Replies

1. 
   DanH | Feb 24, 2016 02:10pm | #1

   Just speaking as an observer here, who once shingled a small garage, but that's about it, my impression is that "modern practice" prefers (for both quality and laziness) overlapped valleys for shallow slopes, but that when you get up to 12/12 it gets harder to bend the shingles to fit.  So what works for standard weight shingles might not work for archies, etc.

2. 
   Mongo | Feb 24, 2016 02:53pm | #2

   Varying ways

   Yup, many different ways, you sometimes have to cater to the manufacturer's instructions, sometimes to local code. Check through those and see if you have restrictions of guidelines.

   I'd always recommend use a membrane like Ice and Water on the valley sheathing, even if covering it with a metal valley. I do prefer W valley if using metal.

   Open versus closed valley? Woven versus cut? In a historical application one may be more apropriate. Heavy laminated can sometime look clunky when woven.

   So...

   See what the shingle manufacturer recommends..or requires, if anything.

   See what your local jusidiction requires, if anything.

   See what will look appropriate on your house, or in your neighborhood if that's a consideration.

   Combine all the above and specify what detail you want.

   Make sure the installer can do the valley type you specify correctly. Not all can. Not all care if they can't. It might help to print out a detail sheet, have it dated and initialled, and have it become part of the contract.

3. 
   finefinish | Feb 26, 2016 10:09am | #3

   Hi Stalker (just kdding), 

         I prefer an open metal flashing for a valley on a steep roof like yours.  We generally use copper, zinc coated copper, or galvalume.  We never use aluminum, mostly because our work is in coastal New England and it won't hold up, and aluminum doesn't jive with the period architecture we are typically matching.  

          Our basic procedure is this :  

         We install Ice and WaterShield in the valley first, then cover the rest of the roof on either side of the valley with Ice and WaterShield lapping onto the valley membrane.  The eaves' drip edge goes on at the valley location and the valley metal has a tab at the bottom that folds over and hooks the drip edge.  The long sides of the valleys are also folded over to receive the flat metal clips that secure it to the roof deck (same metal and fastener material).  There should be no holes in the valley for a couple of reasons.  One is that is a potential leak spot, two is you don't want to restrict the movement of such a large piece of metal.  The clips allow for the valley panels to slide and move a bit without distorting.  The shape of the valley is important too.  We form a "W" - valley.  This has approx  a 1.25" tall ridge running down the center that keeps water running down the valley and not across it where it could get up under the opposite side.  The extra couple of bends that form the "W" also hide or reduce the movement of the panel, like a shock absorber.  We typically hold the shingles back from the center of the valley 6 or 7 inches, so a foot or foot and a half of metal shows.  This allows snow to slide off quickly and keeps debris like leaves and sticks, etc. moving too.   On most new roofs we cut the shingles parallel to the center of the valley.  Sometimes we see valley cuts that taper, getting wider at the bottom and almost closed at the top.  

        I think the open metal valley is the best looking, and performing installation, at least for my location.  I don't think a cut valley looks very nice and a woven corner is out with thick architectural shingles.  In your case, with a Victorian, an open valley is probably what you had originally, because it was what was used with slate tile roofs.  

       I am really lucky to have a top notch roofer/metalsmith on call for all of my roofing needs.  When I say "we", I really mean "he, my roofer".  I am the GC and carpenter and we always go over what system we are going to use with the roofer before he begins.    

         One last note to consider is cost and value.  The valley metal should last at least (maybe twice as long) as the shingles you are putting on.  Copper and other decent materials are pricey up front but to me represent good value in that they last a long time.  An alternative is a painted and clear-coated metal that may cost less and have similar lifespan.  Good luck with the roof project.   

1. 
   Geoffrey | Feb 28, 2016 04:15am | #4

   Fine

    fine,

   excellent method you detailed,

   One thing I would add is, after placing the valley flashing, I snap a line on the valley  flashing indicating where the shingles will

   be cut on each side of the "w" center, also I  do not nail the valley shingles any closer to the valley  than 12-16" away  from that

   line.Then, after the shingles are installed I go back and apply a "line" of roof cement 1" back from the chaulk line and

   approx. 2" wide, along the flashing, from top to bottom on both sides of the "w" center. This seals the shingles to the valley

   flashing and helps keep water from being driven under the shingles, or harmed by wind uplift, and not having any nails closer

   than a foot or so from the flashing allows a little flex in the shingle/flashing assembly....... and no accidental nails

   through the valley flashing.

   just my 2cents worth.

   Geoff