Boulder County, CO Fence Regulations: Retaining Walls (2026)
Key Facts
- Permit threshold
- Over 48 inches (4 feet)
- Measured
- Footing bottom to wall top
- Design standard
- International Building Code
- Counted as fence?
- No, walls are separate
- Surcharge walls
- Permit even if under 4 feet
Summary
In unincorporated Boulder County a retaining wall over 48 inches (4 feet), measured from bottom of footing to top, requires a building permit. Retaining walls are not counted as fences and must meet International Building Code structural design standards.
The term fence does not include retaining walls. Also, fences built around a developed use... must meet other zoning, land use, and Building Code standards. Retaining walls and masonry fences must meet the structural design standards of the International Building Code.
Full Breakdown
Boulder County distinguishes retaining walls from fences: 'The term fence does not include retaining walls.' Per the county's building permit guidance, retaining walls over 48 inches (4 feet) in height require a building permit; shorter walls are generally exempt unless they support a surcharge (an added load such as a slope, driveway, or structure above) or impound Class I, II, or IIIA liquids. Retaining walls and masonry fences must meet the structural design standards of the International Building Code. Because Boulder County is mountainous, engineered wall designs are common. These standards apply to the unincorporated county; municipalities set their own thresholds.
Violations & Fines
Building a retaining wall over 4 feet without a permit is a code violation; the county may require a stamped engineered design, permit, inspection, or removal of noncompliant walls.
Frequently Asked Questions
When does a retaining wall need a permit?
Is a retaining wall the same as a fence?
Sources & Official References
Other rules in Boulder County
Compare Boulder County to another location·View the Colorado fence regulations overview
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