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# Thread: What's the max size of drain/vent pipe that I can I can put thru a 2x4 stud?

1. ## What's the max size of drain/vent pipe that I can I can put thru a 2x4 stud?

I will shortly be re-doing all of the plumbing in a small bathroom and adjacent kitchen. In order to vent properly I will need to run ABS thru several studs, then through the exterior wall top plate. What is the max size pipe that I can run through these framing members.

I am in MA, which uses a modified UPC code.

thanks,
Rick.

2. If these are studs in a NON-LOAD BEARING WALL, then you can bore up to a 2&1/8" hole in the center of the stud. If this is a load bearing wall, then you are "technically" SOL.

3. Correct. Might also be worth mentioning that this is not a plumbing code issue, but is rather covered under building codes.

4. I drill whatever size hole I need for the pipe I am using, whether it is a small water pipe, or up to a 2" waste or vent line.

5. Notching & Boring:
Board Holes: A hole not greater than 40% of the stud width may be bored in any wood stud.

Bored holes not greater than 60% are permitted in non-bearing walls and partitions.

Bored holes not greater than 60% are permitted in bearing walls provided that each bored stud is doubled and no more than two double studs are bored. In no case shall the edge of the bored hole be closer than 5/8” to the edge.

Bored Holes
Bearing Walls Non-Bearing Walls & Partitions
40% for 2 X 4 = 1-3/8” 60% for 2 X 4 = 2-1/8”
40% for 2 X 6 = 2- 3/16” 60% for 2 X 6 = 3- 5/16”

Notches
Bearing Walls Non-Bearing Walls & Partitions
25% for 2 X 4 = 7/8” 40% for 2 X 4 = 1- 3/8”
25% for 2 X 6 = 1- 3/8” 40% for 2 X 6 = 3- 5/16”

6. A kitchen sink under a window is quite common, and if I cannot bore a 1 1/2 inch hole (more than 40% of a 2x4 in a load bearing wall), then how do you commonly do it? I need to get through a single and a double stud under the window in order to get to the cavity that runs up to the top plate and in to the attic. What do you guys do?

Rick.

7. You should ask your building inspector. It seems that a lot of the time the rule is not adhered to and is overlooked.

8. I just drill it, and have NEVER had an inspector question it. A jack stud under a window is NEVER a bearing partition.

9. What I do is double the stud on the side of the window where I am running my drain pipe.

What I have noticed on a number of large homes with large picture windows over the kitchen sink is that they are running the pipe on the outside of the wall and inside the cabinets. To avoid the issue.
Michael

10. quote; with large picture windows over the kitchen sink is that they are running the pipe on the outside of the wall and inside the cabinets.

In that case, or like one I did which had 6x6 posts on either side of the window, I installed it as if it were an island.

11. OK, thanks for all the replies. I think that I can run the vent inside the cabinet far enough to get into the open wall channel, without having to create the bow vent.

rick.

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