I am an owner-builder of a timber frame house built on a slab and having a loft bedroom and dormer windows lining the main roof (16-12 pitch) with the master bath in one of the sheds lining the full length of main portion with the loft. I am doing the plumbing and pulled the permit personally. I have researched my problem of how to run the vents in about 10 plumbing books but they all deal with conventionally stick-framed houses with attics and basements and don't cover my problem. I have one drain directly underneath a timber "outshot tie beam" which is in turn directly under a timber rafter. I can work the vent for it around a corner and into the adjacent wall where I have two other drains needing vents. If I go straight up through the cathedral ceiling I will exit the roof about 1 foot in front of the series of dormer windows which are about 12 feet apart in a line on each side of the building. Thus, I would have to run the vent pipes up to a point 3 feet higher than the windows which would really be ugly. On the other hand, if I run the vent pipes around the next corner to the next adjacent wall and then out near the edge of the shed roof, I will still be within 10 feet of other windows and doors and will have to run the vent pipes horizontally through the interior walls about 20 feet or so to get near the shed roof edge. What a bummer this is turning out to be. I don't know what to do. To make matters worse, the house will occasionally be subjected to heavy snows (12-15 inches at a time) and the roof will be a standing seam metal roof and another poster to this site noted that the sliding snow can break off vent pipes. I can post pictures if necessary. BTW, I understand that AAVs are not permitted in New Mexico which would otherwise solve all my problems. Any suggestions you can make would be greatly appreciated.

Yep, fully understand your dilemma. Have been in the same situation few times before... It is mostly glitch in house design. Whoever designed the house forgot to take in consideration venting situation.

I would contact your Building Department and present them with your issue exactly as you posted here. Than I would apply for Code Variance for the AAV vents. Get some technical info from AAV manufacturer about functionality of AAV vents and enclose it with Code Variance request. AAVs are used in 1/2 of the country so it is not that they don't work... See how will Building Department respond...

If you know your Inspector and/or have good relations with him, he may allow you to use AAV vents w/o filing for Code variance. Maybe, you can try to talk to him first...

Otherwise, you will probably have to build fake beams, rafters and/or build chases to hide the vent runs...

Let us know how you solved the problem... I am very interested to know the outcome of this situation... Good Luck... Milo

I had that problem in my area some years ago. I took the vents up in the walls and, like Milo sez, we built chases that resembled the rafters and beams in the cathedral ceiling to conceal the pipes and ran them out the roof that way. Good luck, Tom

If you end up going through the roof with your vent, transition to cast iron before it goes through the roof if you are concerned with snow breaking off the pvc riser. Will there not be any snow cleats on the roof?