How flash valley between two gambrels?
Got to thinking about this, since I am theoretically supposed to start shingling (on Monday) the roofs where two gambrel roofs meet at 90 degrees. Valley flashing in a valley between two regular roofs of one slope each is straight forward, but what do you do where the slopes on the roofs change? Can’t bend the flashing once you put the “V” in it! Butting the pieces seems like it’ll leave a part unprotected right at the break.
Guy that’s running the job wants, and has already purchased, the metal flashing. With Water and Ice, I could maybe have done something to cover the problem spot, but metal is pretty unforgiving.
BI never showed up on Friday, so I don’t even know if what we did with the felt will meet with his approval. I don’t know why we didn’t just use W&I like I suggested (and the BI wanted, as I learned belatedly–after putting on 30# felt) on the low-sloped top.
I may not be long for this job–it’s wearing me out!
I was trying to calculate the slopes and realized the lower part is 20/12, because it rises 40 inches over 24, so divide by 2 (so denominator becomes 12) and you get it easily. “Boss” is still telling peopl it is 10/12. Top, to my measurements is 20″ rise over about a 60″ run, so 1/3 becomes 4/12. I think that is okay, but “boss” used the carpenter’s square and read 3-1/2 over 12.
I think you need roll roofing under 3, so I still say we’re okay, but…
The other problem is that the lady who runs the building wants storage up in the trusses, so I said that limits the depth of insulation–except at the edges, we can just insulate the bottom chord of the truss (3-1/2″ or R-11). “Boss” says we can cram more in on top and so what if the planks thrown up there for storage compress it? I guess if it were my job, I would put 2″ of Styrofoam at least, under the planks. But so far, I haven’t been listened to and doubt anyone’s gonna start listening now!
Replies
I've done this a lot on small stuff; don't see why it wouldn't work on your flashing.
Hammer and dolly, or use a shrinker / stretcher to shape the curve. This was an early experiment starting with a 9" long angle bent from aluminum, prior to filing and smoothing -
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Forrest
Edited 8/23/2008 2:38 pm ET by McDesign
Sounds like your week was less pleasant than it coulda been, LOL....
I assume the upper roof of this gambrel rolls right into the lower roof (if there were an eaves or a weather lip, you wouldn't have a problem). As you pointed out, this complicates the valley flashing. My solution is to cut the flashing on one side of the valley crease to allow it to be folded over the transition ridge on the other. That cut leaves a pie-wedge of unprotected roof once the flashing is folded over the break. To cover this, a separate, complementary piece must be made which is darted or cut on the opposite side of the crease. (Typically, that piece will only need to be 2-4' long.) This is laid notch-into-notch against the the full-length piece of flashing, with the upper flap on the cut side going under the main flashing, and the lower flap laying over it.
The weak point, naturally, is at the apex of the two notches, where they meet. In the past I've put pitch under and over that spot and gotten reasonable service out of it, but I would think that the best way to waterproof this is to solder it together before installing it. I'm not equipped to do that, unfortunately.
Maybe Grant could chime in on this one.
Dinosaur
How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....
Thanks for the reply. Yes, the top roofs just break and follow a steeper slope without any trim or whatnot. (This will also entail heating the shingles (I vote for just putting them in the sun, bending them, nailing them and tarring the tabs, but "boss" says he has a heat gun--sems like a mighty good way to damage shingles (and hands!).)
Took me a couple readings to folow what you said, but I got you. Better than my idea to split the upper flashing longitudinally from the break point down and overlap that onto the lower piece, but it would have to "flare" out and so there would be a little spot without flashing. With your way, there wil still be a teeny area unflashed, but like you say, that can be covered with another piece, and i have some aluminum tape I can also use.
Just got off my cell phone with the boss--my work is cut out for mr Monday because I am supposed to pick up four ten foot sheets of DW for the ceiling and get them in there--wight now we have an unsheathed area between two studs and I can get the DW in there that way, otherwise we have to wrestle it through the old building and throuhg a door way that hasn't been cut yet (that's the second thing I get to do on Monday--shore up the wall and trusses where they land on the old wall between old and new and put in a header and then shingle!
I may have one or two guys helping me, but maybe only one. Boss says the BI is okay with what we've done as far as shingle underlayment with the doubled 30# felt. I have to put on flashing and drip edge before I start shingling--this all could be lots of fun! Better rest up something fierce this weekend! Where's my opium pipe! (Just KIDDING!)
Took me a couple readings to folow what you said, but I got you.
Yeah, I wanted to make a drawing for you, but the only 'graphics' program I've got is ACAD. And I am so pathetically bad at doing 3D stuff on ACAD that I finally made a quick 3D paper model of the roofs and flashing instead, LOL. I was gonna photograph that and post it but what Grant suggested looks to be a bit less fiddly.
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
bump
Lay the steep valley so it's about 5"-6" above the pitch change. Cut it in the center and neatly fold it on the pitch change.
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If the metal your using is solderable (hopefully it is), solder a piece in to fill the void in the center.
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Then make a neat cut and hem on the bottom of the 1st lower pitch valley piece. Let it extend a couple of inches past the lower valley and fold it cleanly over to match the lower slope. I would also rivet in a matching piece to fill the center void for cosmetics.
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If the metal is not solderable, rivet the piece in after setting it in something like Geocel 2300 caulk. Do not use roofing cement (asphaltic base) on any ferrous metal. It is corrosive to it.
Re: roof slope. To the best of my knowledge, most shingle manufactures spec felt under dimensionals down to 3/12 and 3 tabs to 4/12. With I&WS you are allowed to go down to 2/12 with dimensionals and 3/12 with 3 tabs.
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Thanks for the nicely illustrated reply.
I found out lots of stuff since I posted this!
The boss called me on my cell while I was posting the original question and added to my list of things to do! But then, another guy called and said he'd help and also knew a guy that may be able to help with the drywall.
I was thinking the ceiling had to be 5/8"--still think that over the bottoms of trusses at 24" o.c., it would be best, but code only requires 5/8" in garages, so I guess I won't fight the boss and use 1/2" like he wanted. I will rent a lift (since it's only $25 a day) and then I can hang the four sheets myself and not worry about helpers and people killing me by not knowing what thye're doing while they help me with deadmen.
I also found out that Marc will loan me his nail gun and nails only cost $25 a box, so if need be, I'll use my own money for them. It's crazy to fool around hand nailing on a gambrel roof. (The other "helper" who wil be doing electrical and helping header over a doorway, told the boss that it'd be easy for me to just hand nail--it's only 4 square! Nice to have other people determine what is easy for me to do. I say that he is welcome to hop right up there and do it himself if it's so easy!