Thornton, CO Swimming Pools & Spas: Pool Permits (2026)

Section 10-61(a) of the Thornton City Code makes a building permit mandatory before any person erects, constructs, or performs work regulated by the Building Code, and pool construction falls under that code through the city's adoption of the International Swimming Pool and Spa Code (ISPSC), 2024 edition, as the 'Swimming Pool and Spa Construction Code of the City' under Section 10-179. Section 10-180 locally amends the ISPSC's definitions, distinguishing a 'Residential Swimming Pool' (a pool accessory to a one- or two-family dwelling, available only to the household and its guests) from a 'Public Swimming Pool' operated for lodging uses such as hotels, apartments, or condominiums; the classification determines which construction and safety standards within the adopted code apply.

The building permit requirement for pools also surfaces in Chapter 22's grading rules: Section 22-114(2) exempts excavation for a swimming pool from the separate grading-permit requirement, but only when that excavation is 'authorized by a valid building permit,' meaning the pool's building permit must already be in place before digging starts. Building permits generally may be transferred to a new holder for a fee under Section 10-61(b) as long as the approved plans have not changed and the permit has not lapsed more than 180 days, and Section 10-61(c) makes clear that any work not specifically listed as exempt in the Building Code still needs a permit.