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HomeMy WebLinkAboutEngineer ReportKURTZ & ASSOCIATES, INC. 5012 County Road 154 Glenwood Springs, CO 81601 STRUCTURAL CONSULTANTS Phone (970) 945 6305 MEMORANDUM To : Garfield County Building & Planning Department April 13 , 2015 Re : Structural Inspection: Auxiliary Dwelling Unit (ADU) Addition 341 Homestead Drive, Garfield County, CO. The purpose of this site inspection was to establish the code compliance and structural integrity of the noted ADU . The ADU is a recent addition to an existing Agricultural Storage building . I understand that the agricultural building was constructed approximately nine (9) years ago, and that the ADU addition was constructed in the fall of 2014 . The ADU encloses what was a carport as part of the original construction . In addition to the site inspection, I also reviewed construction documents which had been prepared by the contractor. The documents depict the ADU and the original agricultural building . As constructed, the building, including the ADU addition, is a single story structure. The building measures, in plan , approximately 40' -0" north-to-south by 54' -0" east-to-west. A 12'-0" (east-to-west) by 40 '-0" addition was added to the west side of the original building to accommodate the intended ADU . A center ridge line runs north- to-south and the roof pitch each side of the ridge is 4 / 12. At this time the structure is complete, and is a weather tight structure . Interior finishes have not been installed in the section designated as the ADU . The building site elevation is approximately 7200 feet above sea level. Based upon the elevation, the design snow load for the roof= 50 PSF . The building is a wood framed structure . The building and the ADU addition can be described as a post and beam structure with pole building details for the foundation . It is better described as a post and frame building: Four (4) lines of 6 x 6 pressure treated timber posts are constructed at 1 O' -0" on center. The post lines extend east-to-west so that there is a line of posts at the north and south exterior walls, and there are three (3) interior post lines. The 54'-0" east-to-west length of the building consists of center 30 '-0" bay which is framed with site built roof trusses. The east and west wings each measure 12 '-0" east-to-west by 40'-0". At the post lines (at I0 '-0" on center) wood sawn 2 x 12 beams span 12'-0" from post-to-post. At the north and south exterior walls the beams are single 2 x 12 's. At the interior post and beam lines the beams are spaced, double 2 x 12's. The 2 x 12 beams are bolted to the top of the posts . As noted, the foundation is a pole building type foundation in that the construction documents detail the posts embedded (2) 4, -0" into the earth in a 12" diameter hole and encased in concrete. The embedded post base in combination with the bolted roof beam to post detail creates significant frame action. The resultant structure is laterally rigid and redundant. Double 2 x 6 purlins spaced at 24" on center span 10, -O" between the 2 x 12 beams . All of the roof framing is structurally adequate to safely resist a design snow load of 50 PSF . The construction documents detail a well reinforced concrete slab-on-grade for the agricultural building and the ADU addition. The documents detail a 4" thick concrete slab with 1/2" diameter (No . 4's) rebar spaced at 24" on center each way. The slab is shown over 2" of rigid insulation over a compacted gravel base course . The exterior walls are not bearing walls and they are constructed with double spaced sill plate . The plates are spaced 1.112" clear to create a slip joint so as to allow the slab some freedom to move vertically relative to the embedded posts. It is my professional opinion that the noted agricultural building is professionally constructed with significant structural integrity, and can safely resist the noted design snow loads and a design wind load based upon a wind speed= 90 MPH (3 second gusts). Sincerely, Kurtz & Associates, Inc . Brian Kurtz , P. E.