I have installed several prehung exterior steel entry doors over the
last few years, and virtually all of them have minor leaks somewhere
around the bottom. The first was the entry door to our garage, which
has now rotted and will need replacing this summer. Obviously, I
don't want any other doors to rot like the first one, or worse yet
cause structural damage to the buildings.

I've tried to follow the best building practices I can, wrapping the
wall felt into the door opening, applying flashing tape around the
opening (bottom, sides, then top), caulking with high quality PL
polyurethane caulking, etc. The exterior door frame is completely
sealed and there's no possible way water is coming in around the
exterior of the frame.

As far as I can tell, the water comes in somewhere around the door
sill at the bottom. I'm not positive, but I think the water runs down
the sides of the door against the weatherstripping then along the
crack between the metal sill and the the wood jambs. I've tried
caulking these joints also, which has helped, but the water is still
getting in somewhere.

Unfortunately, there's no overhanging roof to protect most of the
doors, and adding an external storm door is not an option either.

It's always advisable to first protect a doorway by
minimizing the amount of rain that affects it. Check out an affordable
solution from DOORBRIM at http://doorbrim.com.

That message is FOUR years old, and I wouldn't exactly call a $190
plastic brim "affordable". Not to mention all of the sample photos show
commercial installations, not real attractive for residential use.

Also, the brim also wouldn't do anything to prevent water from splashing
back up from the decks or sidewalks. My in-laws have a roof overhanging
their front door, but their door frame is rotting at the bottom from
splashback just like mine did.

In any case, I solved the problem by replacing the wood door frames with
composite frames that won't rot. The door itself was fine, so I simply
measured the existing door, hinge, and lock locations, then ordered a new
frame from Lowes. To protect the structure from any water that might leak
around the frame, I also installed a Jamsill tray (www.jamsill.com) in
the door opening before installing the new door frame.

I haven't had any problems since then and the total cost was less than
the "brim".

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