San Marcos · Building on your lot
Building on your lot in San Marcos
San Marcos sets its own limits on accessory structures and home businesses, and has a separate chapter on walls and fences. Accessory structure limits do not apply to accessory dwelling units.
Key points
- Accessory height: Accessory structures are limited to 1 story and 15 feet, and may be no higher than the main home (city rule).
- Home businesses: A home business may use at most 200 square feet unless the Director approves more; only residents may work there.
- Fences: The city has a separate chapter on walls and fences.
Each rule below is marked San Marcos code or CA state law and links to the section it comes from (checked October 2026). General information, not legal advice.
Sheds, garages and other accessory structures
San Marcos code Accessory structures are limited to 1 story and 15 feet, and may be no higher than the main home (city rule).
All 5 San Marcos rules on sheds, garages and other accessory structures, with the code text →
Running a business from home
San Marcos code A home business may use at most 200 square feet unless the Director approves more; only residents may work there.
All 4 San Marcos rules on running a business from home, with the code text →
Lot splits under SB 9
San Marcos code 2 parcels of about equal area; neither may be smaller than 40% of the original lot. Each new parcel must be at least 1,200 square feet.
All 8 San Marcos rules on lot splits under SB 9, with the code text →
Solar panels and EV chargers
San Marcos code Apply in person, by mail or online; the building official approves administratively and issues permits when the checklist is met. Panels may not be taller than the maximum legal building height.
All 5 San Marcos rules on solar panels and EV chargers, with the code text →
Swimming pools
San Marcos code No horizontal openings larger than 5 inches. The barrier must prevent ladder-like climbing access.
All 4 San Marcos rules on swimming pools, with the code text →
Building in a flood zone
| Floodplain permit |
|
|---|---|
| Building in a floodway |
|
| Height of the lowest floor |
|
Grading and erosion control
| Grading without a permit |
|
|---|
Building on a hillside
San Marcos code A preliminary soils report from a certified engineer is required. Grading may cover no more than 25% of the lot area.
All 11 San Marcos rules on building on a hillside, with the code text →
Family child care homes
| Zoning | A small or large family child care home is a residential use and a use by right under all local ordinances, including zoning |
|---|---|
| Business license or fee | A city or county may not charge a business license, fee or tax to run a family child care home |
| Local rules | Local limits on height, setbacks, lot size, health and safety must be the same as for every other home in the same zone |
| Small home | Up to eight children, counting the provider's own children under 10 who live there |
| Large home | 7 to 14 children, counting the provider's own children under 10 who live there |
Affordable units in new housing (inclusionary)
San Marcos code Affordable for a minimum of 55 years. Affordable for a minimum of 55 years.
All 15 San Marcos rules on affordable units in new housing (inclusionary), with the code text →
Parking spaces required for homes
San Marcos code 1 space must be covered 1 space must be covered
All 18 San Marcos rules on parking spaces required for homes, with the code text →
Signs on homes
| Signs that need no permit |
|
|---|
Trash and recycling carts
San Marcos code Required; exemption needs proof of County facility use: at least 52 receipts a year, 7 days or less apart Not left out after 6:00 p.m. on the day of collection
All 5 San Marcos rules on trash and recycling carts, with the code text →
Other San Marcos rules on this
San Marcos's code also has these chapters. We have not summarized their values on this page yet; read them in the library.
- Walls and fences (Ch. 20.335)
- Animal keeping permits and standards (§ 20.415.020)
- Overnight parking of RVs on public streets (§ 12.20.170) — on public streets
- Using or storing a trailer coach or RV (§ 16.08.010)
- Noise rules (Ch. 10.24)
- Public facilities fees on new construction (§ 17.44.060)
Who this affects
Frequently asked questions
How tall can a fence be in San Marcos?
The city has a separate chapter on walls and fences. San Marcos also has a related rule: Walls and fences (Ch. 20.335).
What are the rules for building in a San Marcos flood zone?
San Marcos's code: You need a permit before any construction or development, including manufactured homes, in a special flood hazard area. (Special flood hazard areas.) (§ 20.255.100); The lowest floor must be 2 feet above the base flood elevation. (New or substantially improved homes in Zones AE, AH and A1-30.) (§ 20.255.110).
What are the grading rules in San Marcos?
San Marcos's code: Grading of 200 cubic yards or less per lot needs no permit if cuts and fills stay within 4 feet. (New slopes no steeper than 2:1; no fill on slopes over 5:1; no drainage change; under 5,000 square feet new paving; floodplain grading needs permits.) (§ 17.32.045).
Can I run a family child care home in San Marcos?
California law sets this for every city, including San Marcos: Zoning: A small or large family child care home is a residential use and a use by right under all local ordinances, including zoning (Health & Safety Code § 1597.45(a)); Business license or fee: A city or county may not charge a business license, fee or tax to run a family child care home (Health & Safety Code § 1597.45(b)); Local rules: Local limits on height, setbacks, lot size, health and safety must be the same as for every other home in the same zone (Health & Safety Code § 1597.45(e)); Small home: Up to eight children, counting the provider's own children under 10 who live there (Health & Safety Code § 1596.78(c)); Large home: 7 to 14 children, counting the provider's own children under 10 who live there (Health & Safety Code § 1596.78(b)).
What signs may I put up at my home in San Marcos?
San Marcos's code: No permit for warning and notice signs ("no trespassing") if total area is 4 square feet or less per parcel (§ 20.320.080).
General information, not legal advice.
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