Retaining Walls: Brentwood vs Walnut Creek
How do retaining walls rules compare between Brentwood, CA and Walnut Creek, CA?
Brentwood and Walnut Creek have similar restriction levels.
Brentwood, CA
Contra Costa County
Retaining walls in Brentwood up to 4 feet in height measured from the bottom of the footing to the top of the wall generally do not require a building permit if they do not support a surcharge (driveway, slope, or structure). Walls over 4 feet or supporting a surcharge require a building permit with engineered drawings.
View full Brentwood rules →Walnut Creek, CA
Contra Costa County
Retaining walls up to four feet tall measured from the bottom of the footing to the top of the wall generally do not require a permit in Walnut Creek, while walls over four feet or supporting surcharge loads require a building permit with engineered design.
View full Walnut Creek rules →Key Facts Comparison
| Fact | Brentwood | Walnut Creek |
|---|---|---|
| No-permit threshold | Up to 4 ft, no surcharge | - |
| Permit required | >4 ft or any surcharge | - |
| Engineering | Licensed CA engineer stamp | - |
| Drainage | Required behind wall | Must not runoff to neighbor |
| Grading trigger | >50 cu yd earthwork | - |
| Permit-exempt max | - | 4 feet (no surcharge) |
| Permit trigger | - | Over 4 ft or any surcharge |
| Engineer stamp | - | Required for permitted walls |
| Fence on top | - | Measured from high-side grade |
Highlighted rows indicate differences between cities.
Brentwood FAQ
Do I need a permit for a 3-foot garden wall?
Not if it's a freestanding decorative wall under 4 feet with no soil or slope pressing against it. If it retains any slope or drive, even a 2-foot wall may require a permit and engineering.
Can I build a retaining wall on the property line?
Generally yes, subject to setbacks and the Good Neighbor Fence Act for any boundary fence on top. Walls supporting a neighbor's soil or structure require a written agreement or easement, and the neighbor must be notified.
Walnut Creek FAQ
Do I need a permit for a 3-foot retaining wall?
Generally no, provided it does not support any surcharge load such as a driveway, structure, or stored materials above the retained earth. If there is a surcharge, a permit is required regardless of height.
Can I put a 6-foot fence on top of a retaining wall?
The combined structure is measured from the finished grade on the high side of the wall for fence-height purposes. A 6-foot fence on top of a retaining wall will exceed the standard 6-foot fence limit when viewed from the low side and will likely require a variance or building permit.
Compare other topics
See how Brentwood and Walnut Creek compare on other ordinance categories.
Want to add a third city?
Use our full comparison tool to compare up to three cities.
Open Comparison Tool