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.

The way I've fixed mine is...

I originally posted about the rotting door frames about three years ago.
In almost every case, water ran down the sides of the door jambs, and
wicked up the bottoms of the jambs. This quickly caused the door jambs to
rot.

My solution was two fold:

1. I replaced the door frames with composite frames (PVC material like
Trex decking). I just measured the door and hinge locations to the
nearest 1/32", and ordered them from the local Lowes store. The steel
doors were fine, so no reason to replace those. The old doors and hinges
attached to the new frames with no difficulty.

2. Once I had the old frame out, I repaired a couple of minor rotting
areas in the sheathing beneath the door. Then I installed PVC "Jamb
Sill" (www.jamsill.com) trays in the door opening before reinstalling the
new door frames.

Finally, I caulked around the door jambs as I would do in any normal
installation. The composite frames should be more resistant to rot, and
shouldn't wick moisture like the old frames. The Jambsill tray ensures
any water that finds it's way in will exit out the bottom and not cause
damage to the building structure.

I don't recall the exact prices now, but I think the cost per door was
less than $150. Not cheap, but it was a small price to pay to ensure a
long lasting installation.

Obviously, it would have been smarter to use composite frames and jamb
sill trays during the initial construction, but I didn't know about them
back then. Still, it only took a couple of hours to replace each door
frame.

Other than the cost, the only downside is painting the composite PVC
trim. I had to apply primer and about three coats of paint for adequate
coverage, but three years later it still looks great.

Anthony Watson
Mountain Software
www.mountain-software.com/about.htm