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joshnoiseux 10-31-2012 08:04 PM

Vent stack ruining dormer plans!
Hello everyone

I am in the process of adding a large dormer to my roof as part of a major attic renovation. My house is 36x41' with a hip roof. Rafters are 2x4s on 16" centers.

My problem is that the main drain waste stack comes up right in front of where the dormer window will be, only a foot or two away from the corner. It is a cast iron pipe. At the moment I can conceive of two options for how to deal with this.

1. Extend the pipe higher than the dormer window, in order to meet code. Relatively easy to do I guess but then there is a big pipe in front of the window.

2. Put a 45 degree elbow on the pipe and have it go along the underside of the roof 10' away from the dormer then come out there. The problem with this is that it seems to be against code to have the vent stack bent in any way.

I will post pictures of this shortly.

Thanks for any suggestions


Anti-wingnut 10-31-2012 08:17 PM

Vents are bent all the time

joshnoiseux 10-31-2012 08:21 PM

Thanks for your reply. Can you give me some more info on that? Is there a limit to the angle it can be bent at etc?

Anti-wingnut 10-31-2012 08:29 PM

No limit, just no sags. No horizontal runs inclined at less than 1/4" per foot

joshnoiseux 11-01-2012 10:18 AM

1 Attachment(s)
As you can see I don't have a lot of space to work with here. If it were to go under the rafters it would be more like a 50-60 degree angle I think.

Any ideas?

ddawg16 11-01-2012 10:48 AM

What is your roof pitch?

They make the ABS angles in 22, 45 and 67 deg sizes....

Cut the cast iron off using a sawzall (I lot easier than it sounds...yes, easier)

Use a rubber coupling to couple a street elbo of the right angle in....angle does not have to be perfect...the ABS has enough give as well as the rubber coupling.

And as the guys above it up the roof to a new location....

Anti-wingnut 11-01-2012 11:04 AM


Originally Posted by ddawg16 (Post 1042404)
What is your roof pitch?

They make the ABS angles in 22, 45 and 67 deg sizes........

And two 90*ells put face to face can make any angle in the world

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