how important is a door pan?

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Old 09-17-07, 06:07 AM
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how important is a door pan?

I am installing an 8' set of French Doors on my second floor, exiting out to a walking deck. There is about 3" between the outside deck surface and the subfloor.

No issue about snow or standing water, however there might be an issue with wind driven water and any flashing is over the lip of the subfloor. So I am wondering if a full door pan is really necessary.

Also, would I put the pan down then level the door or do the leveling then put the pan.

There was mention in a prior post about a generic door pan that could be assembled but I couldn't find it. This would be a better solution than me trying to make one out of galvanized flashing.
 
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Old 09-17-07, 05:08 PM
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Doesn't cost a lot and only takes a few minutes more to install, why not!!! You never know what will happen in the next 20 yrs or so. When the 100 yr storm comes, you won't have to worry that you didn't install the pan.
 
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Old 09-17-07, 06:12 PM
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I agree with Just Bill that it's cheap insurance. I usually make my own out of aluminum trim coil. In all honesty, I also have installed a lot of doors where I felt it just wasn't necessary.

You mentioned one thing, however that would lead me to highly recommend it. The deck. When I install new doors on existing decks, the bottom of the rough openings are usually in pretty bad shape, because of water that has blown back underneath the old door. Housewrap is usually non-existant and deck ledgers are usually not flashed. When you replace the door, it's a good time to fix some of these items.

Once the door is out, I'd recommend removing the deck board that runs along the house so as to expose the ledger. If there is not a flashing over the top of the ledger, install one. That's first. The top lip of the ledger flashing should then be covered by the front lip of the pan flashing. (It's usually easier to install the pan flashing on the flat subfloor, even if it's out of level. A bead of caulking under the pan flashing will prevent air infiltration underneath it. Shims can be laid on top of it to level the door later. A large bead of sealant on the interior edge of the pan flashing would prevent air infiltration under the door.)

If you don't want to buy a pan flashing or can't find one, the next best thing would be to flash the bottom of the rough opening with some butyl rubber "peel and stick" membrane flashing (Tyvek StraightFlash, Grace Vycor Plus, Protecto-Wrap, etc). These are usually available in small rolls that are about 6" wide and 25' long in big box stores. You'd cut a piece about 6" longer than the rough opening is wide. You'd fold 3" of it up onto the studs on each side and slit it so that it will fold into the corners. You'd want about 3/4" to fold up vertically onto the interior side of the rough opening (vertically onto the edge of your finished interior floor), and let the rest of the outer flap fold over the top lip of the ledger flashing. You'd then cut a couple small 4x6 pieces and tape bottom corners of the rough opening again (going around the bottom of the studs and around the corner onto the sheathing), to cover up those vertical slits you made.

Pretty easy to do, saves you the trouble of finding and buying a pan flashing... AND... it's better than nothing!

When you go to reinstall the deck board that you took off, you might want to make sure that it's not tight to the house, and that there are some kerfs cut in the bottom to allow any water coming from the pan flashing / ledger flashing to escape. I like to leave a little gap along the house to promote drainage / drying as well.

After the door is installed, if you decide to caulk the front edge of the threshold, you would really only want to caulk the very front edge where it meets the deck board and be sure that you are not injecting it and creating a dam with your caulking that would actually prevent water that gets under the door from escaping. The bead of sealant on the interior edge of your pan flashing (or butyl tape flashing) is your primary seal. If the rest of the opening is properly flashed, it will all drain to the outside anyway. Caulking in front of the threshold would be purely cosmetic.

This is pretty much the "ideal way" I'd install a door if time were of no concern. In the real world, however, most carpenters just put the door in and forget it. If it leaks, they'll be long gone by the time the damage shows up. Some of those suggestions might help you- since it's your own home and I'm sure you want to do the best job possible.
 
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Old 07-30-11, 09:34 PM
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I know this post is a few years old, but I just read it. Time for a BIG fope slap. I should have read it back then or asked before, but I thought the big box store guy set me straight. NOT. Today I opened up the porch floor (removed the Pergo, etc...) because the floor felt soft. My wife had mentioned it and I thought the Pergo had slid and buckled. NOT. The 1/2 inch underlayment AND the 3/4" sub floor is all but rotted away, and I think it was because of no flashing. (after all, the guy at the store said the patio door ( knocked down frame) was ready to go. Again: NOT. So tomorrow I'll finish ripping out about 100 Sq Ft of rotted plywood and replace it, then re-install the frames AFTER I have made some decent flashing around EACH of FIVE patio doors. I feel like Homer Simpson- DOUGH!!!
 
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Old 07-30-11, 10:03 PM
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Sorry to hear about your dilemma. Flashing tape over the nailing flanges (sides and top) will help some, but sealing the threshold is the tricky part and usually has to be done correctly when the door is originally installed. It would be nice if all doors came with an integral threshold flashing to prevent water from blowing back under the doors, but I suppose if they did that doors wouldn't rot as fast and sales would go down.

Good luck!
 
 

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