In article , "Pete C"
says...
On Thu, 27 Jan 2005 19:01:17 -0000, "andrewpreece"
wrote:

Either your house is moving, or your door is absorbing moisture. Since it
happens in winter, I guess that fingers the moisture theory. Plane your door
so it fits and then paint it gloss on every surface, including the
underside. This ought to stop any more moisture ingress.

Epoxy would be less likely to rub off, and some graphite added will
make it more slippery.

Furniture wax worked okay on my garden gate.