales velocity and local demand in 94402.
Flippability Score
60/100
Measures neighborhood renovation density vs. recent permits on this property.
Bidding War Prob.
59%
Likelihood of multiple offers based on local list-to-sale ratios and DOM.
Proforma ROI Calculator
Back-of-the-napkin deal analysis across development strategies.
SB 79 governs this parcel. It sits within a half mile of a qualifying transit stop in a city that adopted the state standards, so state law preempts the local height and density limits and the real ceiling here is a multifamily one, well above what the city's single-family rule allows. The figures below model a detached rebuild, which is not the play on this lot — we don't quote a return on it. Check the city's adopted SB 79 implementation before you underwrite.
Median of 12 recent single-family sales in San Mateo (94402): $1,534/sqft, plus 5% because new houses sold at a median 1.07x their comps across 239 real rebuilds. Sized within 25% of the 2,300 sqft build, because smaller houses sell for more per foot and pricing a rebuild off them overstates resale.
Commission, transfer tax and closing. Deducted from resale before profit, so the ROI below is net of the exit rather than gross.
Interest on the purchase price for the whole project plus half the build budget, since construction draws ramp up. The default is 7% over 33 months, the median purchase-to-sale time of 239 real Peninsula and South Bay rebuilds. Set the rate to 0 for a cash purchase, or use your own lender's terms.
Projected Profit
Warning: Project is mathematically underwater.
Recent Comparables (San Mateo 94402)
Sized to the modelled 2,300 sqft build: sales within 25% of it. Smaller houses sell for more per foot, so pricing a rebuild off them overstates resale.