New Castle County

Home permits and project costs in Wilmington, DE

Wilmington sits in New Castle County, Delaware. Deep frost lines, snow load and a very old housing stock mean permits frequently touch structural, electrical and energy-code upgrades at once. Work outside city limits is permitted by the county building department rather than the city.

Model reviewed August 2026

Local cost index

+5%

vs national average

Permit fee index

-5%

vs national baseline

Population

71,106

Homeownership

Do you need a permit in Wilmington?

For most structural work, yes

Wilmington enforces local adoption of the irc by county and municipality through New Castle County. Roofing, electrical, plumbing, structural, pools and most exterior additions require a permit and inspection. Cosmetic work — paint, flooring, cabinet swaps — generally does not.

Project costs in Wilmington

National baselines adjusted by the local labor and materials index.

Project	Typical cost	Permit	Deep pages
Roof Replacement	$10,300 – $34,700	required	Cost·Permit
AC Replacement	$5,600 – $16,600	required	Cost·Permit
Fence Installation	$2,600 – $11,700	usually required	Cost·Permit
Water Heater Replacement	$1,300 – $5,800	required	Cost·Permit
Pool Installation	$40,900 – $123,700	required	Cost·Permit
Window Replacement	$8,100 – $36,600	required	Cost·Permit
Electrical Panel Replacement	$2,000 – $7,300	required	Cost·Permit
Generator Installation	$7,000 – $23,600	required	Cost·Permit
Solar Panel Installation	$16,000 – $51,200	required	Cost·Permit
Kitchen Remodel	$19,100 – $97,400	conditional	Cost·Permit
Bathroom Remodel	$9,500 – $44,500	conditional	Cost·Permit
Driveway Replacement	$4,500 – $20,300	usually required	Cost·Permit
Paver Patio & Walkway	$3,700 – $17,000	conditional	Cost·Permit
Deck Construction	$5,900 – $30,000	required	Cost·Permit
Shed Installation	$1,900 – $12,700	conditional	Cost·Permit
Whole-House Repipe	$4,800 – $17,200	required	Cost·Permit
EV Charger Installation	$900 – $4,500	required	Cost·Permit
Hurricane Shutter Installation	$3,500 – $19,500	required	Cost·Permit
Pool Enclosure / Screen Cage	$9,700 – $45,300	required	Cost·Permit
Septic System Replacement	$8,100 – $30,200	required	Cost·Permit
Impact Window Installation	$9,700 – $45,400	required	Cost·Permit
Exterior Door Replacement	$1,000 – $7,000	usually required	Cost·Permit
Garage Door Replacement	$1,500 – $8,100	required	Cost·Permit
Siding Installation	$8,600 – $40,800	usually required	Cost·Permit
Stucco Repair	$1,000 – $17,000	conditional	Cost·Permit
Soffit & Fascia Replacement	$1,900 – $11,800	conditional	Cost·Permit
Gutter Installation	$1,000 – $6,900	rarely required	Cost·Permit
Roof Repair	$400 – $5,200	conditional	Cost·Permit
Flat Roof Replacement	$6,500 – $30,300	required	Cost·Permit
Attic Insulation	$1,300 – $7,900	rarely required	Cost·Permit
Ductwork Replacement	$2,700 – $12,800	required	Cost·Permit
Mini Split Installation	$2,600 – $13,400	required	Cost·Permit
Flooring Installation	$2,600 – $21,100	rarely required	Cost·Permit
Tile Installation	$1,900 – $16,900	rarely required	Cost·Permit
Interior Painting	$1,600 – $10,100	rarely required	Cost·Permit
Exterior Painting	$3,000 – $15,900	rarely required	Cost·Permit
Drywall Repair	$400 – $4,800	rarely required	Cost·Permit
Kitchen Cabinet Refacing	$4,800 – $21,200	rarely required	Cost·Permit
Countertop Replacement	$2,300 – $12,600	rarely required	Cost·Permit
Tub to Shower Conversion	$3,700 – $17,100	usually required	Cost·Permit
Sod Installation	$900 – $7,400	rarely required	Cost·Permit
Irrigation System Installation	$2,300 – $10,600	conditional	Cost·Permit
Tree Removal	$500 – $5,900	conditional	Cost·Permit
Outdoor Kitchen	$6,400 – $48,100	usually required	Cost·Permit
Seawall Repair	$8,700 – $102,800	required	Cost·Permit
Dock Construction	$9,700 – $92,000	required	Cost·Permit
Well Installation	$5,900 – $26,900	required	Cost·Permit
Mold Remediation	$1,600 – $16,000	conditional	Cost·Permit
Water Softener Installation	$1,300 – $6,900	usually required	Cost·Permit
Home Addition	$48,600 – $302,700	required	Cost·Permit
Heat Pump Replacement	$6,900 – $23,500	required	Cost·Permit
Furnace Replacement	$3,400 – $12,300	required	Cost·Permit
Foundation Repair	$3,000 – $34,100	usually required	Cost·Permit
Basement Waterproofing	$3,200 – $19,100	conditional	Cost·Permit
Drain Field Replacement	$6,400 – $26,800	required	Cost·Permit
Toilet Installation	$300 – $1,200	rarely required	Cost·Permit
Hot Tub Installation	$5,900 – $23,500	usually required	Cost·Permit

Wilmington permitting basics

Jurisdiction	Wilmington, New Castle County
Building department	Confirm with the city or county
Permit portal	No verified online portal on file
Owner-builder permits	Owner-builder permits generally allowed
Contractor verification	Verify any license with Delaware Division of Small Business before signing

Sources

Sources & verification

Delaware Division of Small Business

Model vintage August 2026. The links above are the issuing agencies' own pages — we publish them so you can confirm the current rule yourself, not as evidence that each fact on this page was re-checked with them today. Cost figures are modeled estimates based on national baselines adjusted for local labor and material pricing, not quotes. Permit rules change; confirm with the building department before starting work.