Another mistake made is allowing a contractor to install new construction windows and patio doors vs. replacement windows and patio doors. New construction windows and patio doors are only supposed to be used when a brand-new home or a new addition to a home is being built. Since the studs of the home are exposed the window can be installed directly on to the frame by use of a nail fin frame, which means it is nailed into the framing of the home.
Beware of contractors who want to remove the stucco or siding and replace your windows and patio doors with cheap off the shelf products bought at one of the big box stores. These are usually builder grade windows and not the best option. This type of installation leads to potential leaks and though they look new, they usually fail within a few years since these stores usually sell on quantity not quality.
The best option is using a Replacement Window or Patio Door. Replacement windows (also referred to as retrofit windows) have been developed so a contractor does not have to remove the exterior materials of the home to install the window or patio door, they are measured to fit in the existing window or patio door opening and will only replace the actual window or patio door.