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moparman56 10-29-2009 12:34 PM

Can I shingle a dormer without re-shingling the main roof?
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I am finishing the construction of a new porch that wraps around the front of my house. It's getting late in the season (Pennsylvania) and I have been trying to wrap this up between rain / snow days.

I was planning on building a dormer on the front porch roof but I already had the new sheathing and underlayment down and with over 2" of rain on the way I ended up shingling the entire roof to protect it.

My mistake was that I didn't take the time to consider how I was going to run the valley off of the dormer. My initial thoughts were that I was just adding an unnecessary area of shingles under the dormer and that they would just be hidden.

Now I realize that there is no way for me to tie the main roof and the dormer roof together nicely at the valley.

I can't see the process of cutting the new shingles and slipping any flashing under them coming out well. There is also a lot of work and money there to rip them up and lay down new ones.

I have attached a photo of the roof in it's current condition. What are your thoughts?


ArmchairDIY 10-29-2009 01:27 PM

As I see it you really only have two options.
  • A cut Valley
  • An open valley with "W" flashing

And unfortunately both require removing the shingles to some extent.
It does not appear to be a large area. I think you will just have to put your mind to it and race the weather and get it done.
Sorry, the right way is seldom the quick and easy way.

VA metalman 10-29-2009 06:23 PM

Hey, moparman,
I see your hindsight is 20/20. Live and learn.

BamBamm5144 10-29-2009 06:45 PM

Are you still in the process of the main roof because it looks like it is missing ridge cap. Also, you need more support for the dormer than what you have. Put another 2x6 or whatever you have in for support. The right way to roof it would be to tear out the shingles a shingle width for when you roof up the valley. I recommend using a Metal W valley. The only way for to get done right, is to tear out some of the work already done, roll some ice and water shield down the valley, put the metal valley in and roof it.

meboatermike 10-29-2009 08:31 PM

metal W flashing
I hope you can get it in your area quicker then up here in Maine -- I called all over the state when doing a roofing project earlier here this fall and found out no one stocked it -- it was order only. Good luck and good luck wrestling with the ice and water shield also :whistling2: I destroyed more then one piece but did avoid getting it totally wrapped around my body :laughing:

moparman56 10-30-2009 05:13 PM

I just took this photo the morning after I finished laying down the roof (Wednesday). I haven't capped the ridges yet. I realized the valley dilema the night before while I was working on it but had to get it covered because it was raining.

Right now I am planning on chalking a line and setting the blade depth on an old circular saw blade to 2 singles. I'll make the cuts and use a bar to lift the roof enough to get a W valley under the existing roof.

The most popular opinion seems to be that I can make it look good and also keep the integrity of the shingles with a W valley on there.

I know I'll need more framing for the dormer but even though I used treated lumber I still like to keep the exposure to a minimum until I'm ready to close it up.

My local hardware store doesn't keep the "W" in stock. They told me today that I should be able to have it for Wednesday. I hit the HD this afternoon and they have a nice picture of it on the flashing rack but the "I don't know - I just started here" guy said he has never seen it before.

I'm hoping that I can get the shingles on top of the W valley to lay down nice and tight.

jogr 10-30-2009 05:25 PM

Sounds like a bad idea to me. Take off whole shingles at the valley to expose the deck wide enough for I&W and w flashing. Put on your dormer sheeting, lay down I& W all the way to the eave, install w flashing. Install new shingles on dormer and removed area. It will be easier, less messy, look nicer and be less likey to leak.

Treated lumber to frame the dormer?? Has it started twisting into a pretzel yet? Did you use hot dipped galvanized framing nails? Have you got hot dipped nails for putting down the roof sheeting?

moparman56 10-30-2009 08:20 PM

Actually, the entire porch was framed out with treated lumber. Unorthodox I know, but it was such a wet summer I didn't know how long it would be exposed before I could get it covered. That and the cost of PT being only a few cents more than standard pine right now I figured it was a good investment.

It was secured well and it hasn't twisted and warped at all. Usually the few bad ones that are going to act up bend around and touch themselves within a day of sitting in the pile.

I had ceramic coated screws left from the deck flooring so they worked perfectly to attach the sheathing to the rafters.

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