Millbrae Neighborhoods by Their Lots: Lot Sizes, Flood Zones and Fire Zones

San Mateo County’s public parcel layer gives an outline and a property use code for every parcel. We took the 5,369 parcels with the county’s single-family use code, 1,500 square feet or more, inside our five Millbrae neighborhood guides, measured each lot from its outline, checked its center against FEMA’s flood map and checked each lot against CAL FIRE’s fire hazard severity zone maps. The layer has no year built, house size or city-limit line, so this post covers our five guides rather than the city as a whole. Parcel outlines downloaded October 2026; the county’s use codes were last updated in June 2020. There are no addresses or owner details here.

The short answer

• Across our five Millbrae guides, the median single-family lot is 6,130 sq ft.
• Largest lots: Mills Estates, Millbrae side (9,090 sq ft) and Glenview Highlands & Millbrae Meadows (6,160 sq ft).
• Smallest: Downtown, Marina Vista & Bayside Manor (4,990 sq ft) and Green Hills, Lomita Hills & Capuchino (5,420 sq ft).
• Flood zones: 177 of the 5,369 lots (3%) have their parcel center in a FEMA high-risk flood zone (121 in AE, 53 in AH and 3 in A); all of them in Downtown, Marina Vista & Bayside Manor (174) and Green Hills, Lomita Hills & Capuchino (3).
• Fire zones: 2,382 lots (44%) are at least partly in a CAL FIRE fire hazard severity zone: 1,010 Very High, 695 High and 677 Moderate. The most are in Glenview Highlands & Millbrae Meadows (1,252) and Mills Estates, Millbrae side (539).

Neighborhood by neighborhood

Largest median lot first. “Single-family lots” counts parcels with the county’s single-family use code whose center falls inside each guide’s outline; no lot falls in two guides. Each name opens its guide.

What stands out

• Mills Estates (Millbrae side) has the biggest lots: a median of 9,090 sq ft, about 1.5 times the median across our guides.
• Most fire-zone lots are in Glenview Highlands & Millbrae Meadows: 1,252 of its 1,254 lots (over 99%) touch one, 615 of them Very High.
• Most flood-zone lots are in Downtown, Marina Vista & Bayside Manor: 174 of its 544 lots (32%), in zones AE and AH.

Flood zones, neighborhood by neighborhood

Single-family lots in FEMA high-risk zones inside each guide’s outline, the share of the guide’s lots they make up, and the zones; most first. The other three guides have none.

What the flood zones mean

• Zone A: a 1%-a-year chance of flooding, where FEMA hasn’t set a base flood elevation.
• Zone AE: the same 1%-a-year risk, with a base flood elevation set.
• Zone AH: shallow ponding, usually 1 to 3 feet deep, with the same 1%-a-year risk and a base flood elevation.
• Zone X: moderate to minimal risk, outside the 1%-a-year floodplain.
• Insurance: if the house itself is in an A or V zone, lenders on federally backed mortgages require flood insurance; a flood zone determination for the address settles it. In zone X it’s optional.

Fire hazard zones, neighborhood by neighborhood

CAL FIRE maps how severe the wildfire hazard is across California, in three classes: Moderate, High and Very High. Single-family lots inside each guide’s outline, by the highest zone that touches any part of the lot; most severe first. The other guide has none in any zone.

What the fire zones mean

• Hazard, not risk. CAL FIRE’s Office of the State Fire Marshal says the maps describe hazard: the physical conditions, like vegetation, terrain, fire history, embers and typical fire weather, over 30 to 50 years. They don’t count home hardening, defensible space or fuel reduction, which change the risk to a particular home (OSFM).
• Two kinds of map. Inside city limits (Local Responsibility Areas) we used CAL FIRE’s 2025 map; where the state is responsible for wildfire protection (State Responsibility Areas), its State Responsibility Area map. Land outside the three classes is shown as non-wildland or unzoned (OSFM).
• What a zone can bring. Depending on the zone and the kind of area, stricter building standards for new construction and additions, defensible-space rules, and a line on the seller’s natural hazard disclosure. The city’s building department can say which apply.

Reading it right

• A use code isn’t a zoning district. We counted parcels the county codes as single-family residences, 1,500 square feet or more; the codes date from June 2020, so a few newer houses may be missing or coded otherwise, and townhomes and condos aren’t counted.
• Lot sizes are measured from the county’s parcel outlines, so they can differ from a survey by a few percent.
• We checked the center of each lot against FEMA’s National Flood Hazard Layer. A lot can straddle two zones, and maps change, so check the current FEMA map for the exact address.
• The flood zone covers the land, not the house. A house can sit above the base flood elevation even in a high-risk zone. An elevation certificate settles it and can lower the insurance price.
• The fire zone describes the land around a house, not how the house is built or how the lot is kept. CAL FIRE’s zone viewer shows any parcel, and a seller’s natural hazard disclosure report states the zones for that property.
• A median isn’t a verdict. It describes the lots, not which neighborhood is right for you.

Go deeper

Millbrae Housing Market by the Numbers covers prices and bidding, Millbrae Neighborhoods Ranked by Price per Square Foot compares the neighborhoods on price, and The Most Expensive Streets in San Bruno & Millbrae goes street by street. Flood & Fire Zones by Neighborhood compares every guide we write, and the Millbrae city guide links every neighborhood guide.

The Millbrae data series: housing market by the numbers · neighborhoods ranked by price per sq ft · where homes sell over asking · ten years of prices by neighborhood · condos and townhomes · house prices by bedrooms · houses under $2M · houses at $2.8M and up · the best month to sell · the most expensive streets (with San Bruno)

Buying, selling or rebuilding in a flood or fire zone?

A Property Nerd can pull the zoning, the lot, the flood and fire zones, any elevation certificate and the recent sales on your street before you write an offer, set a price or plan a rebuild. Call (408) 373-1660 or (650) 383-8606, or book a strategy call. Commissions are negotiable, and we offer bundled services, so ask us what’s included.