Most windows used to be made of wood because it is known to be very stable. Windows made from wood seemed to last for long and did not distort fast. Things have changed, and in the current world, most windows are made of vinyl. Compared to wood, vinyl windows is not very stable. Heating and cooling lead to contraction and expansion of the material hence easy distortion. To prove this leave a piece of vinyl in the sun and see what happens to it. It is for this reason that the windows should be held firmly when fitting. They should not be held very firm, however. Room for expansion and contraction should be left. Otherwise, the window will easily distort. Space and movement allow the vinyl to get back to its original position and shape.
If during a fitting, for example, space is not left in the corners or the window is made to perfectly fit in the space provided, vinyl will expand, and due to lack of space, it will bend to allow expansion hence distortion. Such can even break the glass. The opposite will too cause problems.
So many installations are made without shims to restrain the window. Most installations are made by attaching the nailing fin only. In most cases, the method has been found inadequate and very harmful to the window. If the fin is damaged during transport, nailing it is useless, the window will be held temporarily. Without proper support and restriction, the window distorts based on loads or pressure placed on it. It sags in the middle if supported on the corners. If supported at the center only, then it sags on the corners.
If the window does not remain square for five years or even a year after installation, it means that it was not appropriately and correctly installed. Make sure to get a qualified and experienced person when fitting vinyl windows.…