Ascension Parish, LA Accessory Structures: ADU Impact Fees (2026)

Ascension Parish charges a transportation impact fee on new development under Chapter 19, Article III, assessed at 95 percent of the base fee schedule east of the Mississippi River and 35 percent west of the river, collected when a building permit or certificate of occupancy is applied for. Code § 19-50(b)(2) carves out a specific exemption for homeowners adding a secondary family residence: an addition, remodeling, or other improvement to an existing home is exempt from the fee so long as it does not add dwelling units or floor area, or adds no more than 1,000 square feet built for a secondary family residence occupied by a family member as defined in section 19-48 and expressly including a father-in-law or mother-in-law.

Section 19-48 defines a secondary family residence as housing for immediate family members, children, grandchildren, parents, or grandparents of the property owner, capped at whatever density the land use district allows, with conservation districts limited to secondary single-family residences. To claim the exemption, an owner submits an application to the transportation impact fee administrator (§ 19-50(b)(6)) with a site survey showing the existing structure and proposed improvement, plus documentation confirming no additional dwelling units are created, the use has not changed, and no additional vehicle trips result.

Any claim must be filed no later than the date of the building permit application, or, if no permit is required, no later than when the addition opens for use. The parish council cannot waive or negotiate impact fees outside this exemption list under § 19-50(e).