Clackamas County, OR Accessory Structures: ADU Impact Fees (2026)
Key Facts
- ADU TSDC classification
- ITE code 220, Apartment rate
- When charge is due
- At development/building permit issuance
- Statutory authority
- ORS 223.297 to 223.314
- Guest homes
- Exempt; ADUs with own kitchen are not
- Appeal fee
- $1,110 deposit plus actual costs
- Installment option fee
- $528 application fee
Summary
Accessory dwelling units in unincorporated Clackamas County are not exempt from the county's Transportation System Development Charge. Under County Code Section 11.03.020(A), a ZDO-839-compliant ADU is billed at the Institute of Transportation Engineers "220 - Apartment" rate, due before a development or building permit is issued.
ACCESSORY DWELLING UNIT means a unit complying with Clackamas County ZDO 839. Accessory Dwelling Units will be charged the adopted rate for the Institute of Transportation Engineers (ITE) classification of "220 - Apartment."
B. AFFILIATE is any entity that directly controls, is controlled by or under common control with the applicant. As used herein, the term "control" or "controlled by" means the power to direct the management of such entity through voting rights, ownership or contractual obligations.
C. ARTERIAL means that term as defined and used in Chapter 5 - Transportation System Plan of the County Comprehensive Plan.
D. AVERAGE WEEKDAY TRIPS means the average 24-hour total of all vehicle trips counted to and from a study site from Monday through Friday. Average Weekday Trips are calculated by using the Institute of Transportation Engineers (ITE) Manual or as otherwise provided by this Chapter.
E. ASSIGNMENT refers to the transfer of a credit voucher or portion of a credit voucher that is transferred to another party.
F. BOARD means the Board of County Commissioners of Clackamas County, Oregon.
G. BUILDING OFFICIAL means that person, or their designee, certified by the State and designated as such to administer the State Building Codes for the County.
Full Breakdown
Clackamas County imposes a Transportation System Development Charge (TSDC) on new development under Chapter 11.03, using authority granted by ORS 223.297 through 223.314 to fund transportation capacity for growth. Section 11.03.020(A) defines an Accessory Dwelling Unit for TSDC purposes as "a unit complying with Clackamas County ZDO 839," and specifies that "Accessory Dwelling Units will be charged the adopted rate for the Institute of Transportation Engineers (ITE) classification of '220 - Apartment.'" The charge is calculated from the Rate Schedule the Board adopts by resolution under Section 11.03.010(E) and is adjusted every fiscal year for construction-cost inflation under Section 11.03.030(J), using the Engineering News Record Northwest Construction Cost Index.
Per Section 11.03.040(A), the TSDC is "due and payable at the time of issuance of the Development Permit," and the permit cannot issue until it is paid except where a credit-voucher delay applies. Not every accessory unit pays: Section 11.03.030(C)(1) exempts "Guest Homes" that share a kitchen and laundry with the primary dwelling because they are not separately habitable, but an ADU with its own kitchen and laundry does not qualify for that exemption and is charged the full Apartment-classification rate. A property owner who disputes the fee calculation can appeal under Section 11.03.080(B) by filing a written request and paying the appeal fee, currently $1,110 deposit plus actual costs per the county's adopted fee schedule (Code Section 11.03.080.B), within 14 days of the Department's decision.
Violations & Fines
A Development or Building Permit for an ADU will not be issued until the TSDC is paid in full, per Section 11.03.040(A); the only exceptions are the installment-payment option under Section 11.03.040(D) (a $528 application fee under Section 11.03.040.D.1) or an approved credit-voucher delay. Disputing the fee requires filing a written appeal with the Hearings Officer and paying the $1,110-deposit-plus-actual-costs appeal fee under Section 11.03.080(B) within 14 days of the Department's decision or payment, whichever comes first.
Frequently Asked Questions
Are ADUs exempt from Clackamas County's transportation development charge?
How much is the ADU transportation fee in Clackamas County?
When do I have to pay the ADU TSDC?
Can I appeal my ADU's transportation fee calculation?
Sources & Official References
Other rules in Clackamas County
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