Many buildings simply are not built squarely, or they have “settled” over the years and are no longer square. Due to the strong horizontal and/or vertical lines of metal roofing, it can be very obvious when it is installed on roofs that are not square.
The first step, before starting any roof installation, is to check it for squareness by taking horizontal and vertical measurements at various locations and by making sure that all corners are 90 degrees. When it is determined that the roof is not square, you must look for special application procedures that will help to minimize the obviousness of the problem. In all cases, the property owners should be informed immediately of the problem and should give their approval to what you want to do to remedy the situation. In some cases, the roof structure can be repaired. However, if the metal roof must be installed over the affected roof areas, check with the product manufacturer for suggestions. In most cases, the appearance of the problem can be minimized by using a special starter detail that allows you to ensure that the first course of shingles is parallel to the ridge and plumb to the gables.