I build a two story house and I at the point of doing the plumbing.
I would like to put my 3" wast pipe in the out side wall to go down to the basement the only option I have . My question is that I have to cut through the top and bottom plates of a 2x6 wall . Dose code allow me to do this and will I weaken the structure.

Hi Bobby... 3" waste stack is perfectly OK in outside wall. You will not damage the structural integrity of the building by cutting into the 2x6s.

I have installed many stacks in outside walls...never ever an issue. Just keep the hole to 1/4 to 1/2" larger then outside diameter of 3" pipe and you should be good to go! Hope that helps you!

Keep us posted as you go along... glad to help as you progress!

Talk later, Mark

I would like to put my 3" wast pipe in the out side wall
Are you planing on running the vent through the soffet and out the roof? Because if you're planing on terminating it under the soffet there are a few resistrictions. You may not terminate the vent under a door, window or any other ventilation opening, nor shall it terminate within 10 feet horzontally of such a opening unless it's 2 feet above such opening. Just thoughyt I'd give you a "heads up". Good luck, Tom