b'Installing ReplacementBox FrameSliding Windows The basics for installing a sliding window are not verydifferent from the double hung. Head expanders andsill supports can be used for many sliders exactly asthey are used for double hung windows.Again, it is imperative to be sure the old frame is still properly integrated with the water managementsystem of the wall, otherwise it would be better to use a frame out installation described elsewhere inthis manual. The key to success, either way, is adequate support under the sill to avoid sagging. The most importantThere are two very important considerations when aspect of properinstalling sliding windows: installation of a slidingwindow is to have a 1. The Sill Must Be Level - and Supported!.level sillJust as it is important not to bow-in the sides of thedouble hung window, the lower and upper frame ofthe slider cannot be bowed.Check the level of the sill. Read the section in thisbook on Level and Square. The part of the openingwhere the sliding window will rest must be flat. If it is crowned or concave, then the track on which the operating sash will glide or roll, will not If the sill is crowned or allow the operating sash to close properly, and the concave, place a piece of interlock between the two or three sash of a slider 1/8 - 1/4 waterproof will not engage properly and there will be air and plywood, cut to the properpossible water leaks. length and width, on thesill and make level,Big Sliders, with multiple moving sash and heavy to support theglazing are prone to sag in the middle if notsliding windowproperly supported in retrofit applications. If the sillcant be assured of being level and strong, it would be wise to install a piece of exterior grade plywoodalong the bottom of the opening to ensure that it isflat in Frame-In applications, and fastening a water-proof board along the sill to stiffen the tracks forFrame-Out installations. Just shimming the bottomof the window is often not sufficient to level the trackbecause the weight of the operating sash can deformthe track if the support of the under sill is not uni- Properly insulateform (flat) and supported. the perimeter ofthe window frame.Shimming the window underneath the track maytemporarily solve the issue but over time, only astructural addition of something akin to plywood,Sill Suport will assure proper operation and weather tightness (If sill is sloped)necessary for a sliding window.Window Fitters Guide to Window Installation57 2020 AWDI, LLC Do not reproduce without permission'