The minimum front setback shall be 20 feet. Except that the minimum setbacks from Logan Road need not exceed the average setback of buildings on all lots within 100 feet of the lot on the same side of the street which the proposed building is to be located and that abut Logan Road. The applicant shall retain the services of an Oregon-licensed land surveyor to prepare and submit a survey, at the applicant's sole cost and expense, when averaging is proposed to be used to determine the setback. The 20-foot front setback shall not apply to elevated decks that extend from the dwelling wall into the front setback; provided, that the lowest point of the elevated deck structure is a minimum of seven feet above grade and a minimum 15-foot setback is maintained. Permitted encroaching decks may be either cantilevered or supported by posts and beams if the posts and beams meet all building and fire code requirements, and the posts and beams are not within the minimum 15-foot setback.