This can happen for several reasons, but it is often due to the door being anchored improperly Many different types of patio door frames that leak water at the bottom corner should be siliconed over top of the foam pad gasket at the frame corner to ensure water cannot get past this junction. Whether it be identifying or fixing the problem, let’s take a look at what you should do when water enters through your door threshold.
Water Background Images - Wallpaper Cave
Another effective way to stop water from leaking indoors through the bottom of the door is by installing weatherstripping underneath it
One of the easiest and fastest ways to gasket under your door is by installing a door sweep.
A portion of wooden seals (in basement) just beneath the patio door is rotted.