I live in Wisconsin

I have added a porch where my deck was previously. My home has a 4-12 pitch truss roof and I purchased 4-12 scissor trusses for the porch. the porch will tie in perpendicular to the house - a gable I believe it is called. I have pulled info off the web regarding the tie in as to lumber - 2x6 ridge board will be about 95" long with 3 rafters on each side tieing into valley boards nailed to roof.

That said - my question - They have not covered how to tie into the existing roof's asphalt shingles. Do I strip off all of the shingles in the tie in area? I was hoping to put down ice dam membrane right over the existing shingles and roof cement the upper seam. Would you suggest valley flashing.

The house roof is about 10 years old and I will probably replace in a couple of years. I just dont have it in this year's budget after the outlay for the window porch.

thanks for your assistance,
bubba the viking fanatic

 

Take a bright colored ink pen or even tack a 1x4 to your roof line where the new roof line will meet the old one. You will have to take off the existing shingles in this area.
Take them back an additional 6 inches cutting on the diagional and yes, then flash this area. Use 12" flashing sliding 5 inches under the existing shingles. Even with the flashing, I would probably used a closed valley when roofing the new addition.