Tippecanoe County, IN Accessory Structures: ADU Rules (2026)

Section 4-12 of the Unified Zoning Ordinance is the county's whole framework for accessory dwelling units, and it only reaches unincorporated Tippecanoe County's rural zones, never the incorporated cities or towns on the joint zoning map. To add an ADU by right through new construction or an addition, § 4-12(b) requires the existing lot and its single-family home to already meet the zone's lot width, lot area, lot coverage and vegetative-cover ratios without ever having needed a variance; a lot that only qualifies because of a granted variance can still add an internal ADU by right under § 4-12(c), and a noncomplying lot can convert an existing accessory structure to a detached ADU, but only by variance.

Only one ADU is allowed per lot under § 4-12(d), and if the principal home is on sewer and public water, the ADU has to share those same laterals; septic and well properties go through Health Department review instead. Size is capped at 50% of the principal dwelling's ground-floor area, or up to 400 square feet if that 50% figure comes in under 400, and a detached ADU, including one carved out of a larger accessory building like a pole barn, cannot exceed 1,200 square feet under § 4-12(e).

Occupancy is limited to one family beyond whoever lives in the principal dwelling, per § 4-12(f), and § 4-12(g) requires the property owner to actually live on site, in either unit, as their primary residence. Detached units need a 6-foot separation from the principal dwelling and must meet the zone's accessory-building setbacks under § 4-12(i). Before the county issues the permit, § 4-12(m) requires a recorded deed restriction keeping the principal dwelling and ADU in common ownership and the lot owner-occupied.