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San Mateo County · Building on your lot

Affordable units in new housing (inclusionary) in San Mateo County

San Mateo County's own rules on affordable units in new housing (inclusionary), with the code text for every value.

Ask about affordable units in new housing (inclusionary) in San Mateo County See coverage

Each rule below links to the section of the San Mateo County Municipal Code it was read from, with the code text one click away (checked October 2026). General information, not legal advice.

What San Mateo County's code says

San Mateo County code What San Mateo County's code adds
How long units stay affordable
  • Affordable for 55 years.
    Applies: Affordable housing units provided under the county housing impact fee ordinance.
    § 5.154.160 · code text
    All affordable housing units shall remain affordable to the targeted income group for 55 years.
Exemptions
  • Exempt: residential projects subject to the cited zoning regulation sections, and accessory dwellings created under the zoning regulations.
    Applies: Exempt from the county housing impact fee.
    § 5.154.140 · code text
    The housing impact fee shall not apply to developers of residential development projects subject to Sections 7908 through 7918 of the San Mateo County Zoning Regulations (addressing inclusionary housing for projects consisting of five or more dwelling units) or any successor ordinance dealing with the same or similar subject; or accessory dwellings created under Chapter 22.5 of the Zoning Regulations.
  • Exempt: residential projects adding 1,500 square feet or less of net new square footage to existing dwellings.
    Applies: Exempt from the county housing impact fee.
    § 5.154.140 · code text
    The housing impact fee shall not apply to developers of residential development projects adding 1,500 square feet or less of net new square footage to existing dwellings.
  • Exempt: rebuilding after fire or calamity with materially the same square footage and use, if construction starts within 1 year.
    Applies: Exempt from the county housing impact fee.
    § 5.154.140 · code text
    Any structure proposed to repair or replace a building that was damaged or destroyed by fire or other calamity, so long as the square footage and use of the building remains materially the same, and construction of the replacement building begins within one year of the calamity resulting in the damage or destruction.

Who this affects

HomeownersContractorsDesigners

Frequently asked questions

Does San Mateo County require affordable units in new housing?

San Mateo County's code: Affordable for 55 years. (Affordable housing units provided under the county housing impact fee ordinance.) (§ 5.154.160); Exempt: residential projects subject to the cited zoning regulation sections, and accessory dwellings created under the zoning regulations. (Exempt from the county housing impact fee.) (§ 5.154.140).

General information, not legal advice.

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