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COVER S"I'OIZY <br />in the design stage. 'T'hroughout the <br />process, I have been able to provide con- <br />struction support through achlal contract- <br />ing or consulting for most of the projects. <br />One of the most recent projects was <br />Ledford High School, designed by Bilger, <br />and constructed by LaFave's Construction <br />Company of Landis, N.C. LaFave's had <br />previously completed approximately <br />103,000 square feet of metal retrofit t•oof at <br />\Nest Senior High School, and is currently <br />performing the same type of work at Hasty <br />Elementary School, both a part of the <br />Davidson County School District. "The <br />Ledford project was bid in August 2004, <br />started in the last quarter of that year, and <br />finished in October 2005. It is almost <br />113,000 square feet and covers a flat, <br />smooth-surface BUR and a graveled BUR. <br />This project had the same basic design <br />concepts utilised 16 years prior to perma- <br />^ently soh~e the leaking flat roof problem. <br />Some of the basics of this design are as fol- <br />lows: <br />A base clip is attached to the existing <br />structural system, without removing the <br />existing roof system. This is accomplished <br />by placing the base clip on the existing <br />roof and installing a long fastener into the <br />building's structural members. Bilger ana- <br />lyzed these members for their structural <br />capacity under the loads introduced by the <br />new retrofit framing system to determine <br />their adequacy to accomm~odate those <br />loads. Then the ftstening mate--ials and <br />quantities necessary to resist the design <br />wind loads were determined. <br />A variable height 16-gauge channel was <br />then attached to the base dip. T7ie height <br />of this post was calculated to produce a <br />minimal positive roof slope. In the case of <br />Ledford High School, a minimum slope of <br />3/8 inches per foot was chosen. While this <br />slope is relatively flat, when a hard surface <br />like a metal roof panel was used for the <br />weathering surface, water is allowed to flow <br />freely to the building perimeter instead of <br />ponding on the roof membrane. This fact, <br />positive drainage, is the simple but most <br />potent characteristic of a metal retrofit <br />roof system that provides the greatest <br />changes in the roof component of the <br />building. <br />A metal "Z" purlin was attached to the <br />top of the variable height posts. After <br />installation, this purlin system a•eated a <br />__ Page 163 of 199 <br />AIE'1'Al. ROOFI\C. i rG13RUARY/MARCH 2006 - 23 <br />