Too many replacement windows are being installed without regard to code-required proper anchor size and spacing
A problem largely ignored in the annual installation of the 25+ million replacement windows is proper sizing and spacing of the anchors according to a recent poll conducted by AWDI. Every replacement window is defined by performance characteristics obtained in laboratory testing procedures per NFRC, AAMA and others. These results were achieved with the test sample anchored to the test buck, and those anchor sizes and spacings are attached to every test report. These sizes and spacings are extremely important to duplicate the lab performance in the home. In fact, building codes demand that the window or door unit “fastener size and spacing be provided in instructions and that they shall be calculated based on maximum loads and spacing used in tests.”(ICC Code 1405.13.1)
This omittance occurs because of the arm’s-length relationship between manufacturers, dealers and installers when it comes to all instructions, not just anchoring. A few of the bigger companies are publishing the proper spacing and anchor size. But the majority don’t. This requirement is missing from ASTM-2112, as well. If the in-service performance is to match the tested performance, and liability for problems with the in-service performance is to be avoided, then windows need to be anchored to match their testing circumstances.
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