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Unincorporated King County
TDRs may be used in certain areas of unincorporated King County. Unincorporated King County includes parcels regulated by King County zoning which are those not located within an incorporated city.
Basic criteria for receiving sites are outlined below. The TDR Code has the detailed criteria for receiving sites.
Areas qualified to receive TDRs include:
- Unincorporated King County urban areas zoned R-4 through R-48, NB, CB, RB, or O. In zones R-4 through R-48 there may be opportunities for low-cost TDRs to apply to development projects with certain affordability provisions as described in 21A.37.130.
- Rural areas zoned RA-2.5 if TDRs originate in a Rural Forest Focus Area and all of the following conditions are also met:
- The site is served by a domestic Group A public water service;
- The site is within ¼ mile of an existing predominant pattern of lot sizes smaller than 5 acres;
- The project will not adversely impact regionally or locally significant resource or environmentally sensitive areas; and
- The project will not require public services and facilities to be extended in order to create or encourage a new pattern of smaller lots.
The following areas cannot receive TDRs under any circumstances:
- Properties on Vashon or Maury Islands,
- Properties within the Rural Forest Focus Area, or
- Properties within the outer boundaries of the Noise Remedy Area identified by Sea-Tac International Airport.
Allowed increases in density using TDRs
|
Zone |
Description |
Base Density (du/ac)* |
Maximum Density (du/ac) |
|
RA-2.5 |
Rural Area |
0.2 |
0.4** |
|
R-4 |
Residential |
4 |
6 |
|
R-6 |
Residential |
6 |
9 |
|
R-8 |
Residential |
8 |
12 |
|
R-12 |
Residential |
12 |
18 |
|
R-18 |
Residential |
18 |
27 |
|
R-24 |
Residential |
24 |
36 |
|
R-48 |
Residential |
48 |
72 |
|
NB |
Neighborhood Business |
8 |
12 |
|
CB |
Community Business |
18 |
24 |
|
RB |
Regional Business |
36 |
48 |
|
O |
Office |
36 |
48 |
|
* du/ac = dwelling units per acre (see density) |
Using development rights on a receiving site
TDRs may be used in several ways at qualified receiving sites:
- To increase density (typically 50%) above what is allowed by the base zoning.
- To increase Floor Area Ratios (typically 50%) above what is allowed by base zoning.
When you apply to King County for a residential building permit or apply to subdivide land, you will need to supply proof that you own the development rights. Proof of ownership consists of a TDR certificate, or a TDR letter of intent in your name, or a signed and notarized option to purchase development rights from someone who owns a certificate or a letter of intent. Proof of ownership is sufficient to start the King County review process on your development application. (See additional information about permits from King County Permits).
Before receiving a building permit or final plat or short plat recording, you will need to deliver to King County a TDR certificate in your name for the number of transferrable development rights you wish to apply at the site.
Following permit issuance, you will need a TDR extinguishment document that shows the TDRs have been used and cannot be used again on another project.
For TDR transactions within unincorporated King County, each Rural TDR allows two additional units in urban receiving areas; each Urban TDR allows one additional unit.
To learn more:
- Buying and Selling TDRs in King County
- King County TDR Exchange
- TDRs currently for sale in the TDR Exchange