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.

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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 What San Marcos's code adds
Maximum height	No more than 1 story and 15 feet at the roof peak. Also no higher than the main home. Does not apply to ADUs. § 20.410.040 · code text Height of the accessory structure(s) shall be one (1) story maximum, up to a maximum of fifteen (15) feet at peak of roof, and shall not exceed the height of the primary dwelling unit.
Size or lot coverage	No more than 40% of the main home's living area or 800 square feet, whichever is less. Applies: All fully enclosed accessory structures with an existing single-family home, not counting ADUs. § 20.410.040 · code text The maximum allowable gross floor area for all completely enclosed accessory structures in conjunction with an existing single-family residence, excluding ADUs, shall be equal to forty percent (40%) of the living area of the primary dwelling unit, or eight hundred (800) square feet of gross floor area, whichever is less.
Side and rear setback	At least 5 feet from the rear property line. Applies: Rear property line setback. § 20.410.040 · code text Rear property line setback: minimum five (5)-foot setback required. At least 5 feet from the interior property line. Applies: Accessory structures behind the main building, in the rear yard area. § 20.410.040 · code text If located behind the primary building, minimum of five (5)-foot setback to interior property line shall be permitted in the rear yard area.
Distance from the house	At least 10 feet from the main home or any other accessory structure. Applies: Detached accessory structures. § 20.410.040 · code text If detached, a minimum of ten (10) feet separation from the primary dwelling unit or any other accessory structure.

Running a business from home

San Marcos code What San Marcos's code adds
Space used	No more than 200 square feet of floor space. Applies: Floor space inside the home used for the business, unless the Director approves otherwise. § 20.400.100 · code text A maximum of two hundred (200) square feet of floor space within the dwelling shall be devoted to the home occupation business use, unless otherwise approved by the Director.
Employees	No one else may be employed at the residence. Applies: Residents of the home must conduct the business. § 20.400.100 · code text The home occupation business use shall be conducted by residents of the dwelling; no other person shall be employed at the residence.
Permit	A business license is required. Applies: Before a home business starts. All standards must be met before the license is issued. § 20.400.100 · code text Prior to establishment of a home occupation, the resident/business owner shall be required to obtain a business license in conformance with the requirements of Chapter 3.08 of this Code.
Businesses not allowed	No display or storage of goods, wares, merchandise, or stock in trade on the premises § 20.400.100 · code text No display or storage of goods, wares, merchandise, or stock in trade shall be maintained on the premises.

Lot splits under SB 9

San Marcos code What San Marcos's code adds
How the lot may be divided	2 parcels of about equal area; neither may be smaller than 40% of the original lot. Applies: Applies to urban lot splits in a single-family residential zone. § 19.44.050 · code text Both newly create parcels shall be of approximately equal lot area, which for purposes of this paragraph shall mean that one parcel shall not be smaller than 40 percent of the lot area of the original parcel proposed for subdivision.
Minimum new lot size	Each new parcel must be at least 1,200 square feet. § 19.44.050 · code text Both newly created parcels shall be no smaller than 1,200 square feet.
Standards	Units may be at most 16 feet tall and 1 story. Applies: Applies to units built on an urban lot split, measured from the lower of existing or finished grade. § 19.44.050 · code text Units constructed on an urban lot split subdivision approved pursuant to this chapter shall not exceed sixteen feet (16') in height and one story, measured from preexisting grade or finished grade, whichever is lower, to the highest point of the roof. Each unit must have vehicle access to and from the public right-of-way. Applies: Applies to each unit on a parcel created by an urban lot split. § 19.44.050 · code text Each unit located on a parcel created pursuant to this chapter shall have vehicular ingress and egress to the public right-of-way. Only residential uses are allowed. Applies: Applies to parcels created by an urban lot split. § 19.44.050 · code text The uses allowed on a parcel created pursuant to this chapter shall be limited to residential uses. No more than 2 lots, and no more than 4 units in total across the 2 lots. Applies: Applies to an urban lot split map. § 19.44.110 · code text The subdivision proposed creation of more than two lots or more than four units total among the two lots.
Owner occupancy	A recorded affidavit to live in one unit as the main home for at least 3 years from approval. Applies: Applies to urban lot split applicants, except community land trusts and qualified nonprofit corporations. § 19.44.030 · code text An applicant for an urban lot split subdivision shall sign and submit with the application an affidavit stating that the applicant intends to occupy one of the housing units as their principal residence for a minimum of three (3) years from the date of the approval of the urban lot split. No owner-occupancy affidavit is required. Applies: Applies when the applicant is a community land trust or a qualified nonprofit corporation. § 19.44.030 · code text An affidavit shall not be required of an applicant that is either a "community land trust" or a "qualified nonprofit corporation" as defined in the Revenue and Taxation Code.

Solar panels and EV chargers

San Marcos code What San Marcos's code adds
EV charger permit	Apply in person, by mail or online; the building official approves administratively and issues permits when the checklist is met. Applies: Applies to complete applications with supporting documents that meet the checklist. § 17.10.040 · code text Upon confirmation by the building official of the application and supporting documentation being complete and meeting the requirement of the checklist, the building official shall administratively approve the application and issue all required permits or authorizations.
Solar height and setbacks	Panels may not be taller than the maximum legal building height. Applies: Required for a small home rooftop solar system to qualify for expedited permitting. § 17.04.020 · code text A solar panel or module array that does not exceed the maximum legal building height as defined by the City.
Solar permit process	Administrative, nondiscretionary review; the building permit is issued when the application meets the approved checklist and standard plan. Applies: Applies to complete small home rooftop solar applications. § 17.04.020 · code text The Building Division shall issue a building permit or other nondiscretionary permit [the same day for over-the-counter applications or within [one—three] business days for electronic applications] of receipt of a complete application and meets the requirements of the approved checklist and standard plan.
Review time	The permit is issued the same day. Applies: Applies to complete over-the-counter applications that meet the approved checklist and standard plan. § 17.04.020 · code text The Building Division shall issue a building permit or other nondiscretionary permit [the same day for over-the-counter applications or within [one—three] business days for electronic applications] of receipt of a complete application and meets the requirements of the approved checklist and standard plan. one—three business days Applies: electronic applications that are complete and meet the approved checklist and standard plan § 17.04.020 · code text The Building Division shall issue a building permit or other nondiscretionary permit [the same day for over-the-counter applications or within [one—three] business days for electronic applications] of receipt of a complete application and meets the requirements of the approved checklist and standard plan.

Swimming pools

San Marcos code What San Marcos's code adds
Pool barrier	No horizontal openings larger than 5 inches. Applies: Applies to swimming pool barriers. § 8.40.070 · code text Said barrier, wall, fence or structure shall be constructed or installed so as to prevent ladder-like access and shall have no horizontal openings greater than five inches. The barrier must prevent ladder-like climbing access. Applies: Applies to swimming pool barriers. § 8.40.070 · code text Said barrier, wall, fence or structure shall be constructed or installed so as to prevent ladder-like access and shall have no horizontal openings greater than five inches.
Barrier height	At least 5 feet tall, measured from the outside grade. Applies: Applies to pools on lots of 1 acre or less, and to hotel, apartment and public pools. § 8.40.070 · code text every swimming pool shall be enclosed by a natural barrier, retaining wall, fence or other structure having a minimum height of five feet measured from the exterior grade of said barrier, wall, fence or structure.
Gates	Gates must be self-closing and self-latching, with latches at least 4 feet 6 inches above the grade below. Applies: Applies to gates in the pool enclosure. Gates must stay securely closed and latched at all times. § 8.40.070 · code text All gates must be self-closing and self-latching, with latches placed at least four feet six inches above the grade immediately below the latch in order to be securely closed. All gates opening through such enclosure shall be kept securely closed and latched at all times.

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)

Who this affects

HomeownersContractorsDesigners

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).

How big can a shed or accessory building be in San Marcos?

Accessory structures are limited to 1 story and 15 feet, and may be no higher than the main home (city rule).

Can I run a business from my home in San Marcos?

A home business may use at most 200 square feet unless the Director approves more; only residents may work there.

Can I split my lot under SB 9 in San Marcos?

San Marcos's code: 2 parcels of about equal area; neither may be smaller than 40% of the original lot. (Applies to urban lot splits in a single-family residential zone.) (§ 19.44.050); Each new parcel must be at least 1,200 square feet. (§ 19.44.050).

Do I need a permit for solar panels or an EV charger in San Marcos?

San Marcos's code: Apply in person, by mail or online; the building official approves administratively and issues permits when the checklist is met. (Applies to complete applications with supporting documents that meet the checklist.) (§ 17.10.040); Panels may not be taller than the maximum legal building height. (Required for a small home rooftop solar system to qualify for expedited permitting.) (§ 17.04.020).

What are the pool fence and setback rules in San Marcos?

San Marcos's code: No horizontal openings larger than 5 inches. (Applies to swimming pool barriers.) (§ 8.40.070); The barrier must prevent ladder-like climbing access. (Applies to swimming pool barriers.) (§ 8.40.070).

General information, not legal advice.

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