Oregon Revised Statutes Mortgages and Liens § 87.030

(1) Every improvement except an improvement made by a person other than the landowner in drilling or boring for oil or gas, constructed upon lands with the knowledge of the owner shall be deemed constructed at the instance of the owner, and the interest owned shall be subject to any lien perfected pursuant to the provisions of ORS 87.001 to 87.060 and 87.075 to 87.093, unless the owner shall, within three days after the owner obtains knowledge of the construction, give notice that the owner will not be responsible for the same by posting a notice in writing to that effect in some conspicuous place upon the land or the improvement situated thereon.

(2) Subsection (1) of this section does not apply to a lien prohibited under ORS 87.037.