Retaining Walls: Brentwood vs Oakley
How do retaining walls rules compare between Brentwood, CA and Oakley, CA?
Brentwood and Oakley 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 →Oakley, CA
Contra Costa County
Retaining walls up to 3 feet (measured footing to top) are exempt from building permits in unincorporated Contra Costa County. Combined with a fence, the total height may not exceed 7 feet, and the wall portion may not exceed 3 feet.
View full Oakley rules →Key Facts Comparison
| Fact | Brentwood | Oakley |
|---|---|---|
| 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 | - |
| Grading trigger | >50 cu yd earthwork | - |
| Retaining wall exemption | - | Up to 3 feet |
| Combined fence + wall | - | 7 feet total, wall ≤ 3 ft |
| Code Section | - | Ord. Code 72-6.202 |
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.
Oakley FAQ
Can I stack a fence on top of a 3-foot retaining wall?
Yes, as long as the combined height of the wall and fence does not exceed 7 feet and the wall portion stays at or under 3 feet. This combined structure may be placed within required yard setbacks without planning approval.
When does a retaining wall need an engineered permit?
Whenever it exceeds 3 feet from footing to top, supports a surcharge (such as a driveway or sloped backfill steeper than 1:2), or impounds Class I, II, or III-a liquids.
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