Determine If Your Windows Are Square
At SpencerWorks our window is designed to fit and work best when installed with the proper 1/16″ space. Windows can be tuned to match out of square openings for the best appearance and performance. Before measuring, scrape and remove any paint build-up on your blind stops, exterior casing and sills. Stops, casing and sills should be free of any accumulated materials that will hinder the performance of your new storm window.
Step 1. Measure the distance diagonally from the corners of the blind stops and the exterior casing. If there is a difference of 1/4″ or more between these measurements you may want to tune your storm window before installation (see figure 2).
Step 2. Place a straight edge against the inside edge of the exterior side casing. Bows and humps causing gaps greater than 1/2″ between the straight edge and the exterior casing may require the storm window to be tuned before installation. If your window exceeds the above tolerances, you may wish to order your storms oversize. Oversize storms can be trimmed to fit with the optimal 1/16″ space on each side.
NOTE: Trimming storm windows to exactly match an out of true opening requires a moderate amount of woodworking skill. While this is possible for an amateur with proper tools, it is advised that a carpenter be hired to trim the window. If your windows come painted, you will need to prime and paint those areas that have been trimmed.