San Carlos CA Real Estate & Homes For Sale

Permits, ADUs and remodels in San Carlos

The City of San Carlos reviews single-family work at staff level through a Single Family Compliance Review. It covers first-floor additions, second-floor additions and new homes (City of San Carlos, Single Family Compliance Review application). The application lays out what that review involves:

• Development and design standards. Plans are checked against the RS-district development standards (SCMC 18.04.030) and the Objective Design Standards for RS districts (18.04.040). The design standards cover entries, garages, massing, roofs, windows, materials and lighting. For example, no façade may run 25 feet or more without an articulating feature.
• Neighborhood notification is required for projects creating 3,000 square feet or more of floor area, with an added fee.
• Protected trees. An arborist report may be required for tree removal. A Tree Protection Plan by an ISA Certified Arborist is required for work within a protected tree’s protection zone.
• Creeks. Lots along creeks may fall in the Stream Development and Maintenance (SDM) overlay (Chapter 18.14).

ADUs and junior ADUs that meet state standards are approved ministerially, within 60 days of a complete application (HCD). Before you rely on a second unit, check its permit history; see San Carlos improvement records and buying a home with an ADU. Review periods apply to qualifying complete applications and the applicable state pathway, with statutory exceptions; they do not guarantee that a proposed unit is feasible or that a building permit will be issued. Confirm the current requirements with the permit agency and HCD.

Costs to plan for when buying in San Carlos

San Mateo County’s documentary transfer tax is $1.10 per $1,000 of value (San Mateo County Clerk-Recorder). Confirm the actual County/City transfer charges and any credited statutory City share with escrow; do not add every local share to the County rate. A large addition or new home also carries soft costs: arborist reports, neighborhood-notification fees and, on hillside lots, slope calculations for the plans. For yearly costs, see San Mateo County property tax and San Carlos association and assessment costs.

Luxury homes and estates in San Carlos

In San Carlos, the clearest planning marker for a high-end property is the Hillside (H) Overlay District (Chapter 18.12). It applies to every lot with an average slope of 20% or more, calculated with the formula in SCMC 18.03.070 (Compliance Review application). The overlay’s standards shape what a view lot can hold:

• The baseline natural-state standard is 35%, with the exceptions inSCMC 18.12.050(C).
• Buildings can be no taller than 35 feet, measured from the lowest finished grade.
• The downhill face can be no taller than 20 feet.
• The table limits underfloor height to 6 feet and retaining-wall height in front and rearsetbacks to 6 feet; other walls have separate height/terracing provisions.
• Driveways can be no steeper than 18%.

So a large hillside lot may allow less house or yard than its acreage suggests. Compare the existing home with these limits before you pay for expansion potential.

The due diligence that matters most on a high-value San Carlos home:

• Permits for existing work. Match decks, retaining walls and additions to permit history.
• Trees. Protected trees can limit where you can build.
• Fire zone and insurance. Check the address on the state fire hazard map. See insuring a high-value home and the FAIR Plan guide.
• Airport. Homes near San Carlos Airport need both a noise check and a land-use compatibility check.

Ask Diamond Real Estate Group which permitted private-marketing options fit your property, goals and the applicable MLS rules. Availability of any particular listing is not guaranteed. Related reading: private sales. Nearby, see Belmont, Redwood City and San Mateo County estate-town design review, plus San Mateo County luxury homes.

San Carlos real estate: questions people ask

Does the hillside overlay apply to my San Carlos lot?

It applies if the lot’s average slope is 20% or more, calculated with the formula in SCMC 18.03.070 from contour intervals, contour length and parcel area. A designer or surveyor runs the calculation for the plans. If it applies, the overlay’s limits on natural state, height, downhill face, retaining walls and driveway slope go on the plan set.

Do I need design review to add a second story in San Carlos?

Yes, in the sense that second-floor additions go through the city’s staff-level Single Family Compliance Review. Plans are checked against the RS development standards and objective design standards. The February 2026City application requires neighborhood notification for a new home or addition creating a total of 3,000 square feet or more of floor area; the threshold is not 3,000 square feet of new addition alone. Ask the planning division about current fees and timelines.

Does San Carlos have a city transfer tax?

Confirm any applicable County/City charge and statutory credit with escrow. A San Carlos sale normally pays only the county documentary transfer tax of $1.10 per $1,000. Confirm with escrow, and remember that who pays is negotiable in the purchase contract.

Transfer-tax calculations depend on the actual taxable consideration/value, statutory thresholds, fractional-unit rounding and exemptions. Ask escrow for an itemized calculation for the specific transfer; who pays is generally negotiable.

Sources for this section

1. City of San Carlos, Single Family Compliance Review Application (RS standards, Objective Design Standards, Hillside Overlay Table 3, tree protection): https://cms3.revize.com/revize/sancarlos/Single%20Family%20Compliance%20Review%20Application%20Fillable.pdf
2. California HCD, Accessory Dwelling Units: https://www.hcd.ca.gov/building-standards/adu
3. San Mateo County Clerk-Recorder, Documentary Transfer Tax: https://smcacre.gov/county-clerk-recorder/documentary-transfer-tax
4. Office of the State Fire Marshal, Fire Hazard Severity Zones: https://osfm.fire.ca.gov/what-we-do/community-wildfire-preparedness-and-mitigation/fire-hazard-severity-zones