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How to flash new roof butting shiplap?

| Posted in Construction Techniques on November 25, 2002 08:28am

I am adding a new section onto the back of my garage, simple gable roof. The new roof will have the same pitch as the old, but be dropped just below the old roof, tucked under the 6″ eave. Both roofs are 6 in 12 pitch. Asphalt shingles.

The new roof will butt up against #106 style wood siding. It is 6″ tongue and groove, with a cove indentation on its top 1 1/2″, sloping concavely into the tongue. It went on flat, not lapped.

So typical stepped flashing won’t work, right? Can’t get it under the siding. I could cut a kerf into the siding, parallel to the roof slope, but this seems less than ideal. The siding is only 3/4″ thick, without any ply backing it up (60 + years old). Also, everywhere the flashing crosses a coved section of the siding, it will not penetrate deeply enough unless I make a cut most or all of the way through. I could cut that deep, and add backing from the inside of the old garage.

Or I could use water and ice barrier covered by a trim board and hope for the best. Come on you construction geniuses, I know you can work this out for me. Thanks…

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  1. strider7tk | Nov 25, 2002 09:11pm | #1

    Okay, so it is stupid to post another message so soon after my first, but I may have come up with a solution. What if I just cut through the tongue of the siding where it intersects the new roof? That way I can insert step flashing through the siding and bend it up on the inside of the existing garage...

    1. r_ignacki | Nov 26, 2002 02:47am | #2

      just slam the step flashing up to the siding, then counterflash as you would a brick wall, sliding the counter flashing behlistening for the secret.......searching for the sound...

      1. r_ignacki | Nov 26, 2002 02:48am | #3

        ....ind the tongue.listening for the secret.......searching for the sound...

    2. calvin | Nov 26, 2002 03:12am | #4

      I was with you there after your first post, but now i'm confused.  Initially I see the problem with no sheeting, you just can't cut away the siding, and install a new freize (that spelling doesn't look right) board that would be run with the roof and be held up above the new shingles an inch.  You could have over flashed your step flashing with that freize board.  If you cut out the siding where the freize board would go, what's left will flop around.  Can you get inside the old wall to block the existing siding up there if you were to wanna install a freize?   I'm not clear on how you're old and new meet.  Can you post a pic of it?  Here's an add on I was able to step flash to the existing fascia.  The existing fascia then counterflashed the steps.  I don't know if your wall and roof lines would permit you to do this.  However, it might give you some ideas.  Best of luck.__________________________________________

      Remodeling Contractor just outside the Glass City.

      http://www.quittintime.com/

      1. strider7tk | Nov 26, 2002 10:12pm | #5

        Calvin-

        Sorry, I don't have a picture. And part of the problem may be my inexperience. But I will try to describe it better. The existing garage is shaped like your basic doghouse, simple gable roof. The new addition has the same shape, just a bit smaller. It is going to but into the end wall at the back of the existing garage.

        Now, the old part is sided with 3/4" tongue and groove siding, which has a concave cove near the top, leading into the tongue. The siding is not lapped. Any board I nail across the siding parallel to the roof pitch will not contact the siding at each cove. Seems to me the only way to have continuous contact with the siding is to cut a short slit through the tongue of each piece of siding above the step flashing, so it can insert into and through the siding. I don't see how anything parallel to the roof overcomes the gaps at each cove; instead, it has to go parallel to the siding.

        If you are still having trouble visualizing this, try making a series of question marks on a sheet of paper, one stacked right above the other (leave out the dots). That's the shape of the siding in an exaggerated form. Thanks for thinking about it!

        1. calvin | Nov 27, 2002 05:06am | #6

          I think I know what you are talking about.  I once saw a roof flashed into (on to) what is called garage or something else siding around here.  It has a dished out part above a flat plane in the siding.  They step flashed the shingle over that siding, beating the crap outta the step flashing to conform to the siding profile and then they nailed the heck out of it.  Bass ackwards it was, probably held out most of the water.

          Now, I still cant see how you are going to slit that siding so you can put the upper leg of the step flashing into it.  If you went that route, I would think you'd have to slit a continuous groove through the siding and all the way up the wall (parallel to the roof).  What I was trying to show you in the previous attachment was flashing up under the fascia of the old existing bldg.  The fascia would then counter flash the step flashing.  Your new roof would be below the old roof and you would frame it low enough to have about an inch between the shingle and bottom of the fascia.  Otherwise I would block behind that siding, cut out a strip of siding the width of a complimentary square edged frieze board up each rake and step flash the new roof under that frieze board.  I don't like to just flash to siding as that's alot of wide open end grain just dying to soak up water.

          This is hard to explain in english and I am sorry.  What ever you decide to do, best of luck.__________________________________________

          Remodeling Contractor just outside the Glass City.

          http://www.quittintime.com/

        2. Piffin | Nov 27, 2002 05:59am | #7

          http://www.woodsiding.com/pattern.htm

          from this page , I believe this is the novelty siding you are describing. The world is full of garages built with this as siding and sheathing in the thirties through the sixties, as I understand it.

          Just how far below the other roof is this new added one? and what is the overhang of the previous soffit? I was picturing this much like the photo in an earlier post and the best solution is to wiggle in some flashing under the overhanging soffit and not worry about back at the wall if it is similar.

          If you really need to flash at the wall, here are two options:

          Use lead to make the step flashing. It easily conforms to shapes and you can caulk behind it with the top of each step vertical cut right under the lap of the siding. If the siding is true shiplap style, you can pry it up enough to get behind it a little. If T&G, don't try that.

          Lay a scrap of furring or sheathing on the roof surface for a guide and run a router down the siding with a 3/4" dado bit chucked in and set for a depth a little more than the void created by the bevel gouged out in the siding. Make a dado parallel to the roof. Now make a piece of 3/4"x1" fir that will fit into that dado. Run your flashing to the bottom of that dado with caulk behind it and then glue and screw the dado fill piece into the dado to aact as a minimalist counterflashing that can still help hold the wall sheathing together.

          or

          just lay the flashing ind and install vinyl siding over the whole shebang..

          Excellence is its own reward!

          "The first rule is to keep an untroubled spirit.

          The second is to look things in the face and know them for what they are."

          --Marcus Aurelius

          1. strider7tk | Nov 27, 2002 06:37pm | #8

            Piffin and Calvin-

            Thank you , guys, for the thoughtful comments. It took a while for me to visualize what you were suggesting regarding using the existing fascia; now I think I've got it. That does seem to be the simplest way to go. I can frame the new roof right under the old to make it work. I guess I was making it more complex than it needs to be!

            The other ideas are creative, and appreciated. Hopefully I will not need to go there.

            If I step flash to the fascia, in the manner Calvin did in his phot (nice job, by the way), I assume I have to start theshingling directly below the fascia, and not where the new roof butts the old wall. The 6" of new roof under the old roof can be protected with membrane, in addition to the protection the existing roof overhang will give. It will be mostly closed up anyway. Should I leave it open at the gable ends (shingling up a ways), seal it off, or block it off but with some venting?

            Thanks.

          2. Piffin | Nov 27, 2002 07:50pm | #9

            Venting couldn't hurt but definitely don't leave it completely open or it will be a haven for wasps to nest. You could run the first shingle or two all the way back so it looks natural from the ground..

            Excellence is its own reward!

            "The first rule is to keep an untroubled spirit.

            The second is to look things in the face and know them for what they are."

            --Marcus Aurelius

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