Housing Giants - September 24, 2008 - (Page 18)

Process is an important factor, as wet or dry conditions can significantly change the timing of when you stress the tendons.” Grisolia, with almost a decade of experience in the home building industry, has assisted housing giants affected by quality issues like cracking in posttension slabs in southwest markets. othEr Errors that caUsE crackING Tendons not supported properly Concrete overworked during placement Tendons transitioned poorly around slab penetrations sheet should be level and the slip sheet should fully cover the foundation footprint. All seams in the slip sheet should overlap at least 12 inches and be sealed with 3 inches of construction tape. In addition, the slip sheet should be on top of the gravel layer, so the sheet is directly underneath the slab. Error No. 3: INcorrEct INstallatIoN of thE slIp shEEt The slip sheet (10 mil polyethylene) reduces the friction between the slab and bearing surface, allowing the stressing operation to move the slab smoothly across the ground. When the slip sheet is installed incorrectly, such as beneath the gravel layer or on top of an uneven surface, the slab resists movement, preventing the stressing operation from closing any cracks that opened up during curing. Anthony Grisolia cautions housing giants: “When the slip sheet is missing altogether or not directly under the slab, it significantly increases the need to exert extra force on the tendons in order to counteract the additional friction. As a result, you increase the likelihood for ruptured tendons.” To prevent this issue from occurring, the bearing surface beneath the slip What’s thE lEssoN lEarNEd? When all is said and done, post-tension slabs aren’t as quick and easy to construct as traditional slabs. But when construction teams properly understand and follow the procedures set forth for post-tensioning a slab, they’re adding to a foundation’s lifespan and helping you hold onto your hard-fought income. HG Michael Dickens is the CEO of BuildIQ, which provides online information, tools and training in home building best practices to help builders take their homes and businesses to the next level of quality and performance. 18 hoUsING GIaNts.9.24.08 WWW.hoUsINGGIaNts.com http://homebuildingqc.ibacos.com/risk-control.aspx http://www.housinggiants.com

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Housing Giants - September 24, 2008

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