$1,198,000
221 N Delaware St, San Mateo 94401
Size check
The listing's square footage against the county assessor's record and the permits on file.
The listing and the county record agree within 10%.
- 2025-09-05 · Single Family (Alteration/Repair) - Alter
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
Given the low lot coverage and the 119-year age of the structure, the optimal play is an SB 9 lot split into multiple units to maximize the parcel's density. However, the liquefaction hazard zone acts as a development blocker that will require specialized structural engineering. The local demographics, characterized by lower median income and low owner-occupancy, skew this toward a high-yield rental hold or mid-market entry play.
Property Permit History
| Date | Project Type | Status | Valuation | Contractor |
|---|---|---|---|---|
| 2025-09-05 | Single Family (Alteration/Repair) - Alter | Finaled | $74,755 | Unknown |
Recent Neighborhood Remodeling (San Mateo)
Parcel & Zoning Info
ADU Potential
Flag / irregular · ~132 ft frontage × 148 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.
Small, older home using a low share of the allowable building envelope on a sizable lot, a scrape-and-rebuild or major-expansion play. The city’s single-family rule allows roughly 3,008 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
College Park Elementary
San Mateo-Foster City
Borel Middle
San Mateo-Foster City
The Bridge Academy
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
61/100
Based on recent sales velocity and local demand in 94401.
Flippability Score
78/100
Measures neighborhood renovation density vs. recent permits on this property.
Bidding War Prob.
32%
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 (94401): $897/sqft, plus 5% because new houses sold at a median 1.07x their comps across 239 real rebuilds. Sized within 25% of the 3,000 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 94401)
Sized to the modelled 3,000 sqft build: sales within 25% of it. Smaller houses sell for more per foot, so pricing a rebuild off them overstates resale.