Retaining Walls: Altadena vs Santa Monica
How do retaining walls rules compare between Altadena, CA and Santa Monica, CA?
Altadena and Santa Monica have similar restriction levels.
Altadena, CA
Los Angeles County
Retaining walls in unincorporated LA County under 4 ft from footing to top are exempt from building permits unless supporting a surcharge. Walls in required yards cannot exceed 6 ft. In coastal areas, retaining walls must be terraced and landscaped with native species before the rainy season (Oct 15-Apr 15).
View full Altadena rules →Santa Monica, CA
Los Angeles County
Retaining walls in Santa Monica over 4 ft in Seismic Design Category D, E, or F cannot be constructed of wood. Fence height on top of retaining walls is measured from lowest grade within 3-ft radius. Engineering required for significant walls.
View full Santa Monica rules →Key Facts Comparison
| Fact | Altadena | Santa Monica |
|---|---|---|
| Permit Exempt | Under 4 ft height | - |
| Yard Maximum | 6 ft in required setbacks | - |
| Coastal | Must terrace and landscape | - |
| Engineering | Soils report for taller walls | Required for significant walls |
| Wood Prohibited | - | SDC D/E/F over 4 ft |
| Height Measurement | - | From lowest grade within 3 ft |
| Seismic | - | AWPA U1 treatment required |
Highlighted rows indicate differences between cities.
Altadena FAQ
Do I need a permit for a retaining wall in LA County?
Only if the wall exceeds 4 feet from footing to top. Walls over 4 feet need a building permit and engineered plans from a licensed engineer. Contact Building & Safety at (626) 458-3171.
Can I build multiple short walls instead of one tall one?
Tiered walls with less than the height of the lower wall between them are measured as a single wall for permit purposes. This prevents circumventing the 4-foot permit threshold.
What if my retaining wall is failing?
A failing retaining wall is a safety hazard. Contact Building & Safety at (626) 458-3171 immediately. You may need emergency repairs and a geotechnical evaluation. You are liable for damage to adjacent properties.
Santa Monica FAQ
Do I need a permit for a retaining wall?
In Santa Monica, walls over 4 feet typically require a building permit and engineered plans. Shorter walls may be exempt.
How close to the property line can I build a retaining wall?
Setback requirements vary. Check Santa Monica zoning code for specific distances from property lines.
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