Can I build an accessory dwelling unit (ADU) in Casper?

Only on property zoned R-2 (One Unit Residential). Casper Municipal Code § 17.32.030(J) lists 'Accessory dwelling unit' as a conditional use in the R-2 district — it is not an allowed use in R-1, R-3, R-4, or R-5. A conditional use permit from the Planning and Zoning Commission is required, and either the principal home or the ADU must be owner-occupied. There is no separate ADU ordinance or dedicated permit fee; once the conditional use is approved, the ADU is built under the standard residential building permit process.

What are the ownership rules for an ADU in Casper?

Per the definition in Casper Municipal Code § 17.08.010, an accessory dwelling unit may not be subdivided or otherwise segregated in ownership from the principal dwelling unit, and either the principal dwelling or the ADU must be occupied by an owner of the property or an immediate family member of the owner.

Accessory Dwelling Unit (ADU) Permit in Casper, Wyoming

Verified

Casper Municipal Code Title 17 (Zoning) § 17.08.010 defines an 'accessory dwelling unit' as a habitable living unit added to, created within, or detached from a single-family dwelling that provides basic living, sleeping, eating, cooking, and sanitation facilities; either the principal or the accessory unit must be owner-occupied (or occupied by an immediate family member of the owner), and an ADU may not be subdivided or separated in ownership from the principal dwelling. Per § 17.32.030(J), an accessory dwelling unit is a CONDITIONAL USE in the R-2 (One Unit Residential) zoning district — it is not listed as permitted or conditional in R-1 (Residential Estate, § 17.28), R-3 (One to Four Unit Residential, § 17.36), R-4 (High Density Residential, § 17.40), or R-5 (Mixed Residential, § 17.44). There is no standalone ADU ordinance or ADU-specific permit fee; once the R-2 conditional use permit is approved by the Planning and Zoning Commission (procedure at § 17.12.240), the ADU is built under the standard residential building permit process (2024 IRC) and priced off the combined valuation-based fee schedule.

Verified 2026-07-01 · Source

$35Initial Building Permit Fee

When you need this permit

Property must be zoned R-2 (One Unit Residential) — Casper Municipal Code § 17.32.030(J) lists 'Accessory dwelling unit' as a conditional use in R-2 only; ADUs are not an allowed use in R-1, R-3, R-4, or R-5
A conditional use permit must be obtained from the Planning and Zoning Commission before applying for a building permit, per the conditional-use petition/hearing procedure in § 17.12.240 of Title 17
Per the ADU definition in § 17.08.010: either the principal dwelling unit or the ADU must be occupied by an owner of the property or an immediate family member of the owner
The ADU may not be subdivided or otherwise segregated in ownership from the principal dwelling unit (§ 17.08.010)
Once zoning/conditional-use approval is obtained, the ADU is built and permitted under the standard residential building permit process (2024 IRC), subject to R-2's general minimum standards in § 17.32.040 (lot area, lot width, setbacks)
Fee based on the value of construction per the combined valuation-based fee schedule (same schedule as new residential construction — no ADU-specific fee line exists)

Required documents

Req
Conditional Use Permit Application
Petition to the Planning and Zoning Commission for conditional-use approval of an ADU in an R-2 district, per Title 17 § 17.12.240
Req
Building Permit Application
Standard residential building permit application, submitted after conditional-use approval; ADUs follow the same submittal process as new residential construction
Req
Plot Plan
Site plan showing lot lines, existing structures, proposed ADU location, and parking
Req
Construction Drawings
Full plans for the ADU under the 2024 IRC

Fee schedule

Fee type	Amount	Notes
Initial Building Permit Fee	$35	City of Casper Permit Fee Schedule (eff. February 2, 2026)
Combined Building Permit Fee — valuation-based	Graduated table from $70 (valuation $1–$1,000) up to $841 (valuation $99,001–$100,000); over $100,000 = $806 + $5.60 per additional $1,000 or fraction thereof	City of Casper Permit Fee Schedule (eff. February 2, 2026); same fee structure as new residential construction — no ADU-specific fee line exists

Review timeline

~10–30 business days

Typical estimate — confirm current times with the Casper building department

Inspection process

1
Footer/Foundation
Before concrete pour
2
Framing
Structural framing and MEP rough-ins
3
Insulation
Proper R-values and placement
4
Final
All work complete, ready for occupancy

Tips

ADUs are a conditional use ONLY in the R-2 (One Unit Residential) zoning district per Casper Municipal Code § 17.32.030(J) — confirmed directly from the Title 17 zoning code text. Properties zoned R-1, R-3, R-4, or R-5 do not permit ADUs as either a permitted or conditional use.
Owner-occupancy is required: either the principal dwelling or the ADU itself must be occupied by the property owner or an immediate family member, per the ADU definition in § 17.08.010.
An ADU cannot be sold or subdivided separately from the principal dwelling — ownership must stay unified (§ 17.08.010).
Because ADU approval is a conditional use (not permitted-by-right) in R-2, expect a Planning and Zoning Commission hearing under the § 17.12.240 procedure before a building permit can be issued.
Because there is no dedicated ADU fee schedule, budget for the standard residential valuation-based building permit fee, not a flat ADU fee.
Confirm your parcel's zoning district with Planning/Zoning at (307) 235-8241 before designing — only R-2 parcels are eligible.

Frequently asked questions

Can I build an accessory dwelling unit (ADU) in Casper?: Only on property zoned R-2 (One Unit Residential). Casper Municipal Code § 17.32.030(J) lists 'Accessory dwelling unit' as a conditional use in the R-2 district — it is not an allowed use in R-1, R-3, R-4, or R-5. A conditional use permit from the Planning and Zoning Commission is required, and either the principal home or the ADU must be owner-occupied. There is no separate ADU ordinance or dedicated permit fee; once the conditional use is approved, the ADU is built under the standard residential building permit process.
What are the ownership rules for an ADU in Casper?: Per the definition in Casper Municipal Code § 17.08.010, an accessory dwelling unit may not be subdivided or otherwise segregated in ownership from the principal dwelling unit, and either the principal dwelling or the ADU must be occupied by an owner of the property or an immediate family member of the owner.

Sources & verification

Verified against official sources. Last reviewed 2026-07-01.

Fees, timelines, and adopted codes are researched from each jurisdiction's published records — see how we verify. Requirements change and vary by project, so always confirm the current details with the Casper building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.

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