Longmont, CO Building Setbacks & Zoning: Setback Rules (2026)

Setbacks are measured under Section 15.03.080.C.1 as the distance between the nearest property line and the closest projection of a building or structure, taken at right angles to that line; unless a feature is exempted, the setback must stay unobstructed from the ground to the sky. Rear setbacks from a non-dedicated alley are measured instead from the fence line, or from the closest edge of the travel lane if there is no fence.

The residential table sets the R-RU district at a 20-foot front yard, 10-foot side yard, 20-foot rear yard, and 6 feet where the rear abuts an alley. R-MH manufactured-home parks get a 10-foot front yard, 5-foot side yard, 15-foot rear yard, and a 20-foot setback along any perimeter facing a public right-of-way. Building height in these districts runs 35 feet in R-RU, R-SF and R-MN and 55 feet in R-MF, subject to the residential compatibility standards in Section 15.05.200.D, while R-MH is capped at 20 feet for dwellings and 35 feet for other structures.

Section 15.03.080.C.4 lets an applicant in a residential district use a contextual setback instead of the table figure: the mean average of existing front setbacks on the same and facing block face, available only where more than half the lots on that block face are already built with dwellings, with vacant lots counted at the district's minimum. Section 15.03.080.C.10 and Table 15.03.080(1) list specific encroachments: eaves and cornices up to 2 feet, uncovered decks under 24 inches high, front porches up to 8 feet if they stay 5 feet off the line, ground-mounted mechanical equipment up to 5 feet, and storage sheds under 120 square feet at least 3 feet from the line. No structure may encroach into an easement, and lots adding at least 12 percent affordable housing qualify for a 20 percent reduction in minimum lot area and width under Section 15.03.080.B.1.b.

Corner and other multiple-frontage lots must meet the front setback requirement on every street-facing side under Section 15.03.080.C.6. Swimming pools, hot tubs, and spas may encroach into a required side or rear yard if they meet building code requirements and are designed to accommodate lot drainage; window wells may project up to 3 feet into a setback; and uncovered slabs, patios, sidewalks, and driveways may sit within 3 feet of the property line, or right on the line for a shared driveway. Every building must also comply with the oil and gas facility setbacks in Section 15.05.090, and cluster lot subdivisions in the R-RU and N-AG districts can reduce these setbacks further under Section 15.07.040.