Bolthole Index

Washington County, Wisconsin

Zoning, building permits and septic rules in the Town of Trenton, Wisconsin

The Town of Trenton in Washington County, Wisconsin has its own zoning code1 and requires a building permit from the Town Building Inspector before most new building work begins2. Septic permits come from Washington County, not the town3. Where the Wallace Lake Sanitary District sewer reaches, private septic systems are prohibited after the hookup notice4. We could not confirm the town's rules for RVs or tiny homes5.

At a glance

Building permit
Required from the Town Building Inspector for new buildings and covered alterations2
Zoning
The town has its own zoning code, adopted by the Town Board1
Septic
Washington County Sanitary Permit; county inspectors check the installation36
Sewer
Connection required within 90 days of notice from the Wallace Lake Sanitary District where its sewer reaches7
Driveway
Driveway/culvert permit from the Town Building Inspector8
Minimum home size
One-story houses: 1,300 sq ft with a full basement, 1,600 sq ft without9
Manufactured homes
Count as single-family dwellings in the cited residential districts; mobile homes excluded10
RV and tiny home living
Not confirmed; ask the Town Administrator5

Who to call

Building permits

Town of Trenton Building Inspector

Town building permits, driveway/culvert permits and inspections inside the Town of Trenton

(262) 675-0909

building@townoftrenton.wi.gov

1071 Highway 33 E, West Bend, WI 53095

Zoning

Town of Trenton Administrator & Zoning

Town zoning questions, zoning action, conditional use and variance applications

(262) 290-0154

townadmin@townoftrenton.wi.gov

1071 Highway 33 E, West Bend, WI 53095

Septic permits

Washington County Natural Resources Department — Land Resources

County sanitary (septic) permits, erosion-control and stormwater applications

(262) 335-4445

landres@washcowisco.gov

333 E. Washington Street, Suite 2300 P.O. Box 2003 West Bend, WI 53095-2003

Online permits →

Roads & driveways

Washington County Highway Department

Access permits for driveways and culverts on County Trunk Highways

Contact details are copied from each office’s official page and were checked against it on October 15, 2026.

Off-grid gear

Going off-grid in Town of Trenton means bringing your own water and power. The kit we’d start with:

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Does the Town of Trenton, Wisconsin have zoning, and what does it mean for lot size and setbacks?

Yes. The Town of Trenton adopted its own zoning code and divides the town into zoning districts111. Washington County does not administer general zoning, so the town code, not the county, decides what you can build on a Trenton parcel12.

Dimensional rules depend on the district. In the R-3 Rural Residential District, lots need at least three acres and 300 feet of width13, and buildings may not exceed 35 feet in height14. Manufactured homes count as single-family dwellings in the cited residential districts, but mobile homes are excluded, and district lot, size and setback rules still apply10.

The Town Building Code also sets a minimum size for one-story houses: 1,300 square feet of heated living area with a full basement, or 1,600 square feet without one9. Ask the Town Administrator which district your parcel is in before you buy5.

Do you need a building permit in the Town of Trenton, and who issues it?

Yes. The Town of Trenton Building Inspector issues building permits, and the town code requires one before any new building or structure is erected, enlarged, altered, moved or demolished2. Minor repairs valued under $250 may proceed without a permit if they do not change occupancy, exterior appearance, structural strength, fire protection, exits, light or ventilation2.

The town adopts Wisconsin's Uniform Dwelling Code for one- and two-family homes15. Applications go on a form from the Building Inspector, and one- and two-family homes in residentially zoned districts are excepted from site-plan approval16. The Building Inspector must inspect within two business days after you call, at stages that include footings, framing, insulation and completion17. A certificate of occupancy follows when the work conforms18.

A homeowner who lives in a single-family home may do their own electrical work with an electrical permit, except on subpanels, generators and wiring for hot tubs, spas or pools19. Applications and plans can be emailed to the town's permit address20.

How do septic permits work in the Town of Trenton?

Washington County, not the town, handles septic permits for every address in the Town of Trenton. Installing or repairing a septic system requires a Washington County Sanitary Permit3, and a county Land Use Inspector checks the installation through a series of inspections6. A Master Plumber or Master Plumber-Restricted Sewer must obtain the permit and do the work, and the application needs a site plan, site evaluation and system design3. Certain systems also need state approval before the county permit6.

Sewer changes the answer. Where a Wallace Lake Sanitary District sewer main runs next to a parcel with a habitable building, the owner must connect within 90 days of written notice7. In the district's serviced area, septic tanks and private sewage systems are prohibited 90 days after the hookup notice; outside that area, county septic permitting applies4. Across Washington County, about 15% of soils rate as not limited for a conventional drain field on USDA's strict scale, so expect a site evaluation and possibly an engineered system21. Call the county Land Resources office22.

Can you live in an RV or tiny home on your land in the Town of Trenton?

We could not confirm the Town of Trenton's rules for living in an RV, camping on private land, or occupying a tiny home. The town code chapters we reviewed did not state an explicit rule, so do not assume either answer. Ask the Town Administrator before you buy or park anything5.

One county rule is clear for mapped floodplain land under Washington County's floodplain ordinance: a tiny home used as a principal dwelling is prohibited in the Floodway District23. In the Floodfringe District, it is allowed only if the standards of the county's floodfringe section are met, including elevating a new residence on fill24. Check the floodplain map for your parcel with the county before you commit.

A manufactured home installed as a single-family dwelling is a different case: the town code treats it as a single-family dwelling in the cited districts10.

Building a home in the Town of Trenton: the steps, in order

  1. Confirm the parcel's zoning district with the Town Administrator, and check lot area, width and minimum house size for that district513.
  2. Ask Washington County Land Resources about a sanitary permit, or the Wallace Lake Sanitary District about sewer223.
  3. For work outside an existing footprint, the town's Building Inspector page points to a Washington County permit sign-off and the county's online portal20.
  4. Apply for the building permit with the Town Building Inspector; new homes need plans220.
  5. Get a driveway/culvert permit from the Building Inspector before installing a driveway8.
  6. Call for inspections at each stage; the inspector has two business days to respond17.
  7. Receive the certificate of occupancy when the work passes18.

What stays with Washington County, and what to check before you buy in Trenton

Beyond septic, several rules come from the county or state, not the town. Washington County's shoreland, wetland and floodplain ordinance covers land within 300 feet of a river or navigable stream, within 1,000 feet of a lake or pond, and mapped floodplain and wetlands25. County approval applies to subdivisions of five or more parcels of 1.5 acres or less within five years, and the township must also approve26.

A driveway onto a County Trunk Highway needs a county access permit27; the town's culvert permit covers driveways entering town roads8. Residential driveway openings must be at least 10 feet at the lot line and no more than 25 feet at the roadway8.

For land outside the town, see the Washington County page. Washington County's effective property tax rate is about 1.2%28, and the nearest city of 100,000 or more is about 25 miles from the county center29.

Watch-outs

  • Three Wisconsin towns are named Trenton; the Town of Trenton's building page says to submit permit applications only to the Washington County town and not to the Dodge or Pierce County towns of the same name20.
  • We could not confirm the town's rules for RV living, temporary camping, tiny homes or short-term rentals; ask the Town Administrator before relying on any of them5.
  • A parcel in the Wallace Lake Sanitary District's serviced area may be required to connect to sewer instead of installing septic7.
  • A county shoreland or floodplain permit can apply on top of the town building permit near water25.

Sources

  1. Town of Trenton, WI Code of Ordinances (Town of Trenton), quoted and re-checked
  2. Chapter 174: Building Construction (Town of Trenton), quoted and re-checked
  3. Septic Systems/POWTS - Washington County, WI (Town of Trenton), quoted and re-checked
  4. Chapter 325: Sewers (Town of Trenton), quoted and re-checked
  5. Town of Trenton Administrator & Zoning (townoftrenton.wi.gov)
  6. Septic Systems/POWTS - Washington County, WI (Town of Trenton), quoted and re-checked
  7. Chapter 325: Sewers (Town of Trenton), quoted and re-checked
  8. Chapter 174: Building Construction (Town of Trenton), quoted and re-checked
  9. Chapter 174: Building Construction (Town of Trenton), quoted and re-checked
  10. Article III: Zoning Districts (Town of Trenton), quoted and re-checked
  11. Article III: Zoning Districts (Town of Trenton), quoted and re-checked
  12. County Land Information Plan 2024, quoted and re-checked
  13. Article III: Zoning Districts (Town of Trenton), quoted and re-checked
  14. Article III: Zoning Districts (Town of Trenton), quoted and re-checked
  15. Chapter 174: Building Construction (Town of Trenton), quoted and re-checked
  16. Chapter 174: Building Construction (Town of Trenton), quoted and re-checked
  17. Chapter 174: Building Construction (Town of Trenton), quoted and re-checked
  18. Chapter 174: Building Construction (Town of Trenton), quoted and re-checked
  19. Chapter 174: Building Construction (Town of Trenton), quoted and re-checked
  20. Town of Trenton Building Inspector (townoftrenton.wi.gov)
  21. Share of soils USDA rates "not limited" for a conventional septic drain field (SSURGO). A strict rating: the median county is about 6% and a tenth of counties are 0%, so a low figure means most lots need a site evaluation or an engineered system, not that septic is impossible. Cite it only with that caveat: Bolthole Index county data
  22. Washington County Natural Resources Department — Land Resources (permitapp.washcowisco.gov)
  23. Article IV: Floodplain Zoning - Washington County, WI, quoted and re-checked
  24. Article IV: Floodplain Zoning - Washington County, WI, quoted and re-checked
  25. washcowisco.gov, quoted and re-checked
  26. Land Division, quoted and re-checked
  27. Permits, quoted and re-checked
  28. Effective property tax rate: Bolthole Index county data
  29. Straight-line distance from the county center to the nearest city of 100,000+ people: Bolthole Index county data

Written October 15, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.

Answers from the rulebook for Town of Trenton

Town of Trenton’s own rules

  • Building permitRequired

    New buildings, structures, and covered alterations, moves, demolitions, uses, and street-opening utility work inside Trenton town.

    • A permit must be obtained from the Building Inspector before the covered work begins.
    • Minor repairs valued at less than $250 may be authorized without a permit if they do not change occupancy area, exterior appearance, structural strength, fire protection, exits, light, or ventilation.
    “No building of any kind shall be moved within or into the Town and no new building or structure, or any part thereof, shall hereafter be erected, or ground broken for the same, or enlarged, altered, moved, demolished, razed or used within the Town, or utility services installed or utility services repaired or replaced which involve the opening of the street, except as herein provided, until a permit therefor shall first have been obtained by the owner, or his/her authorized agent, from the Building Inspector.”
  • Owner-builder exemptionConditional

    A homeowner performing electrical work on an owner-occupied single-family dwelling inside Trenton town.

    • The homeowner may not perform the listed work on electrical service subpanels, generators, or wiring to hot tubs, spas, or swimming pools.
    • An electrical permit is required.
    • The work must be inspected and approved as for a licensed electrician.
    • The homeowner may be required to provide drawings or plans.
    “A homeowner himself or herself may do electrical work on a single-family dwelling, if he or she owns and occupies it as his or her permanent residence, excluding duplex or multifamily residences, except that he/she may not repair or replace the electrical service subpanels in any building to such dwelling or generators or install electrical wiring to hot tubs, spas or swimming pools.”
  • Building code adoptedAdopted

    Building construction inside Trenton town, including one- and two-family dwellings and commercial buildings.

    • The Town adopts Wisconsin Uniform Dwelling Code provisions and Wisconsin commercial, plumbing, and electrical codes by reference.
    “The Administrative Code provisions describing and defining regulations with respect to one- and two-family dwellings in Chs. Comm 20 through 25 are hereby adopted and by reference made a part of this chapter as if fully set forth herein.”
  • InspectionsRequired

    Permitted building work inside Trenton town.

    • The builder must notify the Building Inspector when ready.
    • Inspections occur at footings/foundation, framing and rough systems, insulation, completion, utility-meter installation, and as otherwise required.
    • The Building Inspector must inspect within two business days after notification.
    “The builder shall notify the Building Inspector when ready for inspections, and the Building Inspector shall inspect within two business days after notification all buildings at the following states of construction:”
  • Certificate of occupancyRequired

    Buildings receiving the Town's required building inspections inside Trenton town.

    • The certificate is issued if the Building Inspector finds the work conforms to the chapter.
    • The certificate contains the inspection date and result.
    “If he/she finds that the work conforms to the provisions of this chapter, he/she shall issue a certification of occupancy which shall contain the date and the result of such inspection, a duplicate of which shall be filed in the office of the Building Inspector.”
  • Local zoningPresent

    Zoning inside the Town of Trenton.

    • The zoning code was adopted by the Town Board on 11-7-1989; amendments are noted in the code.
    “For the purpose of this Zoning Code, the Town of Trenton is hereby divided into the following districts:”
  • Zoning districtsPublished

    Zoning districts inside Trenton town.

    • The code lists EA, AT, AE, A-1, R-1 through R-8, B-1, B-2, M-1, I-1, I-2, P-1, CES-5, CES-10, PDO, and C-1 districts.
    • District boundaries follow the Town zoning map unless otherwise noted.
    “For the purpose of this Zoning Code, the Town of Trenton is hereby divided into the following districts:”
  • Minimum dwelling sizeSpecified

    One-story single-family residential houses in Trenton town under the Town building code.

    • With a full basement, at least 1,300 square feet of heated living area is required.
    • Without a full basement, at least 1,600 square feet is required.

    heated living area: >= 1300 square feet (one-story house with full basement) · heated living area: >= 1600 square feet (one-story house without full basement)

    “Each one-story single-family residential house shall contain at least 1,300 square feet of heated living area if said house has a full basement. If said house does not have a full basement, it shall have at least 1,600 square feet of heated living area.”
  • Minimum lot sizeSpecified

    Lots in the R-3 Rural Residential District.

    • Lots must be at least three acres and at least 300 feet wide.

    minimum lot area: >= 3 acres · minimum lot width: >= 300 feet

    “Lot area and width. Lots shall have a minimum area of three acres and shall be not less than 300 feet in width.”
  • Building heightSpecified

    Buildings in the R-3 Rural Residential District.

    • The cited maximum applies to buildings or parts of buildings.

    maximum building height: <= 35 feet

    “No building or parts of a building shall exceed 35 feet in height.”
  • Manufactured homesLimited

    Manufactured homes used as single-family dwellings inside Trenton town zoning districts.

    • The code states manufactured homes are included in the single-family-dwelling definition, while mobile homes are excluded in the cited residential districts.
    • District-specific zoning, attached-garage, septic/sewer, lot, size, and setback requirements still apply.
    “Single-family dwellings with an attached garage, excluding all mobile homes; for purposes of this chapter, manufactured homes are included in the definition of "single-family dwelling."”
  • Who permits septicCounty

    Private on-site wastewater systems inside Trenton town; Washington County is the permit and inspection authority.

    • Certain POWTS require state approval before the County sanitary permit.
    • The County Land Use Inspector inspects compliance with state codes.
    “A Washington County Land Use Inspector will ensure that the POWTS is installed in compliance with state codes through a series of inspections.”
  • Septic permitRequired

    Installation or repair of septic systems inside Trenton town.

    • The owner must obtain a Washington County Sanitary Permit.
    • A Master Plumber or Master Plumber-Restricted Sewer is responsible for obtaining the permit and installation or repair.
    • The application requires an application, site plan, site evaluation, and system design.
    • Certain POWTS require state approval before the County permit.
    “Activities relating to the installation or repair of septic systems requires the owner of the property to obtain a Washington County Sanitary Permit.”
  • Septic inspectionRequired

    Installation of POWTS inside Trenton town.

    • Washington County conducts a series of inspections for compliance with state codes.
    “A Washington County Land Use Inspector will ensure that the POWTS is installed in compliance with state codes through a series of inspections.”
  • Off-grid sanitationLimited

    Private sewage disposal inside the Wallace Lake Sanitary District-serviced area in Trenton town.

    • Septic tanks and other private sewage disposal systems are prohibited after sewer completion and written hookup notice.
    • Outside that serviced area, Washington County POWTS permitting applies.
    “From and after 90 days after completion of construction of the sanitary sewer system and notice in writing to hook up per § 325-8, the use of septic tanks or any private sewage disposal system within the area of the Wallace Lake Sanitary District serviced by the sewerage system shall be prohibited.”
  • Mandatory utility hookupSewer (with conditions)

    Parcels inside Trenton town adjacent to a Wallace Lake Sanitary District sewer main or in a block through which the sewer system is extended.

    • Connection is required within 90 days after written notice from the Wallace Lake Sanitary District.
    • The District may make the connection and bill the owner if the owner fails to connect.
    • Within the serviced area, septic tanks and private sewage systems are prohibited 90 days after sewer completion and written hookup notice.

    connection deadline: 90 days after written notice

    “The owner of each parcel of land adjacent to a sewer main on which there exists a building usable for human habitation or in a block through which such system is extended shall connect to such system within 90 days of notice in writing from the Wallace Lake Sanitary District.”
  • Driveway accessRequired

    Driveways entering public rights-of-way inside Trenton town.

    • A culvert is required for a driveway in the public right-of-way, including agricultural field-access and residential or commercial driveways.
    • A driveway/culvert permit must be obtained from the Building Inspector before installation.
    • Residential openings must be at least 10 feet at the lot line and no more than 25 feet at the roadway.

    culvert minimum diameter: >= 15 inches (unless sized otherwise by Building Inspector) · culvert minimum length: >= 24 feet (unless sized otherwise by Building Inspector) · residential opening at lot line: >= 10 feet · residential opening at roadway: <= 25 feet

    “Before installing a driveway/culvert, a permit must first be obtained from the Building Inspector.”
  • Permit processPublished (with conditions)

    Town building-permit applications inside Trenton town.

    • Applications are written on a Building Inspector form and state owner, land, legal description, designer, intended use, and other required information.
    • Certain construction requires site-plan approval; one- and two-family residences in residentially zoned districts are excepted.
    • The Town Board authorizes or refuses permits within 30 days after receiving a referred application.

    Town Board action period: <= 30 days (after receipt of application)

    “Application for a building permit shall be made in writing upon a form furnished by the Building Inspector or his/her designee and shall state the name and address of the owner of the land and also the owner of the building, if different, the legal description of the land upon which the building is to be located, the name and address of the designer, the use to which said building is to be put and such other information as the Building Inspector may require.”

Still unanswered

We looked and could not find an official answer yet. Silence is not permission; ask Town of Trenton or Washington County directly.

  • Lot coverage — Lot coverage inside Trenton town.
  • Living in an RV — RV occupancy on private land inside Trenton town.
  • Camping on your land — Temporary camping inside Trenton town.
  • Tiny homes — Tiny-home occupancy inside Trenton town.
  • Agricultural exemption — Agricultural building or land-use exemptions inside Trenton town.
1 more unanswered
  • Short-term rentals

Each answer was extracted from an official source and independently re-checked against that source by a second reviewer. That is an evidence check, not legal advice. Rules change; confirm with the authority before you buy or build.

Unanswered questions are usually a sign that Town of Trenton publishes no rule on the point, not that none exists. Washington County’s page lists the county offices to call.

← All of Washington County: county rules, score and offices