t1-11 z-flashing and water

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I'm working on a project to replace the bottom 20" of t1-11 type siding on my house. I cut and stained new 20" sheets (including edge staining). I cut off the bottom 20" of siding from the house. I stained the new cut edge. I slipped z-flashing under that new cut edge and nailed it in place through the siding about 1 3/4" above the cut edge (the back edge of the flashing is 2" tall). I left a 1/8" gap between the new cut edge and the flashing (so that panels are separated by 1/8"). And finally I slipped the new panels into place and nailed them in with galvanized ring shank 8d framing nails.
I finished this yesterday on a wall and then we had a massively torrential rain last night. Today I went and looked at it (this is a wall in the garage so I can see the other side of the wall too). There is dampness on the back edge of the siding just above the back edge of the z-flashing. Not everywhere but in some places. Back outside I looked at the flashing and you can see some water still sitting in the groove.
Is this normal? One thing that is true is that the existing siding is *badly* in need of new stain, so it could be wicking in above the new cut edge which I stained. But it seems most logical to me that water is sitting on the flashing and wicking up into the wood.
The flashing profile is 90 degree angles. It seems like it should be a little less so that water is encouraged to run out. I can try and bend it a little bit on subsequent walls.
Needless to say I'm disappointed. I guess one question is whether the flashing is supposed to keep the water out completely or simply provide an avenue for it to get out and evaporate?
thx
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I got another look at it tonight while it was pouring. The problem is definitely that water is sitting on the flashing and not running out on its own, thus it wicks up into the siding above it. I tried tapping down the flashing at each groove but it doesn't look like it's enough to make a big difference.
I'm thinking that on the next wall I should install the flashing with a 1/8" gap in the back and then try to bend the front down another 1/8" and then install the lower siding panel up to that front edge, so that there is a downward profile on the flashing. Thoughts?
As for the two walls I've already done...sigh. The last thing I want to do is re-do them, but we'll see. Any ideas on how to repair this without tearing it apart are appreciated.
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No ideas without tearing it apart.
I would have at _least_ 3/8" gap between the upper panel & z flashing. The bottom panel should be tight with the z flashing. Also, did you overlap your flashing strips? A 2" overlap should be minimum, with sealant applied with the overlapping pieces.
I'm not very much of a fan with the z flashing being used on siding. Ive seen too much rot, because of improper installation. I prefer to see siding overlapped by 2". I think it looks better, and does a superior job to the flashing, as long as you stagger your T1-11 so the seams are not on top of each other. Check it out on your other siding you need to do.
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Cabot wrote:

overlapped T1-11 on gables, but that requires furring out the gable, or adding another layer of sheathing up there before applying the siding, or (on new construction) actually framing the gable 5/8" (ot whatever) proud of the lower wall. But on a retrofit like this, I don't see how he would get the lower panel up under the upper panel without it looking like crap. T1-11 won't flare like horizontal wood siding. Even on gables, I have never seen a tight overlap- there was always a strip of wood up in there for the bottom nailer for the top panel, slightly thicker than the siding, so as to not provide a crack that would wick water and keep the ends of both panels wet in a heavy rain. (as well as providing an insect block.)
I'm no siding expert, but I think OP is gonna end up pulling the first two walls apart and doing it over, for a reliable cure. It is the only way to be sure, and not always be worried every time it rains.
-- aem sends...
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I've seen it done, and I've done it. Won't flare? Depends on what you call flare. I'm gonna have to take a couple of pictures and post them. Just because you've never seen something done, doesn't mean it can't be done. In fact, I'll attempt to grab a picture with where T1-11 has a 4' panel, followed by a overlapped bandboard of T1-11, followed by a full panel, followed by a gable end...... All overlapped. So flagged this thread, because it may be a couple of days b/4 I will get a picture.
Retrofit, you pull fasteners, pretty much the same way you have to do, in order to get flashing under it. It's not really difficult to figure out. Your nonsense about furring out, is just that, nonsense. T1-11 is only so thick, exactly what size fur strips would someone use to fur a 1/2" or 5/8"? Ok, maybe 3/8" lathe, but it could be so high, otherwise it will kick the siding out further than without. Think about that one. Also, you never put a trim strip at the bottom of overlapped siding, talk about a water trap! Geesh.
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Cabot wrote:

the crack (above the top edge of the lower panel), essentially a horizontal furring strip. Plywood tightly lapped over plywood in a wet environment will wick water- the overlapped part needs a gap to stay dry. I've seen plenty of t1-11 gables done exactly as I described, and with the upper panel hanging in air slightly in front of the lower panel, it dries out quickly and doesn't rot.
Post your pictures somewhere, and put a link back here. I'll look at them. But I can't see how such an installation could look decent.
-- aem sends...
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I read it again, about the "slightly thicker than the siding". Hello? This is a catch for water, I've seen plenty of rotted siding because nobody cares what happens 15 yrs down the road. I really shouldn't have to tell you, anything fastened horizontally, is going to be a water catch.Thats the problem doing something, because everyone else does it. I call BS that it doesn't rot, I've seen those jobs, which were done as new construction. Slam, bam, thank you mam, give me my money, I'm gone.

LOL, I'm not asking for your approval. I'll post a link, and I know this has been on the structure for 19 yrs, no rot, no wicking, no problems. And, is more attractive than Z strips, and eliminates the problems which come with using Z strips.
I like how you're defending the plenty of jobs done this way. LOL, kinda tells all.
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Here are some links. Its funny how people talk about insect infestation with wood, but with aluminum or vinyl siding are not worried. Insects will get behind aluminum/vinyl siding a lot easier than most wood. You make an insect block like with any other wood. The link fascia/groove detail shows how you block it, or there's a different way when installing new. But, I'm not giving out all my secrets, it took a lot of asking and looking over jobs, to see what is best against weather infiltration.
Northside
http://s132.photobucket.com/albums/q17/Roofguy/T1-11%20overlap/?action=view&current=Northside.jpg
Southside
http://s132.photobucket.com/albums/q17/Roofguy/T1-11%20overlap/?action=view&current=Southside.jpg
Band detail http://s132.photobucket.com/albums/q17/Roofguy/T1-11%20overlap/?action=view&current nddetail.jpg
Fascia / Groove detail http://s132.photobucket.com/albums/q17/Roofguy/T1-11%20overlap/?action=view&current sciagroovedetail.jpg
Rear view
http://s132.photobucket.com/albums/q17/Roofguy/T1-11%20overlap/?action=view&current=RearView.jpg
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I guess I'm missing something, but the bottom piece is protected by the downward lip of the z strip and needs no caulk. I would have run a bead of silicone caulk on top of the z strip before I pushed it up under the top panel to seal that portion of the joint.
KC
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Sealant = caulk? Or something else?
Great photos. Your install looks great.
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Thanks, that was done 19 years ago, the photos were today.
For overlapping of the Z flash, I would use gutter goop or similar, or a quality caulk.
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Cabot,
Just had our first bigtime soaker rain. Unfortunately the problem doesn't seem to be completely gone, although it's clearly a lot better than it was. Instead of the wood being soaked everywhere on the backside and up about 2-3" from the cut edge, now it's wet in an occasional spot, and not as high. I can only see about 4' of this wall from the inside before it's covered with drywall.
I went outside with a flashlight and umbrella. I don't know if I caught the worst of it, but what I did see looked like my test wall...the water was not filling the flashing gap. So I'm wondering if I should be cutting it higher (it's a bit over 3/8" gap now) or maybe just need another coat of stain on the cut edge? Because it's already up I can't stain the backside at all.
Thanks for any advice.
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I've always found it curious that even the manufacturers don't call out how big of a gap should be at the Z-flashing. I've seen it butted tight (aka siding death) and with a pretty wide range of gaps. Generally as long as the gap is large enough to get a brush in there and verify visually that the edges are getting sealed and not delaminating, that's enough of a gap. I usually install plywood siding with 1/4"+ gap...at least I did. Now I use different details to cover up the Z-flashing.
Another poster mentioned overlapping the plywood siding, and the pictures certainly look nice enough. That is a superior way to do it for maintenance as you can readily verify that the plywood edges are sealed adequately and easily reapply paint/stain. That being said, Aemijiers has a point about the flare in the siding. If the plywood siding is the structural wall sheathing, it presents problems. The flare would have gaps between the plywood and the framing and building inspectors don't like to see gaps in structural work. Siding nails don't have a lot of excess strength and deform easily. They must be pulling the sheathing tight to the framing without any gaps. It is not a big deal to remedy that, as an undercourse cedar shingle stapled/ nailed to each stud is cheap and fast enough and takes care of the taper.
As far as your situation, I hope you were careful to not nick the Z- flashing if it is the thin aluminum stuff. A score in the aluminum from a knife weakens it, and depending on the exposure, can crack with repeated expansion from temperature swings and sun.
You may want to apply a wood preservative on the cut plywood edges and apply the stain prior to installing the Z-flashing. That's the best way to insure complete coverage and prevent problems down the road. You can also pre-bend the Z-flashing a bit to provide a little slope so water won't sit on it. Since the flashing is well below eye level having dead straight flashing isn't so critical. Take it easy and bend a little bit at a time and see how it looks before installing the lower piece of siding.
R
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R, thanks for the info.
There's no question that I did cut into the z-flashing with my utility knife when trimming off the 1/4" piece. I know I didn't go through it, but it was impossible to trim that piece off without getting into it a little bit. Afterward I stained the new edge and that stain ended up filling the score marks on the flashing. I was hoping that might help.
I was definitely pre-staining the edges before I assembled. It's just that on this wall in trying to fix it after the fact that I ended up staining in the gap.
I'm wondering about the possibility of getting some oil-based primer on that edge, then staining again. ANy problem with trying that? Seem worth the trouble? I'm still trying to keep from redoing this wall.
KC suggested that water may be bouncing upward in a blowing rain. That suggests that going bigger on the gap isn't a good plan. I don't have any lumber behind this joint (except for studs) so there's nothing backing the joint that holds the back end of the flashing against the panel. Not that it flares out badly, but in a few spots it comes away a tiny bit. However, it's not like these spots are the only places with trouble.
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Sorry, stain is not a sealant. There was another guy who was working on his house and he had a tendency to get into a jamb while working on something, then ask his questions how to get out of it. I'd cringe every time I'd see his name starting a new thread. Ask your questions first and you'll get help avoiding these problems - a far cheaper and less frustrating way to go!

As long as you are taking care and paying attention while sealing the cut edges it shouldn't be a problem. It's when you get cowboy painters blowing through the job that you run into problems.

Lots of painters like the oil base primer, but I'm a fan of a wood preservative (long as it's not Thompson's). Let it dry and you won't have adhesion problems whether you decide to oil prime or just stain.

The surface tension of water, and the wicking action of wood is what kills the end grain. In a rain with little or no wind your siding will get plenty wet and the water will run down until it hits the bottom edge of the plywood. Before the water droplets take that death defying leap off of the edge, they look for an easier way down due to surface tension. They'll run back along that cut edge and if there are any unsealed voids the end grain will suck up the water. Water doesn't have to bounce up onto the underside.
Not having any blocking behind the flashing is tough. It sounds like you've been doing your homework, so I'm sure you've run across the APA 303 specs with the nifty little pictures that show the blocking behind the flashing to prevent the problem you're experiencing (and allowing the horizontal edges of the plywood to be fully nailed off to take care of the shear load). You pretty much have to pre-bend the flashing to provide a bit of an outward slope so the flashing sheds water more readily. In your situation I'd have considered using heavier aluminum trim coil and bent up some flashing on a brake so there'd be nice straight lines and the pitch would be built in.
In construction when you run into a problem, and you've done some of the work and backed yourself into a corner, you sometimes have to take a step back to go forward. Before you take any steps, forward or backward, ask somebody for directions. All of this stuff is a learning process. You can either find out the problems on your own and on your own dollar, or let some people tell you some war stories. Have fun with it.
R
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So you're talking about something like Thompson's, just not that brand? Will that go on without issue on the edge that already has the stain? Then it sounds like you're saying I can stain over it without ruining it's preservative properties?

Is there any way to pre-bend the flashing without a brake? I tried by hand and couldn't do it. Well, not on a long piece anyway. It's easy on a short piece.

I'm trying and having some success ;)
I did some more testing this afternoon. I wanted to make sure I could reproduce the problem with my hose, which I can. So I took the hose to my test wall that I built before the most recent phase, and no matter what I did I couldn't make it have the same problem. Here are the differences between my real wall and the test wall:
1. the real wall's flashing has a light coat of stain on it 2. the real wall does not have stain up the back side of the cut panel (test has up about 1") 3. the real wall's flashing is, in some places, just barely angled upward at the front because I shoved the lower panels up against it a little too tight when nailing them in 4. the real wall's upper panel face needs stain badly
I don't think the last one is the culprit because the backside doesn't get wet anywhere other than the edge. I also doubt that #1 is the culprit, although it could be that the stained flashing doesn't shed water as well as the unstained flashing. But I'll always need to get in that gap and restain the edge over the years so I'm not sure how I avoid it (not to mention it looks better to 'hide' it with some stain).
That leaves #2 (no stain on backside) and #3 (flashing angle). If I tore it apart I could do #2 fairly well even though that upper panel is in place. I could even get a little under the studs since I'm prying/cutting any nails on the bottom several inches to get the flashing up there. On my test wall the upper panel was from a scrap I stained before installing so it's stained nicely on the back 1" or so. #3 also seems like a contributor. I had hoped it wouldn't be enough to matter, but maybe it is. My test wall doesn't have the flashing angled bent down at all and I'm not having the problem there.
I'd like to save what I've done so far, though if that's not possible I'm ok with it. Frankly I'd be happy to tear it all apart and start over if I could be sure the next iteration would work. It sounds like my first attempt should be some wood preservative on the edge. If that doesn't work, then I'm probably looking at tearing off and starting over with 1) staining and preserving a bit up the backside as much as possible, 2) pre-bending the flashing or at least not unintentionally bending it the wrong way, 3) continue with the 3/8" gap, 4) consider some blocking behind the cut edge.
For that blocking, I presume we're talking about 2x4s toe nailed so that their short edge is behind the cut edge for nailing. Actually, above the cut edge a bit so that I'm not nailing through the flashing, so up 1.5" from the cut edge?
Thanks R and everyone else!
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Let us know how you remedy the situation.
It nice you're able to see behind the siding, if only in one place, there is a problem.
I could believe it the same reason, T1-11 rots prematurely around here. Only nobody knows there is a problem, because they can't see the backside.
In any event, I said from the beginning I'm not a big fan of the z strip for this purpose. I'm sure it could be alright, but rarely are panels stained b/4 they are put up. I have to "LOL" at myself, I tried it to stain the entire panel b/4 putting them up. I found out you never let the sun hit the panel b/4 it goes up, while still wet. I found out the panels take a banana shape, only worse. 8-)
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Indeed. I started on the back wall of the garage figuring I'd work out all the kinks there. What I didn't think about is that it has a bit of a roof overhang and so the wall doesn't get near as much water in a rainstorm. So I didn't catch the problem until the second wall.
I'm sure you're right about most people just not knowing the problem they're creating. The 8' horizontal joints on my house are all 0" gap between flashing and siding, and the siding is buckled out in some places as a result.

Cabot, it's nice to hear that even you have some LOL moments like that. Your work looks fabulous.
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Consider the possibility that with the bigger gap any blowing rain can now hit the flashing and bounce upward into the upper paneling. If this is happening, a bigger gap will likely increase your problem rather than lessen it.
KC
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ben wrote:

Hard to tell from the pictures, due to the wide-angle lens, but that sure looks like a stepped wall to me. I don't see any angle to the siding at all, which an overlap on a flat wall would create. I'd be curious what a long straightedge held against that wall would show. It does look well-sealed. How long does whatever it is sealed with last before it needs refreshing? And what is the climate like there?
-- aem sends...
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