08-20-07 Agenda Item 2A, City Hall Repair Update

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ARDEN HILLS CITY HALL BUILDING City Council Work Session on 20 August 2007 1245 West Highway 96 Arden Hills, Minnesota INTRODUCTION This document presents factual information, opinions, aud costs to be used during a City Council work session to be held at 5:00 p.m. on 20 August 2007 at the Arden Hills City Hall building located at 1245 West Highway 96 in Arden Hills, Minnesota. BACKGROUND An investigation was performed by Wiss, Janney, Elstner Associates, Inc. (WJE) in 2006 aud included a review of available documents, a limited visual condition survey of the interior aud exterior sides of exterior walls, inspection of as-built conditions at inspection openings, water testing of exterior masonry walls and windows, aud preparation of a final report dated 22 February 2006, with opinions and recommendations. Repair specifications and drawings for recladding the chimney, dated 17 February 2007, were also prepared by WJE. The chimney recladding work was completed this summer by Building Restoration Corporation (BRC). Subsequent to the recladding work by BRC, BRC cut additional inspection openings in the exterior masonry walls for City personnel and WJE to observe the condition of the relieving augles. The following summarizes the results of the investigation performed by WJE in 2006: I. As demonstrated by testing, water intrusion occurring along the south foundation wall is due to defects in the through-wall flashing system installed at the base of the wall. These defects permit water which collects within the wall drainage cavity to bypass the through-wall flashing and migrate into the occupied spaces below. Presently, water intrusion to the lower level has been identified at two locations: at one location on the east foundation wall, and at another location at the east end of the south foundation waiL 2. The cause of past water leakage through the north facing wall located above the main level conference room is unclear. Potential causes of the leakage are water penetrating the joints in the coping stones, in combination with improper flashing at the top of the wall, and water entering the wall cavity through improperly lapped felt paper. Leakage through the flashing which was installed in 2005 by BRC does not appear to be a cause. No recent leakage has been observed at this location. 3. Deficiencies exist in the through-wall flashing above the windows on the south elevation of the building. Defects include the absence of proper end dams in the flashing, poor adhesion of the flashing to the steel surface at terminations, discontinuities of the steel sunscreen bracket plates, unsealed penetrations through the building paper, and the flashing terminating short of the exterior face of the waiL Surface corrosion was observed on the steel under the membraue flashing, indicating water has bypassed the membraue flashing in the past.