ADU Design in New Castle, DE

ADU Design in Delaware: what governs your project

Delaware has no statewide ADU statute; ADU rules are set by counties and municipalities. Some jurisdictions, particularly in Sussex County, have established ADU provisions, while others handle them through conditional-use processes.

Energy code

Permitting is local, typically involving zoning compliance, setbacks, and building permits. Septic and well regulations matter in unsewered areas; fees and size limits vary by jurisdiction.

Permitting & plan check

Permitting in Delaware is handled at the county level — New Castle, Kent, and Sussex counties — plus incorporated cities such as Wilmington, Dover, and Newark. Larger or complex projects typically go through county land-use and site-plan review before building permits are issued.

Good to know

• Delaware has no state sales tax, which affects construction material and equipment procurement costs.
• Nearly the entire state lies within the Atlantic Coastal Plain physiographic province.
• The Interstate 95 corridor concentrates the state's heaviest commercial and industrial development.

Every discipline, one team