City Hall, 100 N. Jefferson Street, Room 608, Green Bay, WI 54301
Phone: (920) 448-3300 (8 AM–4 PM)
Website: greenbaywi.gov/permits →
Green Bay room addition permit rules — the basics
Room additions in Green Bay require building and trade permits at City Hall, 100 N. Jefferson Street, Room 608. Phone: (920) 448-3300. Long project permit application required. Wisconsin SPS codes + Green Bay local ordinances govern. Wisconsin DSPS Dwelling Contractor Certification AND Qualifier Certification required. Call 811 before foundation excavation.
Green Bay's frost depth of 48–60 inches is the dominant foundation design requirement. All addition footings must extend below the frost line. This is deep enough to justify full basement construction as an economically efficient option — once footings reach 4–5 feet, extending to 7–8 feet for a full basement adds minimal excavation cost while providing highly functional space. Green Bay homeowners adding room additions frequently add basement space simultaneously.
Wisconsin SPS Energy Conservation (Chapter SPS 363) for Climate Zone 6 imposes significant energy requirements on new conditioned space: attic insulation R-49 minimum, wall insulation R-20 or R-13+5 continuous, foundation wall insulation R-10 to R-15, window U-factor 0.32 maximum. These are substantially more demanding than Climate Zone 3A requirements in Texas or Allen. Energy documentation is required with the permit application.
Wisconsin SPS does not require seismic engineering for Green Bay additions — Wisconsin is in a low seismic zone. Wisconsin SPS structural provisions and snow load requirements govern addition framing and connection design.
| Variable | How it affects your Green Bay addition permit |
|---|---|
| 48–60 inch frost depth | The deepest in this guide. All footings must reach below frost line. Economical to add full basement at this excavation depth. Call 811 before excavation. |
| Climate Zone 6 energy code | Attic R-49 min, walls R-20 or R-13+5, foundation R-10–15, windows U-0.32 max. Very demanding energy requirements. Energy documentation required with permit application. |
| Basement option: economically logical | At 48–60 inch excavation depth, adding a full basement is economically efficient. Green Bay additions frequently include basement expansion. |
| Wisconsin SPS snow load provisions | Northeast Wisconsin ~45 inches annual snowfall: addition framing and roof must meet Wisconsin SPS snow load requirements for Green Bay area. |
| Wisconsin DSPS Dwelling Contractor Certification | Both certifications required. Owner-occupants of primary single-family residence may do own work with permit. |
What room additions cost in Green Bay
Bedroom addition (no basement, 300–400 sq ft): $58,000–$95,000. With basement: $65,000–$115,000. Combined permit fees: contact (920) 448-3300 for current schedule.
Common questions about Green Bay WI room addition permits
How do I apply for a room addition permit in Green Bay?
Long project permit application submitted in-person at City Hall, 100 N. Jefferson Street, Room 608. Phone: (920) 448-3300. Wisconsin DSPS Dwelling Contractor Certification required. Call 811 before foundation excavation.
How deep do addition footings need to be in Green Bay?
Green Bay's frost depth is approximately 48–60 inches — the deepest in this guide. All addition footings must extend to this depth. At this excavation depth, adding a full basement is often economically logical since the marginal cost of extending from 4–5 feet to 7–8 feet is relatively small compared to the usable space gained.
What energy code governs Green Bay room additions?
Wisconsin SPS Chapter 363 for Climate Zone 6: attic insulation R-49 minimum, wall insulation R-20 or R-13+5 continuous, foundation wall insulation R-10 to R-15, windows U-factor 0.32 maximum. These are far more demanding than Climate Zone 3A (Texas/Allen) or Climate Zone 4A (Topeka). Energy documentation is required with the permit application.
Does Green Bay require seismic engineering for additions?
No. Wisconsin is in a low seismic zone. Wisconsin SPS codes do not require seismic engineering for residential additions in Green Bay. Wisconsin SPS structural provisions and snow load requirements govern addition framing.
Can I add a basement when building a room addition in Green Bay?
Yes. Given Green Bay's 48–60 inch frost depth requires deep excavation anyway, many Green Bay homeowners add basement space simultaneously with a room addition. Discuss the option with your Wisconsin DSPS-certified Dwelling Contractor to evaluate the incremental cost and benefit for your specific project.
Wisconsin Public Service (WPS) — Green Bay's dual-utility provider
Unlike most cities in this guide where electricity and natural gas are provided by separate companies, Green Bay is served by Wisconsin Public Service (WPS) for both electricity and natural gas. WPS, a subsidiary of WEC Energy Group headquartered in Green Bay, serves approximately 474,000 electric customers and 350,000 natural gas customers in northeast and central Wisconsin. The single-utility structure means Green Bay homeowners coordinate with one company for all energy service changes: panel upgrades, gas line modifications, meter disconnects, and solar interconnection all route through WPS.
WPS customer service: 800-450-7260. Electric emergency: 800-450-7240. Gas emergency: 800-450-7280. For construction-related service changes (meter disconnects for panel upgrades, gas meter changes for gas line work), coordinate with WPS alongside the City of Green Bay Building Inspection Division permit at (920) 448-3300. WPS offers net metering for solar installations; verify current net metering terms at wisconsinpublicservice.com before finalizing solar system design. WPS customers may also be eligible for Wisconsin Focus on Energy rebates for energy efficiency and renewable energy improvements.
Wisconsin SPS codes — how Green Bay building codes differ from most states
Wisconsin uses the Safety and Professional Services (SPS) code system — the Wisconsin Department of Safety and Professional Services's own regulatory code framework — rather than the International Code Council (ICC) codes used by most other states. The Wisconsin Uniform Dwelling Code (UDC, encompassing SPS 320–325 for residential construction), Wisconsin Commercial Building Code (SPS 361–366), and Wisconsin Plumbing Code (SPS 382–387) are Wisconsin's own code structure with Wisconsin-specific provisions.
For homeowners and contractors, the practical implication is that Wisconsin-specific code requirements apply rather than the 2018 IRC or 2021 IRC that governs most other states in this guide. Wisconsin's energy code (SPS 363) reflects Climate Zone 6 requirements that are substantially more demanding than zones applicable to Texas, Oklahoma, or Florida. Wisconsin's contractor certification requirements (Dwelling Contractor Certification + Qualifier Certification through DSPS) are Wisconsin-specific and separate from any national contractor certification. Green Bay Building Inspection Division enforces Wisconsin SPS codes alongside local Green Bay municipal ordinances. Contact (920) 448-3300 for current code requirements applicable to your specific project.
City of Green Bay Building Inspection Division. Wisconsin DSPS certification required. Contact (920) 448-3300 for current permit fee schedule. Not engineering advice.