Notching/drilling rafters

[PATERLEY]

Hello, I’m on a job taking out a drop ceiling and converting to a vault. There are currently 2x12 rafters 24 OC spanning 12-14 feet at a 6:12 pitch and 40 snow load.

Problem is, there is a 2” vent that penetrates through right in the middle of my vault, with the existing pipe below the rafters

I’m hoping to either notch the bottom (easiest option because of spray foam insulation) or drill a hole in the middle of the rafters to run a new vent. Considering the span and loads I feel like either would be okay, but am I missing something? Could also reinforce the bottom of the notch with strapping if needed.

About 3 rafters in total will need to be modified.

I appreciate any and all help.

Pat

 

[milkshakelake]

I'd be wary of drilling into structural members. Just looking at the picture and not having more info, it might be to tie the roof on both sides for lateral thrust, so it looks like a structural member. If you can move the vent down and avoid drilling, that would be the best option. If not, I'd hire a structural engineer to evaluate it, because I see you're industrial and it's not exactly the same (not to knock on you, it's just a suggestion, and sorry if that suggestion doesn't apply to you). If you're going to evaluate it yourself though, I'd check the rafter for the reduced section (say if it's 11.25" deep and you're taking out 2", evaluate it for 9.25" effective depth in tension and flexure).

However, I've seen issues with roof thrust, even when nothing is modified. I'm just not a big fan of drilling through members. If you want to be conservative, I'd drill through the bottom or top only but sister it with a 2x10 to be on the safe side. The sistered joist should be well connected to the supporting studs.

The issue is that wood is a natural material and therefore is subject to shrinkage and nail slip. I know shrinkage is not a major concern in the longitudinal axis, but wood just tends to shift and move over time. That's why I'm wary of the whole thing. It's just a liability and serviceability thing, not a life safety issue.

 

[JAE]

There are maximum limits to notching flexural members (per the NDS wood code via the IBC/IRC).
If you don't know what those are, then hire a structural engineer as milkshakelake suggests.

Wood has grain lines which, around a cut notch, could split the member up at a longitudinal angle and fail the entire member...thus the limit on the notch depths and locations relative the span length.

 

[SWComposites]

Its just plastic pipe for a vent. Cut it apart and reroute the vent pipe. Do not cut or notch the rafters or joists.

Wait, you want to reroute the vent thru the middle of the rafters??? No. Just no. Move the vent location in the roof.

 

[dauwerda]

Why is everyone acting like this is crazy?
Here is the relevant code section that you would need to follow:

https://codes.iccsafe.org/content/IRC2021P2/chapter-5-floors#IRC2021P2_Pt03_Ch05_SecR502.8.1

If it were me, I definitely wouldn't notch, even if it did fall within being allowed per the code section below (though this would be the tension side of a member greater than 4" in depth, so it would not be allowed).

 

[StrucPatholgst]

You should get a structural engineer to look at that framing. From the little I can see, those horizontal ties are in tension and holding the walls in place. Removing them would be no bueno without installing a true ridge beam.

 

[PATERLEY]

Hey everyone, I apologize. The info I gave was not complete and incorrect in come cases.

The ridge beam is indeed structural (6x14). No collar ties or anything like that for the rest of the rafters that are in place. The span is only 7 ft for the 2x12’s. With all the info I have, I think boring into the middle 3rd is my best bet unless anyone can think of a reason not to… I would really like to avoid going into the roof and drilling a new vent, especially if this is going to be structurally sound. Thanks!