How I finally solved attic vent routing — steps that actually worked

I did this exact project last summer when I was trying to floor my attic for storage. The builder had a 2-inch vent stack cutting right across the center at a 45-degree angle. I followed the logic of pushing it back toward the eaves using a couple of 45s. I actually found that using a Fernco coupling on the bottom side made it way easier to line everythign up when I was working solo in a cramped, hot attic.

One thing I’ll add is to watch out for the roof pitch when you’re cutting your new hole. I used an Oatey Master Flash since my shingles are older and I didn't want to risk cracking them by prying them up too much. I ended up moving the exit point about four feet higher up the roof. It cleared up enough space to fit three extra Husky bins right against the knee wall.

The only issue I ran into was the condensation. I didn't wrap the new run at first, and because it was closer to the roof deck, I noticed some moisture on the outside of the pipe during a hard frost. I ended up throwing some basic foam pipe insulation on that new stretch just to be safe. It’s alot of work for a few square feet, but not hitting my shoulder on that PVC every time I grab the ladder was a win.

If you are prying up old shingles to install that new vent location, skip the standard plastic bases that crack after three seasons. I always swap them out for a Lifetime Tool Ultimate Pipe Flashing. It uses a silicone compression collar that won't rot out like the cheap rubber boots you find at the big box stores. Since you're alredy moving the stack to clear space, it’s the best way to ensure you never have to climb back up there to fix a leak around the pipe.

Back in the day, we’d just use a torch and lead to sweep these around, but those days are gone. If you're moving that stack, watch out for the pitch—plenty of guys think they're being smart by going horizontal to save space, but you need that quarter-inch per foot slope back toward the drain. If it sags, you're looking at a sewer gas blockage once a little water builds up. Also, skip the Ferncos if you can help it; a proper solvent weld is the only way to sleep easy when the house starts shifting in the winter. Seen too many rubber couplings slip when the wood dries out and pulls on a new build.