I built four French screen doors a few years ago to enclose an open
lanai. I left an uncaulked 1/4" gap at the bottom of the jambs. Do
you have any idea how many different types of critters can get through
a 1/4" gap??? The cats liked the gap, wife didn't, no more gap

As DPB mentioned, you should always leave a gap at the bottom for moisture
to escape. However, 1/4" is a huge gap, the gap should be 1/16" or so.
Enough for moisture to get out, but not enough for bugs to get in.

Anthony Watson
www.mountainsoftware.com
www.watsondiy.com