Please help me vent this bathroom

[JeffG2583]

Hi everyone, so I'm working on plumbing my master bath and need some advice on venting. My plan was to vent the double sink by going up the wall behind it, but can't do that because there is an I-joist that sits right on top of the wall. There's just no way to get a pipe up the wall without having to drill the I-joist and I haven't found anything that says I can do that. I could go across the wall into a wall past the I-joist but then I feel like I'm drilling a lot of holes in that wall and it transitions from 2x6 wall to 2x4 wall as well. I'd have to drill a lot of holes to make this happen. So I'm wondering what my other options are. I will have a 3 inch main line running right under the double sink that will go out to the septic tank. If you will help me solve this issue I will make a donation to the site. Thank you all for your time.

 

[MicEd69]

So, there is an I-joist running along the 2x6 wall. I assume that means there is a second floor above this bathroom. And you absolutely do NOT want to drill a hole in the flange of an I-joist. Once you get 6" above the flood level of the fixtures being vented, you can run vent lines horizontal, sloping them 1/8" per foot just like drain lines back towards the drains. Drilling holes in studs isn't a huge problem and is done a lot.
I dislike Air Admittance Valves, AAVs, but you could use them under the sinks or combine the vents in the wall, which will involve drilling the studs, and use one AAV in the wall for both sinks. If you put an AAV in the wall, it needs to be accessible. Use something like this:


The access to the AAV could be from either side of the wall.

 

[Twowaxhack]

I’d drill the holes once above flood level and go horizontal with a common vent for the two lavs.

If I used an AAV I would just install it in the cabinet.