View Full Version : 4 inch vent pipe in a 2x6 stud wall?

07-31-2010, 03:11 PM
Hi all, I just built a 2x6 stud wall for my new bathroom. I would like to put in a 4 inch vent pipe but I'm wondering if 4 inches is too wide. Obviously there are code issues with boring studs, but what about top and bottom plates? This is a load bearing, double top plate wall. A 2x6 is only 5.5 inches wide and the OD for "4" inch DWV pipe is 4.5 inches, leaving only a half inch on each side of the plates. That seems too big to me. I suppose I can get by with 3 inch. I would like to do to the toilet drain with 4 inch and would like to have the vent be the same size. Is it OK to have toilet drain by 4 inch and the vent be 3 inch?

07-31-2010, 03:19 PM
Depending on the load of your system, you could vent a toilet with a 2in line, unless you have an extreme load on your whole system 3in should be fine.

08-01-2010, 08:49 AM
Plates only support things where they cross. We drill 4" pipes through 6" walls all the time, otherwise there would be no way for us to install our piping.

Wally Hays
08-01-2010, 09:08 AM
Double up the studs on either side of the pipe and plate it when you are done.

08-01-2010, 02:23 PM
NEVER have had to reinforce the wall after installing a vertical 4" stack. Just as I have never had to do it with a 2" pipe in a 4" wall, which would have the same problem, if it were a problem in the first place.

Wally Hays
08-01-2010, 04:47 PM
IPC wants simpson ties top and bottom on exterior or load bearing walls because......... If there is a fire in the house that portion of the wall can be weakened bu the fire and when the fire department puts the water to the exterior it can blow the wall in and crush or trap fire fighters that may be inside. I know it's a long shot but apparently it has happened more than once.

08-02-2010, 06:19 PM
I failed an inspection for the very same reason, when I questioned the inspector on this He stated I know you guys have been doing it this way for ever but now they require a 16 inch long plate with 8 16 penny nails on each side. This is to keep the top plates from pulling apart, if the house has exterior plywood installed the plate is not needed