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phatty1978 02-14-2010 12:38 PM

Shed dormer addition help
We have a Cape Cod style house and we will be adding a shed dormer to the back of the house. The dormer back wall will be built on top of the first floor back wall (for load bearing purposes). Our current roof pitch is 12/12, which means the current floor joists are angled at the ends to match the roof pitch. When we take the old roof off and raise the new dormer end wall, we'll obviously need to do something about the end of the joists that are angled.

What's the best method to deal with this? Sister smaller joists that will reach the edge of the first floor top plate? OR
put some blocking in and then cap with a rim joist? OR
something else?

Thanks for the help!

handyguys 02-15-2010 02:32 PM

I subbed out the framing when I did this exact project about 15 years ago. As I recall the framer cut the ends of the floor joists to add a rim joist and then 3/4" ply over top. The floor joists I think only had a minimal notch out of the corner so no additional blocking or sistering was required.

he then built a false mini roof tacked to the outside that matched up on the sides like this

phatty1978 02-15-2010 03:45 PM

Thanks for the reply! That solution sounds reasonable to me and what I was thinking we'd do. We'll review with our architect guy when we review the plans.

Thanks again.

handyguys 02-16-2010 09:00 AM

My guy also built me two "dog house" or gable dormers on the front that were 6' wide each. My shed dormer was 38' wide on a 40' cape. I went from a 12/12 pitch to a 2/12 pitch on the shed dormer. I used a modified bitumen torch down roof on top of the dormer due to the low slope. EDPM would have also been a good choice as are some newer cold applied adhesive roofing materials. Don't shingle a low slope roof.

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