Drilling 2x8 rough sawn joists for 3" DWV pipe for toilet drain

[ColinMcM]

Will this pass inspection (Hartford, CT) if I sister the joists with plywood, construction adhesive, and nails around the holes centered in the joist width, leaving 2" above and below the holes? I need to drill through five 2"x8" joists to get one of my new wall mount toilets to tie into the new stack I'm adding. Wondering if I can drill out the middle 4" of the (true) 2x8 to pass the toilet drain through. If not, what would be a good way to box out a chase in the joists to provide space for the drain line pass perpendicular to those 5 joists, perhaps using joist hangers and doubling some joists? Can't put the stack anywhere else because there is a flush W8 steel beam going in the joist cavity nearby to create an open floor plan for the kitchen/living room on ground floor. Thanks in advance for your help. I'm going to have a plumber do this, but I just need to know enough to make sure it gets done right.

 

[DIYer123]

I would doubt it rule of thumb is max middle third. so 8/3 = 2.66.

Likely need to box out.

What's the span of the joist and where approximately is the box out in the span, end third or middle third? Is there anything heavy on the span such as a tub? (note not just over the potential box out area, but over the entire span of the members you are going to cut.) Also confirm box out would need to be 96" span to allow removal of the 5 joist sections.

 

[Sponsor]

 

[wwhitney]

Drilling 3.5" holes in an 8" tall solid sawn joist is not prescriptively allowed. You could find an engineer who could design the proper reinforcement, then it would be allowed.

As for heading off some joists, we'd need a floor plan showing the beam and all the supports, the joists and their direction, and the locations of the toilet and the stack.

Cheers, Wayne

 

[Jeff H Young]

not legal but , that doesent mean you cant do it. Just because inspector sighns the card dosent mean anything either. Sounds exessive to me but depending on span and load might be ok

 

[ColinMcM]

Thanks for your replies guys. Here is a picture of another idea. If I can run my 3" PVC drain line in the web space of my W8x40 Steel I-beam, I can avoid drilling joists. Then I will need to use top flange joist hangers that will be welded to the top of beam instead of the face mount hangers shown in the drawing. Is this crazy? The yellow in the drawing represents plumbing, the green is the steel beam, and the brown is solid sawn wood joists and hangers.

 

[Reach4]

1. How about going horizontally thru the wall rather than down from the toilet?

2. How about using 10 inch beams and 3 inch (3.125 od) copper drain pipe?

3. 9.5 inch I-Joists could allow pvc-sized holes I think. See https://lpcorp.com/media/1381/lp-solidstart-i-joists-residential-technical-guide-canada.pdf page 14.

4. If putting copper in web of steel beam, you need electrical insulation, which can be thin.

5. If putting pvc into web of steel, remember the OD of the fittings on each end. Same with copper, but copper pipe and fittings are both smaller.

 

[Jeff H Young]

sounds a little crazy to me, Welding a sheetmetal joist hangar to a beam? Is this standard practice and no engineering required? If I remember right welding on certain parts of an I beam are prohibited.
I saw a guy sister up steel plate to the side of week undersized joists and through bolted it on "this old house" 20 years ago I thought it was pretty cool but unless its engineered I wouldnt think it such a good Idea.
Im pretty good at ripping out wood but not my job or expertice to really know or be an expert at structural repair, that said we have all been involved in situations like this , Ive headed out joists but this is pretty serious stuff , Id consult with a structural pro and please share what info you learn from a man with 30 years structural experiance as opposed to us who many are simply hobbiests DIY'ers.

 

[wwhitney]

Is this new construction, or is it just that you have everything opened up enough to change the wood joist/steel beam connection? The usual/existing connection is to pack out the web with 2 or 3 2x8s each side with through bolts holding the 2x8s to the web?

How far is the toilet flange from the I-beam?

Cheers, Wayne

PS. Top mount joist hangers are a standard thing now, and some of them are weldable. "LB, LBAZ and BA may also be welded to steel headers with weld size to match material thickness. The minimum required weld to the top flanges is 2" (1 7⁄16" for LBAZ) fillet weld to each side of each top flange tab. Distribute the weld equally on both top flanges. Welding cancels the top and face nailing requirements" Simpson Strongtie C-C-2019 catalog pg 122.

 

[Jeff H Young]

Just curious is this a new house? just a re pipe? No mention why your doing this to your house? got permits? old 2 x8 rough sawn joists but hanging off steel I beams kinda wierd 100 year old stuff mixed with kinda newer. Maybe I missed something here . blue prints?

 

[DIYer123]

If it were me I would be looking to box out over welding, even if you have to triple up the three members of the box out it will be far less cost and effort then the welding. Adding the box out will make the plumbing easier to install and a cleaner run. As noted above if you have a blue print with diims it would help . Also no offense to the plumbers here but I would have a carpenter do the box out, not the plumber (I would actually do it myself as i don't trust anyone to care as much as i do to do it right.)

 

[Jeff H Young]

No offence taken Id rather my house framed by a carpenter , plumbed by a plumber and wired by an electrition. by far over a homeowner that cares, in general. That said Ive seen some excellent work done by homeowners. but they are the exception rarely does thier work exceed that of an average tradesman. but some do . almost always I find some good things because they are really trying , along with many screwups because they dont know any better some are minor errors but its almost never "professional" maybe a homeowner that really cares can build a structure better than a 20 year experianced carpenter , but Im guessing a carpenter can build a better house than a waitress , a financial planner, or a uber driver could

 

[ColinMcM]

It's an old house, we're adding the steel beam to create an open floor plan on ground floor. The rough 2x8s are the existing joists. Suppose I could change out or sister them but that would make my ceilings lower and I'd rather not. We have permits, and already had a structural engineer design the beam configuration. From what I've read the top flange hangers (BA series) are easier to install than packing the beam, and I know how to weld so that's not a worry. I'm the homeowner and also a contractor, I've built a few buildings and done plenty of remodeling but the plumbing design is what I'm trying to figure out. Just wondering if you were a plumber and looking at this problem how would you do it? Box out a chase or snake it through the beam web behind the hangers? The toilet is about 12 feet horizontally from where the stack will drop down, either way, so it will probably be minimal slope, like 1/8" per foot either way we do it. I figure the wider parts of the fittings will be no problem because they can fit in spaces between joists as needed. If I went through walls from the wall hung toilets wouldn't the carrier be in the way? That's why I was not considering that option but if there's a way to do it I'm all ears.... Thanks!

 

[Reach4]

If I went through walls from the wall hung toilets wouldn't the carrier be in the way? That's why I was not considering that option but if there's a way to do it I'm all ears....

https://terrylove.com/forums/index.php?threads/toto-wall-hung-outlet-pipe-slope.69960/

This says that horizontal is not an option, for some carriers, but you could go 45 outside of those,and then horizontal. I have no relevant experience.
https://terrylove.com/forums/index.php?threads/wall-hung-toilet-drain.77685/

https://www.zurn.com/products/building-drainage/carriers-fixture-supports/water-closet-carriers

 

[wwhitney]

The toilet is about 12 feet horizontally from where the stack will drop down, either way,

But what are the coordinates relative to the beam? Distance from stack to beam (perpendicular to beam), distance from toilet to beam, and offset parallel to the beam? For the last number you said you'd have to go through 5 joists, so it should be ~90" if the joists are 16" o.c.

Cheers, Wayne

 

[Jeff H Young]

It's an old house, we're adding the steel beam to create an open floor plan on ground floor. The rough 2x8s are the existing joists. Suppose I could change out or sister them but that would make my ceilings lower and I'd rather not. We have permits, and already had a structural engineer design the beam configuration. From what I've read the top flange hangers (BA series) are easier to install than packing the beam, and I know how to weld so that's not a worry. I'm the homeowner and also a contractor, I've built a few buildings and done plenty of remodeling but the plumbing design is what I'm trying to figure out. Just wondering if you were a plumber and looking at this problem how would you do it? Box out a chase or snake it through the beam web behind the hangers? The toilet is about 12 feet horizontally from where the stack will drop down, either way, so it will probably be minimal slope, like 1/8" per foot either way we do it. I figure the wider parts of the fittings will be no problem because they can fit in spaces between joists as needed. If I went through walls from the wall hung toilets wouldn't the carrier be in the way? That's why I was not considering that option but if there's a way to do it I'm all ears.... Thanks!

Thanks for clarifying , Personaly as a plumber Id be dropping the ball in either the owners or G.C. court I would recomend a soffit. I know you dont want to hear that but as a plumbing contractor , I cant solve carpentry or engineering issues. Ill drill out the joists no problem at owners/ gc request , If it was a freind or family I might help with beefing up some framing .I just cant do something like that and be responceable for it .
Welding joist hangars might work, but I think an engineer would need to bless it? also wont welding need to be by certified structural welder and onsite inspector? Just asking I really am uncertain. Perhaps your drawings show both options on how to install joist hangars
PS Wall hung toilets , Ive never installed in residential application, but carriers have side waste outlets as well? also a Wall hung and a wall outlet toilet are 2 differant animals . Im not guessing why the wall hung?

 

[Jeff H Young]

But what are the coordinates relative to the beam? Distance from stack to beam (perpendicular to beam), distance from toilet to beam, and offset parallel to the beam? For the last number you said you'd have to go through 5 joists, so it should be ~90" if the joists are 16" o.c.

Cheers, Wayne

Somethings in back of my mind . 5 joists to drill we run 1/4 per foot fall on 3 inch here but Ill cheat a little and go 1/4" per (16") joist if I need to so thats considered. Joists could be 18 even 24 inch on center ?

 

[wwhitney]

Yeah, with 5 joists to cross, if it's 8' that's 2" of of fall at 2%. Which would make 5-1/2" of "interference interval" out of 8" of joist, leaving 1-1/4" solid top and bottom. A structural engineer could probably make that work.

But Connecticut is on the IPC which allows 3" pipe at 1% slope. That makes only 1" of fall, so you could get 1-3/4" of unmolested joist top and bottom. Better structurally.

Cheers, Wayne

 

[ColinMcM]

Thanks Wayne and Jeff, really appreciate your thoughts. Wasn't aware of the wall hung vs. wall outlet option. We liked the wall hung with the tank hidden in wall because of the clean sleek design and a little more legroom in front of it. But maybe the wall outlet with a normal tank would work better for fitting the plumbing in. Also was just reading about washdowns and pressure assist flush ones vs. siphonic. I'm going to do some more investigating and see if I can avoid drilling the joists. Also going to follow up with the building inspector, but your comments helped me figure out the options I wanted to ask him about. Thanks again.

 

[Jeff H Young]

Thanks Wayne and Jeff, really appreciate your thoughts. Wasn't aware of the wall hung vs. wall outlet option. We liked the wall hung with the tank hidden in wall because of the clean sleek design and a little more legroom in front of it. But maybe the wall outlet with a normal tank would work better for fitting the plumbing in. Also was just reading about washdowns and pressure assist flush ones vs. siphonic. I'm going to do some more investigating and see if I can avoid drilling the joists. Also going to follow up with the building inspector, but your comments helped me figure out the options I wanted to ask him about. Thanks again.

I guess the wall hung was because you had some particular fixtures in mind and not simply for structural reasons. definately a challenge here!

 

[wwhitney]

Thanks Wayne and Jeff, really appreciate your thoughts.

Was hoping you would provide some dimensions to allow analyzing the box out option. It sounds like you need to run both parallel to the beam and perpendicular to the beam. That would make a prescriptive box out options tricky, because prescriptively you can't cross any of the framing members.

Cheers, Wayne