Venting Plumbing AFTER drywall is up

Question

First, some set up: My friends and I have been building a sort of Mancave over the last year. It's about 300 square feet, with a height of about 14 feet -- half of the place has a loft (making something like 2 floors) while the other half has tall ceilings.

We initially did not have plans to put in a bathroom -- so, we put drywall up everywhere. THEN, we decided it would be nice to have a bathroom. We ran all of the water lines from city water up into the crawlspace (passing inspection), but now are preparing to tackle the bathroom.

My question: With the drywall up, and roof shingled -- and the whole place basically ready for use.. we are putting a bathroom in. Under the loft, we have built a 2x6 dividing wall for all of the plumbing to sit inside (just the studs right now). HOWEVER -- we did not realize, being newbies, that you need a plumbing vent stack. The question is, can we possibly vent our plumbing for an entire bathroom WITHOUT penetrating the roof?

There is a somewhat tall crawlspace under the building. Could the drain just be low in the crawlspace, and have a vent that angles out through the rim joist and run the vent outside? I have read that it is possible to vent through an exterior wall -- but as this 2x6 wall is in the middle of the house, reaching an outside wall might be difficult.

What is my best option? I really appreciate any help!!

P.S. I will be making sure any plans pass inspection before doing the plumbing -- Any help I get will go toward my plans.

Answer 1

To vent plumbing you must either find a way to tie into an existing stack vent, go to the outside via wall (this is code depending on area and must be higher than all fixtures - what you are describing is not), or go through roof.

If the roof is available this is probably your easiest option. You drill a hole and throw a roofing vent with gasket over the hole, caulk gasket, plug pipe in bottom of vent through hole and you are done. This is a very easy, forgiving process. With materials in hand you can do this in 30 mins. So just do it right.

Answer 2

Depending on your local codes, one might use a studer vent at the end of a short vent pipe (higher than any sink bowls/toilet resevoirs in the basement). Such a vent isn't allowed to be within a closed off space (ie. within a wall) ...as there's be no make-up air.