Source: REPLACEMENT CONTRACTOR Magazine
Publication date: January 1, 2006
By Martin Halladay
Comparing installation instructions from different vinyl window manufacturers reveals a jumble of contradictions. Here are some of the most striking examples:
Should the sill be shimmed? Several manufacturers' instructions recommend shimming between the rough sill and the window frame in two or three locations, just as with wood windows. Others recommend that their windows be installed on a continuous, level rough sill. One manufacturer introduces a third option, instructing the installer to use shims as with a wood window, then to remove the shims after nailing fins are fastened — leaving the window hanging by the nailing fins.
Should the fasteners be driven home or left proud? The instructions from one manufacturer recommend leaving the fasteners proud because this will not restrict the window from expanding and contracting. Installers of another window brand, on the other hand, are instructed to use roofing nails driven all the way in.
Should the nailing fin at the head of the window be left unfastened? Some manufacturers recommend fastening the nailing fin at the head of the window, while others warn against the practice. Some installers avoid the problem by driving a nail above the fin, then bending it down to pinch the fin. This procedure is also part of some companies' installation instructions.
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