Signs of light reflecting through at the doorsill or jambs suggest that the door is not fit as well as it should be. Sunny days will reflect more light than cloudy days. Interior Doors Interior doors are often hollow core or builders line quality. Exterior doors are built and glued for exterior use. It is important that interior doors not be used for exterior applications.
Interior doors have a tendency to delaminate when exposed to exterior elements.
Delamination of an interior door is typically caused by moisture, however, poor manufacturing may be the cause in some cases.