Sussex County, DE Accessory Structures: ADU Rules (2026)

Sussex County Code § 115-20A(15) treats an accessory dwelling unit as an administratively approved use in the AR-1 and AR-2 Agricultural Residential Districts, the zoning that covers most of unincorporated Sussex County outside the beach towns. The applicant pays a fee set by County Council rather than a fixed dollar figure printed in the code, and must submit a survey signed and sealed by a Delaware-licensed surveyor to the Director showing where the ADU will sit and the floor area of both the ADU and the primary dwelling.

Two size caps apply together: the ADU cannot exceed 1,000 square feet, and it cannot exceed 50% of the floor area of the single-family home already on the lot, whichever is smaller. At least one dedicated parking space must be set aside for the unit, and it cannot encroach into any required yard setback. On a lot smaller than three acres, a detached ADU must sit behind the main dwelling. The county will not approve an ADU on a lot under 10,000 square feet at all.

Because approval runs through the Director rather than the Board of Adjustment, there is no public hearing built into the ordinance text itself; the process is administrative. A related special use exception at § 115-23C(5) lets the Board of Adjustment consider ADUs that do not meet the § 115-20A(15)(c), (d) and (e) dimensional limits, giving an appeal-like path for units that exceed the size, setback or lot-size rules.