I am replacing the front and back doors at the shore house with fiberglass doors. The front door was an available 32" size. And it was a later constructed front porch that was relatively square. Even though I bought a pre-hung, I was able to simply remove the new door & hinges from the frame and mount it in the existing frame. An easy project, did that one a while ago.
The back door is an old wooden door that is 30" wide. I found out 30" fiberglass doors are special order and REAL expensive, like $700 expensive! No thanks. And I am locked into that width because the doorway is squeezed between the end run of kitchen cab's and the wall / doorway for the bathroom. However after watching CL for a while I found a 30" door on sale for $75....couldn't be true, right?! But it was true and I wasn't beaten to the deal for a change! However, the current doorway is on the original part of the old house and is not standard height, I needed to cut down the door to 77-5/8". Doorway height is limited by the porch roof on the outside so I cant gut and cut to make the new doorframe fit.
So cutting it down seemed to be the way to go. But trimming it gets me past the layer of wood that is the top frame for the door and down to the foam filler in the door. I painted the top with the SW exterior latex I used on both new doors. It seems to have sealed it pretty well. Any suggestions for covering/sealing the top to help it last so I get my $75 worth of use from this thing?! My next move may be to cut it down another 1/2" and cut out 1/4" of foam so I can cap it with some 1x to cover the exposed foam and support the fiberglass panels.