Building Addition Permit

Required for any construction that expands the footprint or volume of an existing residential or commercial building in Wisconsin. Additions must comply with the UDC for residential structures or SPS 361–366 for commercial buildings, including setback requirements, structural tie-ins, and energy code compliance for the new section.

Verified 2026-02-01
Typical Fee Range
$300–$3,500
flat
Typical Timeline
2–5 weeks for plan review
From application to approval
Inspection Required
Yes
One or more inspections required
Jurisdiction Level
Municipal
Issuing authority level

When Is a Building Addition Permit Required?

  • Room additions that expand the building footprint
  • Second-story additions to existing structures
  • Bump-out additions (kitchen, bedroom, bathroom)
  • Sunroom or four-season room additions with HVAC

When Is a Building Addition Permit NOT Required?

  • Interior remodeling within existing walls
  • Screened porches without HVAC or insulation in some municipalities

Related Permits You May Also Need

Residential Building Permit
Required for new single-family homes, duplexes, and multi-family dwellings in Wisconsin. The state enforces the Uniform Dwelling Code (UDC) statewide through DSPS, but municipalities issue permits and conduct inspections locally. Plans must comply with SPS 320–325 for structural, energy, and safety requirements.
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Electrical Permit
Required for all electrical installations, alterations, and repairs in Wisconsin. The state adopts the National Electrical Code (NEC) with Wisconsin-specific amendments under SPS 316. All electrical work on residential dwellings must be performed by a licensed master or journeyman electrician, or by a homeowner on their own single-family residence.
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Plumbing Permit
Required for all plumbing installations, alterations, and repairs in Wisconsin. The state's plumbing code (SPS 381–387) is among the most detailed in the nation. All plumbing work must be performed by a Wisconsin licensed master or journeyman plumber, with very limited homeowner exemptions.
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HVAC/Mechanical Permit
Required for installing, replacing, or significantly modifying heating, ventilation, and air conditioning systems in Wisconsin. Covers furnaces, boilers, air conditioners, heat pumps, ductwork, and ventilation systems. Residential HVAC falls under the UDC; commercial systems under SPS 363–364. Wisconsin requires HVAC credentials through DSPS for most installations.
→

Required Licenses

The following professional licenses may be required to obtain or work under this permit type in Wisconsin.

Building Addition Permit Fees by Municipality

Fee and processing time data for building addition permit permits across Wisconsin municipalities. Click any jurisdiction for complete details including application links and requirements.

JurisdictionFeeProcessing TimeStatus
City of Milwaukee$100 + $8 per $1,000 valuation3-5 weeksCurrent
City of Madison$85 + $9 per $1,000 valuation2-4 weeksCurrent
City of Green Bay$75 + $7 per $1,000 valuation2-3 weeksCurrent
City of Kenosha$80 + $7.50 per $1,000 valuation2-3 weeksCurrent
City of Racine$70 + $6.50 per $1,000 valuation2-3 weeksCurrent
City of Appleton$70 + $6 per $1,000 valuation1-3 weeksCurrent
City of Waukesha$90 + $8 per $1,000 valuation2-3 weeksCurrent
City of Oshkosh$65 + $5.50 per $1,000 valuation1-3 weeksCurrent
City of Eau Claire$60 + $5 per $1,000 valuation1-3 weeksCurrent
City of Janesville$55 + $5 per $1,000 valuation1-2 weeksCurrent

Data note: Fees are sourced from official municipal fee schedules and verified periodically. Actual fees may vary based on project valuation and scope. Click any jurisdiction for the most current data and direct application links.

Frequently Asked Questions — Building Addition Permit

Do I need a permit for a home addition in Wisconsin?

Yes. Any construction that expands the footprint, height, or volume of your home requires a building permit in Wisconsin. The municipality will review plans for structural integrity, setback compliance, and UDC conformance before issuing the permit.

How much does a building addition permit cost in Wisconsin?

Addition permits in Wisconsin typically cost $300 to $3,500, calculated based on the estimated construction value of the new space. Most municipalities use a per-$1,000-of-value formula similar to new construction permits.

Does a home addition need to meet current building codes in Wisconsin?

Yes. The new addition must comply with the current version of Wisconsin's Uniform Dwelling Code, even if the existing home was built under older standards. The existing structure generally does not need to be brought up to current code unless the addition creates a safety concern.

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