Standards for Installing Mailboxes on County Roads

Roadside mailboxes need to be strong to stand up to the elements, convenient for the mail carrier to reach inside and installed to ensure safety for passersby.

Please follow the guidelines below to make sure your mailbox meets these requirements.

Safety comes first

This policy allows for mailboxes and paper delivery boxes within the Clackamas County right-of-way. The specifications described in this publication are designed to help everyone provide a safe transportation system for travelers.

Clackamas County requires that mailboxes and newspaper delivery boxes located within the right-of-way be constructed and installed in a manner that does not substantially interfere with either:


Mailbox diagram


A mailbox installation that does not conform to the provisions of this policy will be considered a safety hazard. Any violation could result in action by County Code Enforcement and potential fines.

Mailbox location


Mailboxes are typically installed with the bottom of the mailbox located 41 to 45 inches above the roadway surface. Refer to your local post office regulations for specific mailbox height requirements.

Number of mailboxes on one post:

No more than two mailboxes may be mounted on one support post, unless the support structure and mailbox arrangement meet the American Association of State Highway and Transportation Officials (AASHTO) standards.

Eliminating fixed objects on roadside:

Clackamas County standards ensure that the roadside remains free of fixed objects that can be dangerous to travelers, and prohibits planting or constructing an object along a road that will visually obstruct the view necessary for safe operation of motor vehicles on the road.

  • In general, non-breakaway objects should be located 7 - 15 feet from the edge of the travel lane, depending on the type of road.
  • If possible, a mailbox should be located so that a vehicle stopped at it is clear of the adjacent travel lane. (Exceptions may be made for very low-volume, low-speed, local roads.)
  • Careful consideration should be given to determining the location of the mailbox to ensure that vehicles exiting driveways have unobstructed views of vehicles traveling on the roadway.

Mailbox diagram

Support system

The mailbox support system should be anchored no more than 24 inches into the ground, as shown above.

Urban areas

  • Mailboxes that are located in urban areas should be installed in such a way so the front of the mailbox is set back from the face of the curb by 6 to 12 inches.
  • If the sidewalk is next to the curb and the mailbox obstructs the required width of the sidewalk, provisions should be made to widen the sidewalk around the mailbox so the sidewalk's unobstructed width requirement is met.
  • Placing mailboxes of any type along high-speed, high volume roads should be avoided if other practical locations are available.

Approved mailbox installations

A typical mailbox installation should consist of a light, sheet-metal box mounted on one of the breakaway support systems shown below, anchored no more than 24 inches into the ground.

Prohibited mailbox installations

Mailboxes supported by structures such as non-breakaway masonry columns, railroad rails and ties, tractor wheels, plow blades and concrete barrels -- including those shown below -- may not be installed along County roads.

For more information

More information about mailbox installation standards is available in Section 7.03.090 of the County's Road Use Ordinance and Section 245 of Clackamas County Roadway Standards.

Questions or comments?

Contact us at or 503-742-4691.