Dormer to main roof cap shingle detail. Correct or did I miss anything?

Hello, everyone! Hope Thanksgiving went well! As a slow DIY roofer, I am still tackling the same roof plane. Finally finished both valley in a “dormer” style layout and transitioned the ridge cap onto main roof. I again followed Mike Guertin’s advice on using Grace IWS under the transition cap shingle, then cap shingle cut towards the middle so it can “hug” the dormer while going onto main roof. Then another Grace IWS to cover that cutout. And to make it 100%, nailed a piece of cap shingle to overlap all of that very well before main roof shingles go above it.

Mind you, it is cool and overcast here, so shingles will not adhere or settle probably for another week when we expect 70 degrees with sunshine again. Here is the detail:

Of course, as much Grace as I put there, should the cap shingle crack over time, the leak will be unlikely. Besides what I described above, both valleys are double lined with Grace so nothing should come to contact with deck. Of course, despite my best efforts (using hair dryer to warm cap shingle so it bends better, you can still see below some loss of rocks where the stress bend is). Should I let it be or maybe put a dab of Geocel 2300 on there just to make it last longer before it cracks?

I hope I did this right. Any feedback appreciated before I proceed further. Be kind on an amateur!

View from the top (before I finished capping the vent):

That looks great, much cleaner than many “peofessional” jobs I see.


Haha, thank you, MPA! That’s why I has taken me over 30 days just to complete an estimated 12 squares! Of course, weekends only, since I didn’t take time from work. But I stand behind my statement that I would never make any money as a roofer, I will never meet my stimated time goals and probably get fired. Haha. Do you think leave the transition shingle as is until (and if) it cracks or put a nice dab of color matched Geocel to strengthen the bend? Hasn’t cracked yet but you can see up close where maybe 5 granules fell out from a couple of places. The fiberglass layer remains intact.

With grace underneath you have nothing to worry about.

You have a bright future in roofing if the whole Pharmacology thing doesn’t work out.


I would say it looks perfect.

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I like how he nailed perfectly only on the lower half portion of the sure nail strip…

I wonder where he learned that from…

I thought at first this Sure Nail strip to be a bullet proof way to ensure correct nail placement. Boy, was I mistaken! This enlightenment happened when I came across where 2 shingles from same bundle had not only different widths of the strip but also variable placement in relation to butt edge. Some so high that lower edge of strip is above the laminated connection! Then the instructions said to nail 6 1/8 inch from butt edge no matter whether it goes into the strip or granules. Even if I keep nailing in lower portion, my quality spot checks frequently reveal that I am often over 6 1/8 inches from the edge. So I try to nail it around the lower half, so long as get most nails through both laminated layers. My Hitachi gun skills are fair at best, but I seem to get 80 percent of nails close enough to be within OC specs. Here is a photo of old shingle nailing pattern on the same roof and these lasted 20 years. I just got tired of renailing after each wing gust. Lol. I am hopeful these will do at least that with the effort I put into it. Fingers crossed! But I have found SO MUCH help on this forum from wonderful roofers like you all that I cannot be thankful enough! Many answers have opened my understanding and put me on the right path to a successful roofing project. Time will tell, but I am praying for zero leaks.

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