Hi! I want to reroute my drain so that it is not below the joists to finish the ceiling in the basement as high as possible. Notching one 2x8 joist at the bottom would do the trick. It isn't up to code to do it but I have old notches in other places, and it's only one joist, it spans about 20ft (with a beam in the middle) and the notch would be around 4ft from one side. Is there a way to reinforce the joist before/after notching it a little less than 2 inches?
Notching bottom of joist for 1.5'' drain pipe
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wwhitney
In the Trades
Terminologically, the span would be the distance between the supports on either side. If the beam is in the middle, then that would be 10 ft or less, and I'd suggest getting an exact measurement from face of support to face of support (length of the portion of the bottom of the joist you can see).
Is there no way to raise the drain even more, so that you can go through a drilled hole? For the US building code, the allowable hole size is 1/3 the joist height, but the hole has to be at least 2" clear from the top and bottom (so on a 7.25" high joist, the middle 3.25" can have a hole up to 7.25/3 inches in diameter). I vaguely recall that the Canadian building code might use D/4 instead of D/3, in which case this wouldn't work (7.25/4 < 1.9).
As for notching, I'd suggest checking your building code's prescriptive span table, and determine if there's a grade and species of wood 2x6 where the allowable span exceeds the span you have (depends on the joists spacing as well). Then you could sister the 2x8 along the full length of the span (for good measure). The question is what nailing pattern to use for sistering, you could check you building code to see if it specifies a nailing pattern for doubled joists (like trimmer joists on a floor opening). The 2x6 would probably end up with a 1/4" notch, but that's negligible as long as it's not right next to a large knot.
In theory a steel strap attached to the bottom of the joists over the notch would restore its capacity, but designing the strap size and fastener size and pattern would require an engineer. And installing the strap so that it doesn't have any slack would be challenging.
Cheers, Wayne
Is there no way to raise the drain even more, so that you can go through a drilled hole? For the US building code, the allowable hole size is 1/3 the joist height, but the hole has to be at least 2" clear from the top and bottom (so on a 7.25" high joist, the middle 3.25" can have a hole up to 7.25/3 inches in diameter). I vaguely recall that the Canadian building code might use D/4 instead of D/3, in which case this wouldn't work (7.25/4 < 1.9).
As for notching, I'd suggest checking your building code's prescriptive span table, and determine if there's a grade and species of wood 2x6 where the allowable span exceeds the span you have (depends on the joists spacing as well). Then you could sister the 2x8 along the full length of the span (for good measure). The question is what nailing pattern to use for sistering, you could check you building code to see if it specifies a nailing pattern for doubled joists (like trimmer joists on a floor opening). The 2x6 would probably end up with a 1/4" notch, but that's negligible as long as it's not right next to a large knot.
In theory a steel strap attached to the bottom of the joists over the notch would restore its capacity, but designing the strap size and fastener size and pattern would require an engineer. And installing the strap so that it doesn't have any slack would be challenging.
Cheers, Wayne
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@wwhitney Thanks for the detailed response! That's very informative.
I can't raise the drain enough to clear 2'' from the bottom unfortunately, it starts at the other side so with the fittings and grade it will reach just about the bottom of the joist on the side where it connects to the stack.
Got it about the beam, I can actually notch it really close to the beam then, close to where it's already sistered:
Right there below the wires would work. I could move the wires elsewhere and reinforce the hole if it's too much material missing.
The 3'' pipe would be moved inside a future wall (that's the stud in the middle of the picture) almost perpendicular to where it is now and the 1.5'' pipe that the notch is for would go through the joist then down inside the wall and connect to the 3'' similar to how it is now.
Also note the joist is not nominal, it's about 7.5'' wide.
I can't raise the drain enough to clear 2'' from the bottom unfortunately, it starts at the other side so with the fittings and grade it will reach just about the bottom of the joist on the side where it connects to the stack.
Got it about the beam, I can actually notch it really close to the beam then, close to where it's already sistered:
Right there below the wires would work. I could move the wires elsewhere and reinforce the hole if it's too much material missing.
The 3'' pipe would be moved inside a future wall (that's the stud in the middle of the picture) almost perpendicular to where it is now and the 1.5'' pipe that the notch is for would go through the joist then down inside the wall and connect to the 3'' similar to how it is now.
Also note the joist is not nominal, it's about 7.5'' wide.
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Looking at just the ABS pipes here, you have two santees facing each other. If those are drains going into the larger pipe below, those should have been wye fittings.
A wye off to the side with a long turn 90 to pick up the drains from above. You don't have the amount of space need to use the proper fittings when the fittings are facing up.
I see a non-wrapped rubber coupling. We have to use a wrapped or shield coupling to prevent the moving of the joint over time. I've pulled out some badly deformed rubber couplings before.
A wye off to the side with a long turn 90 to pick up the drains from above. You don't have the amount of space need to use the proper fittings when the fittings are facing up.
I see a non-wrapped rubber coupling. We have to use a wrapped or shield coupling to prevent the moving of the joint over time. I've pulled out some badly deformed rubber couplings before.
wwhitney
In the Trades
Your picture doesn't show sistering, it just shows the lapping of joists at the girder.
And your notch should definitely be away from any existing holes, such as for the wires. Plus if you are reinforcing it with a 2x6 (did you check the building codes? https://www.buildingcode.online/1822.html), you want the notch far enough from the end of the 2x8 to provide good connection between the 2x6 and 2x8 on both sides of the joist. So I'd guess about 2'.
Cheers, Wayne
@Terry
The left joist is a single piece of wood from one end of the house, and the right one goes from the other end of the house up to where it ends in the picture. I think that qualifies as sistering but not sure.
The left joist is a single piece of wood from one end of the house, and the right one goes from the other end of the house up to where it ends in the picture. I think that qualifies as sistering but not sure.
wwhitney
In the Trades
If each piece of wood ends at the girder (or just past it), that's not sistering. (Well you could say that it's sistered at the 1' or so of overlap, but that's not useful). If the left hand joist is 20' long and extends over the girder to the far wall, then the right side is sistered. But that doesn't help you as far as notching the left side shown in the picture.
Cheers, Wayne
That's a 90 on the left, not another santee (if I understand what you're saying). I'm replacing this section and will definitely use a wye though. I hear you about the rubber coupling, I'll try to find a shielded one of the right size.Looking at just the ABS pipes here, you have two santees facing each other. If those are drains going into the larger pipe below, those should have been wye fittings.
A wye off to the side with a long turn 90 to pick up the drains from above. You don't have the amount of space need to use the proper fittings when the fittings are facing up.
I see a non-wrapped rubber coupling. We have to use a wrapped or shield coupling to prevent the moving of the joint over time. I've pulled out some badly deformed rubber couplings before.
I had to use a non-wrapped rubber coupling elsewhere but it was some kind of old 1'' pipe and it actually fit entirely in a piece of 1.5'' ABS pipe so I did that and put the coupling (which is also not the standard 1.25''x1.5'' one but fit the 1'' pipe) on top of them so I hope it will be fine.
Right. What if I notched where they overlap through both of them (that would be right at the corner of the right joist)?
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The vent 90 on the left can't be used as a waste fitting. What is draining into that?
wwhitney
In the Trades
As I believe I mentioned, for a sister to be effective, it needs to extend at least 2' beyond the compromised area on both sides (and have an appropriate fastening schedule on each side of the compromised area, which is one detail I don't know how to specify). Since the right joist does not extend 2' past the girder on the left, the right joist can not serve as a sister for your notch on the left joist.
The basic answer to the OP is "you can't notch a 2x8 2" deep". IF you confirm that a 2x6 would be sufficient for the span, then you could reasonably use a sistered 2x6 to reinforce your notched 2x8. The issue there is that a notched 2x8 may be weaker that a 2x6, because of stress concentrations in the corners of the notch, and because grading rules require that knots be a certain distance away from the edge of the joist, which wouldn't necessarily be true of the notched 2x8. That's why you'd need an unnotched 2x6 as your sister.
I guess if the unnotched 2x6 sister extends over the girder and has blocking underneath so that it bears on the girder, then you could have a notch in the 2x8 closer than 2' from the end of the 2x8 over the girder.
Cheers, Wayne
That would be the toilet. from the left there through the old pipe. the vent goes straight up to the roof, and the other pipe (the 1.5'' from the tub + sink) is also vented separately near the tub. The stack is out of frame on the right.
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Hmm that sounds complicated, but I don't actually need 2'', the pipe is 1.875'' which is exactly 7.5'' (the width of the joist) divided by 4. And I could do a little less too and finish the ceiling in a way that still hides the pipe.
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