Replies

1. 
   Piffin | Oct 05, 2006 06:36pm | #1

   you need to get the old shingles off to the wood for a good four feet back from the vally. Do the I&W, then reshingle.

   Wheather you add a shim layer back in is according to how good do you want it to look. You can layer up a few of 30# instead of thje old shingles for this shiming. This is onme of the problems that can come up when overlaying a roof in the last re-roof. Inconvenient isn't it?

   As a roofer, I genrally prefer to strip the exiosting roof all the way back. That is not "green' practce if it is a fairly new re-roof, but most of my customers would always complain they could see the slight diff in colouration of the replacenment shingles from 3 to 6 feet back. And a whoole new shingled side is far less likel;y to leak, so I'd push for the total re-do.

   Some guys willl try to work in the new addition without removing existing, just cutting and weaving in. That ALWAYS results in a leaking valley.

    

    

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2. 
   Hazlett | Oct 07, 2006 02:02pm | #2

    Here is what you do----------

   Assuming the 2 layer roof is in pretty good shape.

   Take a ESTWING roofers bar( or an oldfashioned "ripping Chisel")----not an ordinary carpenters flat bar------------and starting at the top of the valley remove shingle by shingle down the valley about 2 feet of shingle on the 2 layer side of the valley.

   ONLY remove the top  layer

   Do this when the temp. of the shingles is about 60*--------- this will be pretty easy---if a bit tedious working shingle by shingle,nail by nail. Won't take longer than a half hour for one side of the valley. 3 tab shingles in good shape are VERY easy to do this with.

   Instead of ice gaurd-----get a roll of self adhering modified bitumen roofing-------Certainteed Flintlastic,Mule Hide, or polyglass Elastoflex.

   On the new deck the modified Bit. will install on bare wood very similar to icegaurd. On the old roof the modified will be installing OVER the bottom layer of shingles(original roof). Make absolutely sure everything is clean and well swept with no protruding nails.

   Re-shingle the valley using a closed cut system( california cut system)

    work efficiently and thoroughly-----the secret is not to damage adjacent shingles.

   Now----with all that said-------DO NOT do this if you have the slightest question about the condition of the existing roof or your ability to break the seals on the existing shingles with out damaging them.Quite possibly the foot traffic you subject the existing roof to while framing in the new addition is going to damage the old roof anyhow----resulting in a leak adjaecent to and erroneously blamed on the valley.

   good luck,Stephen

1. 
   McDesign | Oct 07, 2006 11:18pm | #4

   Nice post -

   Succinct

   Forrest

3. 
   theslateman | Oct 07, 2006 10:31pm | #3

   Have you thought about using metal for the valley and not using the cut method?

   You could strip back the old roof down to the deck,install the metal,bond onto the metal with ice shield just short of your exposure line,shim up for the first layer,then your top course.

   Of course it would be much better to strip all the old roofing,but if it's not in the  budget.......