Window Fitters Guide to Window Installation 7 ©2022 AWDI, LLC Do not reproduce without permission Shimming is necessary for almost every window and door installation - mostly because there is no such thing as a perfectly square and plumb opening. Shimming allows you to center the window and level and plumb the window in the opening. Shimming is also one of the more misunderstood, and/or carelessly attended to steps in installation. Very few installers bring adequate shimming to the job with them and the installation is the worse for it. There are two keys to proper shimming 1. Shims must be between the window unit and the rough opening at each spot where the anchor screws are placed, and the screws should pass through the shims in order to keep them from shifting in the opening, and to ensure that the win- dow frame is secure and snug to the rough opening 2. Shimming must be flat. Using tapered shims alone will result in the distorting of the window frame which will not only keep the frame from being adequately secured to the rough opening, but will probably cause the distorted frame to either impede the operation of the window or door unit, or cause the precision balances or weatherstripping to fail to work properly or wear out prematurely. If the window unit is not fitted with factory installed butterfly clips or flat plastic shims are not available, tapered shims are best used in pairs. In this method, the first shim is placed fat side in, the second is slid in thin side first until the pair makes a flat, and snug fit. Then the shim pair is trimmed flush to the outer edge of the window frame. Since windows with fins or replacement windows fitted against the old window stops prevent shims from passing through to extend on both sides, it becomes tricky to install them properly. With available shim stock, precuts are usually 12 inches long, 1-1/2 wide and taper from 5/16” at the fat end to nothing at the other end. Two Solutions Plastic, Stackable Shims Horseshoe or “u” shaped shims work perfectly because the open portion goes over the anchor screw and because they come in differ- ent thicknesses, and are stackable (small grooves lock them in a pile as more are added), shims can be added and removed as the window is leveled, plumbed and squared. Self Shimming Anchors. Developed in Europe these anchors have a collar set just below the head so that the anchor “snaps” into the hollow lineal holding the lineal’s wall between the collar and the head. In this way, as the anchor is turned clock- wise, the frame is pulled closer to the opening wall. When the anchor is turned counter-clockwise, the frame is pulled away from the opening wall. The result is dynamic shim- ming during installation and after. With Self Shimming anchors, final adjustments can be made after all trim is added allowing precision alignment of the locks, interlock and weatherstripping. Self Shimming anchors can come with plugs for use in concrete walls to meet Hurricane Codes. Details of Proper Shimming Tapered Shims in Pairs create "level" support After inserting shim pairs cut off the ends flush with window frame SAMPLE MANUAL
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