how to temporarily waterproof a gap

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Old 05-20-16, 05:42 PM
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how to temporarily waterproof a gap

Hi
Have house with shingle siding and a deck.
There is a gap of say 1" between the bottom of the shingles and the deck surface. See pic.
There is flashing but the flashing is short and does not extend up behind the shingles so I think water is getting behind the flashing and into the wall.
I would like to fill the 1" gap with a temporary waterproof something to test the hypothesis that water is getting behind the flashing.
What would be a good temporary material? I even thought of just cramming a piece of garden hose into the crack; but that is kinda crude.
Thank you
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Old 05-20-16, 05:52 PM
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Garden hose isn't a bad idea; but not sure if you could count on it sealing very well. You could line the area with a cheap disposable drop cloth and then fill the gap with can foam. Foam backer rod would be another idea. It comes in 1 inch but might be hard to find.

But if you're getting water inside and think it's coming from there, you ought to be able to hit it with a hose and see water get in....
 
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Old 05-20-16, 06:17 PM
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There should actually be two layers of shingles and i suspect the flashing you think is short is actually disappearing under that second layer, referred to as the first course of shingles.

A ledger board and the related flashing are extremely important and MUST be installed correctly or the rim joist will be rotted out in just a few years. You need to determine how that was flashed.

Easier said than done.

Bud
 
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Old 05-21-16, 07:12 AM
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Those shingles never should have been that close to the decking, the deck boards should not have been tight to the wall like that.
Those gaps between the shingles is way to wide.
As mentioned there should have been two courses at the bottom with the second course covering the gaps below.
With the shingles that close to the decking the splash back is going to rot them out.
I would have used a piece of flashing out over the rim joist and up the wall at least 6", waterproofed the wall with something like storm and ice shield 24" up the wall, then used a piece of 1 X PVC lumber, Z molding, window tape (or slip the house wrap over the top of the Z molding) then a kick out strip, (I use vinyl or pressure treated lattice) then install the shingles.
 
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Old 05-21-16, 05:19 PM
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how to temporarily waterproof a gap

Reply to those below (remembering I am not a builder)

There are two layers of shingles, I can see ‘em.

The top edge of the flashing is not disappearing under the second. I can see and feel the top edge of the flashing ( not everywhere but in certain areas along the decking ).

How flashed? Here is a link to my drawing. How do I know? By peering with a flashlight and feeling round.
deck flashing - engrav

in the spot of interest the flashing does not extend up behind the shingles.

Shingles too low? There is in one place splash back rot proves the point.

Question remains
Short of rebuilding the thing and
Since the problem is localized to one point along the deck (not the entire length of the deck)

What would be good temporary material to fill the gap, keep water out?

How about closed cell backer rod?
 
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Old 05-21-16, 07:52 PM
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If there was two layers of shingle you would not be seeing the smooth area between the shingles and no way should you be seeing the flashing behind the shingles.
That z molding you can see on top of the decking is nice but not enough to prevent damage to the house and will always leak no matter what sealer you use.
Main reason why most of us suggest free standing decks with no ledger.
 
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Old 05-21-16, 08:14 PM
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Joe... never seen a piece of lap siding used as a starter row?

You should be flashing the top edge of the ledger flashing...prying the siding out just enough to slip another metal flashing up under the siding. With the small amount of clearance, you will likely need to either remove that first deck board or trim the top leg of the new flashing with tin snips.
 
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Old 05-21-16, 08:56 PM
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how to temporarily waterproof a gap

see new drawing and the green line

deck flashing - engrav

so I should wedge a new piece of flashing in there like shown with the green line?
 
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Old 05-21-16, 09:23 PM
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Yep.............................................
 
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Old 05-21-16, 09:28 PM
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how to temporarily waterproof a gap

Ok

have now read about "flexible" flashing membranes
might be easier to squeeze in there

any opinions about "flexible" flashing membranes?
 
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Old 05-21-16, 09:33 PM
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You will never get it under the siding... they are sticky. Buy a z-flashing and trim it as needed.
 
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Old 05-21-16, 09:41 PM
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ok, got it
next query
say the area in question is 4' long
can I use four 12" pieces (actually longer for overlap)
or must it be one continuous piece
 
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Old 05-21-16, 09:51 PM
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If it's temporary, sure. But it means you will have a double thickness of metal where they overlap. So if you barely have enough clearance to slip just one piece of metal in, it would be better to use ONE 4 ft piece so as to avoid the extra thickness. If you can pry the siding loose to open up the gap it will make your life easier.
 
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Old 05-21-16, 10:02 PM
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got it, thank you for responses

assuming I get it in, does it need caulk, adhesive, or anything?
 
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Old 05-22-16, 06:22 AM
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Just to add another wrinkle (pun intended) for when you finish this off with something permanent, but two pieces of metal tight together as shown in your pictures will wick water from the bottom right up to the top of the existing flashing. Google capillary break for metal roofing.

I doubt it would provide a flood of water, but over the long term the wood at the top of the junction will suffer.

Bud
 
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Old 05-24-16, 03:35 PM
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how to temporarily waterproof a gap

Hi
I continue exploring this matter. Thanks for the comments.

During a serious rainstorm, if the deck flashing and all is working properly, will water be running down the face of the ledger board and the sides of the joists?
 
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Old 05-24-16, 05:58 PM
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Yes. But it shouldn't get wet on the back side of the ledger that is attached to (facing) the house... that's the whole purpose of the ledger flashing. The face of the ledger and the joists will obviously get wet when it rains.
 
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Old 05-24-16, 07:08 PM
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thanks, got it
will continue the exploration
 
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