Exterior door flashing (how to)

Old 05-14-12, 06:33 PM
Thread Starter
Join Date: Jan 2012
Location: Canada
Posts: 2,511
Received 21 Upvotes on 18 Posts
Exterior door flashing (how to)

The previous owner had installed a third rear door that lines up with the basement stairs. The door was a good idea, but they didn't finish the flashing around the door.
Below is what I am working with. What is the best method of finishing this knowing it will see rain and snow?
Name:  IMGP0026.jpg
Views: 15178
Size:  17.4 KB

Name:  IMGP0027.jpg
Views: 29937
Size:  23.3 KB

Name:  IMGP0028.jpg
Views: 20823
Size:  24.0 KB
Old 05-14-12, 07:38 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Posts: 27,242
Received 1,958 Upvotes on 1,755 Posts
Sheesh. what a nightmare.

Well not to change the subject, but number one, I would check to see if there is a flashing on that deck ledger. If there isn't, it's going to rot the wall out behind the ledger and someday the whole thing will probably give way when you least expect it. If it's concrete behind the ledger and the deck is free standing then it probably doesn't need any flashing.

Fixing that would probably be number one, since the flashing will have to extend under whatever you will be doing underneath your door sill.

I'd be tempted to remove all the exterior trim he put up and start over. Usually you want to trim the door out so that someone can put a storm door on, and it is pretty obvious that the door trim is in no way put on in the right manner to accept a storm door someday. So that's another reason to rip it off.

You can order a sill extension to clip into that slot on the front of the aluminum sill, and I would highly recommend you do that. Order the widest one they have available. This will extend the aluminum out farther like it should have been in the first place.

After it is installed, you would want to put window and door flashing tape all around the perimeter of the door... it will be applied at the same level as your sheathing, which "should" be visible once you remove all the exterior trim. Tape the bottom first, making sure the top edge of the tape seals to the bottom of the aluminum threshold. The rest of the tape can overlap onto the exterior jamb slightly (3/8" or so).

If that is vinyl siding, you might want to slip a j-channel behind the siding on the right side and top. You might also want a drip cap flashing on top... not sure if you will have to remove any siding to do that or not.

Personally, I would probably want the face of the new exterior trim to be furred out so that it would come about half way out on the j-channel. So I'd pad the wall out with some furring that has been ripped to the right thickness. I'd extend the exterior side of the door jamb out as well, to this same level. It will sit on top of the nice aluminum threshold extension that you put on. To extend the exterior door jamb, the best thing IMO, is to use 6/4" Azek (ATM), which is a PVC trim. (never rots) but it's kind of hard to find. It's nice to use something that's about 1 1/4" thick, because your face trim has to be set back 1/2" from the interior perimeter to allow for the storm door z-bar.

When you put your exterior trim on, try and leave an opening that is roughly 36x81 (or 32x81, depending) for the storm door. The face trim also needs to be a full 1" thick to allow for the storm door z-bar thickness.

Underneath the aluminum threshold extension, just rip yourself a piece of trim to fit there (again I'd use the pvc Azek) so as to cover up your deck ledger flashing, and any furring that you've added to keep that apron from appearing recessed. Whatever you add under the door needs to be solidly affixed, because when people step on that sill it needs to be solid.

When installing Azek, "Split Stop" screws work really well. They leave a big hole to fill, but filler and paint will make them disappear. Whoever removes it someday will hate you, but the trim will be nice and solid.

If you wanted to try your hand at renting a metal break and bending some aluminum trim coil to cap your exterior trim, that would be an option too (instead of Azek) but most of the other advice would still apply... you'd just cover all the new wood that you have just used as exterior trim with the aluminum trim coil as your final step.
Old 05-15-12, 04:47 AM
Thread Starter
Join Date: Jan 2012
Location: Canada
Posts: 2,511
Received 21 Upvotes on 18 Posts
Holy information overload XSleeper.

Thank you for all that information. Feel like I am back in school as I'll have to re-read your post and take notes.

The deck is not attached to the house as far as I can see. Looks like it was a throw together. It does however line up with the poured concrete foundation, so flashing there may not be an issue.

The only other thing I may consider is not adding the storm door. This is really only a utility door used to haul stuff down stairs. There is another door ~15' to the East (right) of this door that leads into the house and the basement is accessable from within the house.

As for the poor guy that will have to remove this... It'll be me or who ever buys the house when the kids move me into an old age home many years from now. After moving during the winter (with 2 young boys), I am done.

I'll try to snap a few close up pictures as to give a better idea of what I am working with. It was getting late (dark) when I got home from the office so I was short on time.

Thanks again for the large amount of info.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: