Retaining Walls: Boulder vs Longmont
How do retaining walls rules compare between Boulder, CO and Longmont, CO?
Boulder and Longmont have similar restriction levels.
Boulder, CO
Boulder County
Boulder requires permits for retaining walls above a certain height, typically 4 feet. Engineering review may be required for taller walls.
View full Boulder rules →Longmont, CO
Boulder County
Longmont does not publish a stand-alone retaining-wall guide; walls are regulated under the adopted 2021 International Building Code (IBC) and 2021 International Residential Code (IRC), enforced by Building Services. Under IRC R404.4 and IBC standards, a permit is generally required when a retaining wall exceeds 4 feet measured from the bottom of the footing to the top of the wall, or when the wall supports a surcharge (slope, driveway, structure).
View full Longmont rules →Key Facts Comparison
| Fact | Boulder | Longmont |
|---|---|---|
| Permit Free | Up to 4 feet typically | - |
| Engineering | Required over 4 feet | - |
| Setbacks | Apply near property lines | - |
| Drainage | Must be addressed | - |
| Adopted Code | - | 2021 IBC and 2021 IRC (effective Jan. 1, 2022) |
| Permit Threshold | - | Greater than 4 ft (footing to top), per IRC R404.4 |
| Surcharge Walls | - | Permit required at any height if surcharge or structural load |
| Sight Triangle Limit | - | 36 in solid / 42 in if 50% open (LMC 15.05.100) |
| Engineering Required | - | Walls greater than 4 ft or surcharge walls need stamped design |
| Next Code Cycle | - | 2024 I-Codes effective July 1, 2026 |
Highlighted rows indicate differences between cities.
Boulder FAQ
Do I need a permit for a retaining wall?
In Boulder, 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 Boulder zoning code for specific distances from property lines.
Longmont FAQ
Do I need a permit for a retaining wall in Longmont?
Under the city's adopted 2021 IRC (Section R404.4), a permit is required for any retaining wall exceeding 4 feet measured from the bottom of the footing to the top of the wall, or for any wall that supports a surcharge such as a slope, driveway, or structure.
Does a short garden wall need a permit?
Generally no - a landscape or garden wall under 4 feet that retains only soil and carries no surcharge does not require a building permit. It must still comply with LMC 15.05.100 sight-triangle rules and may not block drainage or easements.
Which building code does Longmont follow for retaining walls?
The 2021 International Building Code and 2021 International Residential Code, adopted effective January 1, 2022. The city plans to adopt the 2024 I-Codes on July 1, 2026.
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