You can face fines of $350 per day if you build the wrong fence without approval in unincorporated San Mateo County. So before I plan a fence, I first check who controls the property, then I look at height, material, location, Coastal Zone status, and whether the fence sits on a retaining wall.
Here’s the short version:
- Jurisdiction comes first. Unincorporated county parcels follow county rules. City parcels follow city rules.
- A building permit is usually needed for:
- fences over 6 feet
- masonry or concrete fences at any height
- fences on top of a retaining wall
- Many wood and chain-link fences that meet zoning rules may not need a building permit.
- Zoning rules still apply even when no building permit is needed.
- Front-yard and street-facing corner fences in unincorporated areas are often capped at 4 feet.
- Rear and interior side-yard fences are often capped at 6 feet.
- Corner lots can face tighter sight-distance rules within 50 feet of intersecting streets.
- Coastal Zone parcels may need a Coastal Development Permit and do not use the standard fence height exception path.
- A Fence Height Exception may allow up to 2 extra feet outside the Coastal Zone, but it can cost about $2,600 and take 2 to 4 months.
- I also need to check property lines, grade, HOA rules, right-of-way issues, and neighbor notice before building.
If I had to sum it up in one line: a fence that seems simple can still trigger county, city, coastal, public works, or planning review based on where and how it’s built. That’s what this guide helps sort out.
When a Fence Permit Is Required
In San Mateo County, a fence permit usually comes down to height, material, and where the fence sits. Another big factor: whether the fence is placed on top of a retaining wall.
Height, material, and retaining wall conditions that require a permit
A building permit is required for:
- Any masonry or concrete fence, no matter the height
- Any fence over 6 feet tall
- Any fence built on top of a retaining wall
County rules are pretty direct here. Fences above retaining walls need a building permit, while wooden or cyclone fences that meet zoning rules do not.
If your project also needs zoning approval, that step has to happen first. A common example is a Fence Height Exception. That approval can allow up to 2 extra feet beyond the standard height limit, costs about $2,600, and usually takes 2 to 4 months to process.
Even if your fence doesn't trigger the retaining-wall rule, its location can still change what review is needed.
Permit scenarios by location: front yard, backyard, corner lot, and street side yard
These limits apply in unincorporated San Mateo County. Incorporated cities may use different rules.
In most cases, front yards and the street-facing side of a corner lot are limited to 4 feet. Rear yards and interior side yards are usually limited to 6 feet.
| Fence Location | Standard Height Limit |
|---|---|
| Front yard | 4 feet |
| Street-facing side of a corner lot | 4 feet |
| Rear yard | 6 feet |
| Interior side yard | 6 feet |
| On a retaining wall | Varies |
| Masonry or concrete | Any height |
Any fence above 6 feet needs a building permit, even if you also get a Fence Height Exception.
Corner lots add another layer. Within 50 feet of intersecting street lines, fences, walls, and hedges are limited to 4 feet to protect sight distance. If you want to go taller in that area, the County may ask for a sight-distance study prepared by a licensed civil engineer.
Permits for commercial, multi-family, coastal, and security fence projects
Rules get tighter when the project isn't a basic single-family residential fence. Commercial, multi-family, coastal, and security fence projects often go through extra review before a building permit is issued.
In Design Review (DR) districts, planning approval must come first. Some projects may also be reviewed by:
- Fire
- Public Works
- Civil/Drainage
- Geotechnical staff
If the fence is in the public right-of-way, you'll also need a separate encroachment permit from Public Works.
Properties in the Coastal Zone have their own track. Fence work there requires a Coastal Development Permit or an exemption, and those properties are not eligible for a standard Fence Height Exception.
When a project hits more than one review trigger, the approval path usually starts with zoning review, then moves to the building permit, followed by any special permit such as a coastal or encroachment permit.
When a Permit May Not Be Required
Some fence projects can skip a building permit. But that does not mean you can build whatever you want. Zoning rules still set the limits.
Residential fence projects that often skip a building permit
County rule: Wood and cyclone fences that meet zoning rules usually do not need a building permit. In many cases, a backyard wood or chain-link fence that is 6 feet or less does not need one either.
There’s one catch: replacement fences still have to follow today’s zoning rules. So if the old fence didn’t comply, the new one may need an exception.
No building permit still means zoning rules apply
This is where people get tripped up. A fence may be exempt from a building permit and still break the rules if it crosses a property line or ignores setback rules.
Height limits, setbacks, and corner-lot sight distance rules apply to every fence, permit or not. In unincorporated San Mateo County, the first 20 feet of a side lot line behind the front yard and the first 10 feet on the street side of a corner lot are limited to 4 feet. If you add lattice on top, that lattice counts toward the total fence height.
A fence can look fine from the yard and still sit in the wrong place. Do not use an existing fence to confirm setbacks. Fences often do not match the actual property line.
A boundary survey from a licensed surveyor is recommended before construction. And if your property is inside an incorporated city, check the local code first, because city rules may differ from unincorporated county standards.
Next, review height, setback, and neighbor-notice rules before you build.
Height Limits, Setbacks, Property Lines, and Other Rules That Affect Approval
Front-yard, side-yard, rear-yard, and corner-lot fence limits
Fence height is measured from the lowest adjacent natural grade. That sounds simple, but it trips people up all the time. On a sloped lot, a fence that looks fine from one side can still be over the limit because the county measures from the lower natural ground next to it.
That’s why fence projects often get flagged in review. The issue usually isn’t the base height rule by itself. It’s how that rule changes based on grade, fence location, and lot shape.
Corner lots get tighter limits, especially where a fence faces a street. On a corner lot, fences can’t be taller than 4 feet on any street-facing side. And within 50 feet of intersecting street lines, that same 4-foot cap applies to protect sight distance. If a fence goes over that limit in a corner location, the county may ask for a sight-distance study from a civil engineer.
There’s another spot people miss: the first 20 feet of an interior side yard behind the front yard. In that area, the fence is also capped at 4 feet. After those 20 feet, the limit can move to 6 feet. This is one of the most common reasons a plan that looks fine on paper gets pushed back.
| Fence Location | Standard Height Limit | Key Note |
|---|---|---|
| Interior Side Yard (first 20 feet from front yard) | 4 feet | Transitions to 6-foot limit beyond 20 feet |
| Street-Facing Side (corner lot) | 4 feet | Applies to any side facing a street |
| Corner Lot (within 50 feet of intersection) | 4 feet | Sight-distance safety rule |
Outside the Coastal Zone, a Fence Height Exception can allow up to 2 extra feet.
Shared boundary fences, neighbor notice, and California Civil Code 841
Under California Civil Code 841, adjoining property owners share equal responsibility for fences on a shared boundary. In plain English, that usually means the cost, upkeep, and choices tied to that fence are a joint matter by default.
If you’re building on or near a shared boundary line, give your neighbor notice before work starts.
One more thing: an existing fence does not prove where the property line is. Plenty of old fences sit a little off. Before building, use a licensed surveyor to confirm the line.
HOAs, lot conditions, and local exceptions
HOAs may comment during permit review. So even if the county is the main approval body, an HOA can still affect the process.
Lot conditions matter too. If the slope is over 10%, the plot plan must include contour lines so the county can check fence height from natural grade.
If the project needs both a Fence Height Exception and a building permit, get the planning permit first.
Once those height, setback, and property-line rules are sorted out, the next step is pulling together the documents and approvals the county will want.
How to Plan the Permit Process and Avoid Delays
Documents, site details, and agency checks to prepare first
Start by confirming where the parcel sits before you file anything. You need to know whether it’s in unincorporated San Mateo County, an incorporated city, or the Coastal Zone. You should also check coastal status and parcel conditions in the County Planning GIS tool.
After that, pull together the main documents. In most cases, you’ll need a site plan that shows property lines, setbacks, and the exact fence location. If the fence will be taller than 6 feet, you’ll also need elevation drawings that show the height, material, and design.
Some sites need extra prep. If the parcel has expansive soils or liquefaction risk, you may need a soils report when footing depth goes beyond 18 inches. That report can add about $800 to $2,500 to pre-permit costs.
Before any digging starts, call 811 through USA North to have underground gas and electric lines located. With your site plan in hand, it also makes sense to confirm utility lines and check any HOA rules before filing.
Project type matters too. Standard residential jobs usually move through fewer reviews. Commercial and more complex projects often go through full plan check and may be sent to Fire and Public Works, along with extra permits such as encroachment, grading, or Coastal Development permits. If the project needs both planning and building permits, get planning approval first.
How A-1 Fence Company can help with permit-sensitive projects
A-1 Fence Company works with residential and commercial clients across the San Francisco Bay Area on permit-sensitive projects. That can make a big difference early on, especially when material choice and fence placement affect whether a permit is needed. Some heights and materials can trigger added review, and those details are easier to deal with before installation than after.
Working with an installer who knows those permit triggers from the start can help cut down on corrections, rework, and filing slowdowns.
FAQs
How do I know if my property is in unincorporated San Mateo County or a city?
Check whether your address falls under a city or town government. The Development Review Center handles permits for unincorporated San Mateo County. If your property is inside an incorporated city or town, you’ll need to contact that local government instead.
Not sure where your address belongs? Reach out to the San Mateo County Planning and Building Department for help.
Does replacing an old fence still require approval under current rules?
It comes down to the fence type, height, and where the fence sits.
In unincorporated San Mateo County, wooden or cyclone fences that are 6 feet or shorter usually don’t need a building permit if they follow local zoning rules. Once a fence goes over 6 feet, or if it’s a masonry fence, or the work is in a public right-of-way, you’ll need approval.
In the City of San Mateo, the permit cutoff is 7 feet. If you’re doing a full fence replacement, the new fence has to follow the current rules for height and location.
What permits might I need if my fence is in the Coastal Zone or right-of-way?
If your fence project is in the Coastal Zone, you'll often need planning review first. That can include a Coastal Development Permit before you apply for a building permit.
If the fence extends into the public right-of-way, you also need an encroachment permit from San Mateo County Public Works. And if a right-of-way fence is taller than 4 feet, it needs a separate Fence Height Exception. One catch: that exception is not available for parcels in the Coastal Zone.