In the past, most windows were made of wood, which is a very stable material. Today however, the most common material for windows is vinyl, which is not nearly as stable as wood. Vinyl is very affected by weather conditions, expanding and contracting with the rising and falling temperatures which cause them to be distorted. The fragile nature of vinyl windows makes it imperative to hold the windows in place with mild pressure. There must be the right amount of room for the vinyl to expand with the temperature changes but also be able to go back to its original shape, which is why the amount of pressure applied is very important.
If the vinyl windows are made to fit the hole with precision, then there would be no room for expanding which would cause the window to distort. The same is true if we were to put solid blockings in all of the corners to assure a secure fit, there would not be enough room for the window to change. With vinyl windows, they will expand with or without an allowance for it. If we don’t leave room, then we risk the chance of the window possibly bowing, twisting or even shattering.
The latest technique to install vinyl windows is only by attaching the nail fin. This procedure which is widely practiced has been shown to be inadequate and possibly harmful to your windows. The nailing fin is simply a thin piece of vinyl that projects out of all four sides of the window. To install the windows, nails are driven through the fin into the wall framing around the window. The problem with this installation lies in the fact that if the hole isn’t perfectly sized or the rough opening isn’t square, the framing will not be behind the fin everywhere, putting your windows at risk. Another problem with this type of installation is that if the nailing fin is damaged before installing it is basically useless. This technique to install vinyl windows is a temporary solution.
In order to rectify this situation, sometimes scrap blocks are used to support the window off the rough sill. The problem with this is that the blocks are usually incorrectly placed which causes further distortion to your windows. Improperly supported or restrained windows will quickly distort depending on the pressure that is put upon them. Depending on where the windows are incorrectly supported depends on how the window will react. Windows supported only in the corners will sag in the middle and windows only supported in the middle will sag in the corners. The result is having the bottom of your window resembling a roller coaster.
If your vinyl windows are improperly installed, you could notice distortion and damage as short as one year after installation. I have personally inspected many installations and a large majority was done incorrectly. Many of the windows I inspected had problems within the first year of installation.