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1.5" Drain Pipe Through 2x8" Joists - Ontario

S

StuartL

Registered User
Joined
Feb 10, 2023
Messages
6
Location
Kingston, Ontario, Canada
We're installing a new bathroom on the second floor of our house, which has 2x8 floor joists. The 3" toilet drain does not need to cross through any joists, but the 1.5" drain pipe servicing the tub and sink needs to cross multiple joists (roughly 8' run). The limitations for our build and the Ontario Building code...
  • 1.5" is required for sinks and showers with one head
  • 1.5" pipe seems to always have a 1.9" outer diameter, which would mean drilling a 2" hole in each joist
  • you can only cut a hole 1/4 the depth of the joist... 7.25/4 is roughly 1.8"
So, it seems like that's not an option.

Is there a standard solution for this? E.g. thin walled pipe, or laminating joists to allow larger holes?

Or, is there something like these products that are engineered for use in Ontario?
www.metwood.com

Joist Repair Hole Reinforcer 2810HR By Metwood

The 2810HR Joist Reinforcer allows the placement of a 6” diameter hole in a 2x10 or 2x12 wood joist and a 4” diameter hole in a 2x8.
www.metwood.com www.metwood.com
joistrepair.com

2x8 HR Floor Joist Hole Repair Kit for reinforcing joist or truss holes, route utilities right through floor joists

The 2x8 HR Joist Hole Reinforcer is the perfect joist repair kit for repairing or restoring the strength of floor joists that have been compromised due to holes, cuts, or or even cracks. The 2x8 HR can handle holes up to 4" diameter in 2" x 8" joists when holes have been cut that are larger than...
joistrepair.com joistrepair.com

We are trying to do this on a budget, so would like to avoid having to get an engineer involved.

Thanks in advance!
 
A non-standard solution would be to use 1.5" copper DWV for the cross joist run. That has an OD of 1-5/8", so 1-3/4" holes very carefully drilled would suffice. Then you'd need some banded rubber couplings at each end to adapt back to plastic.

Of course, installation of a single piece of pipe in existing joists would be a challenge. If it's adjacent to a stairwell opening or an exterior wall, you might be able to drill one extra hole and slide the pipe in. Otherwise, you're looking at using multiple short sections and soldering couplings. Or I guess you could install it like no-hub cast iron and use multiple banded couplings (Fernco Proflex 3003-150 or Mission Rubber K-150 for 1.5" copper DWV to 1.5" copper DWV).

Cheers, Wayne
 
Seems like a question for your building department. I would think with the data they provide it would be approved.
 
Even if they allowed you to drill a 1.9” hole vs 1.8” … the hole needs to be centered so you won’t be able to build in any slope.
 
Thank you, all, for the answers.

Wayne - that sounds like a very good alternative solution.

Bill - thanks - I will run it by my local building authority.

e hilton - I would be hoping to drill 2" holes allowing for some slope. Rules state no drilling within top or bottom 50mm (2 inches), so that leaves about 1.25 inches of vertical allowance.
 
I had a similar problem in renovating my house.

I ended up running the pipe below the ceiling and building a bulkhead around it. We installed tile in the bathroom and I was worried the extra deflection would cause the tiles to pop.
 
So your Candandian code is different you say!

2018 IRC figure R502.8 2x8 joist (7.25 Actual depth). Need 2-inches from the edges would give you 3.25 to work with, but only allows a 3-inch max hole noted.
 
Canadian, sorry for the misspelling, I've been worring about spy ballons this week!
 
Thanks, Pcinspector1 - we are D/4 here for max hole size, so 1.82".

tmurray - noted - I'd like to avoid a bulkhead at all costs, but it could be a fallback option.
 
I've thought up another unorthodox solution, to avoid drilling through the joists altogether:

Put the tub on a 2x4 platform to raise it up 3.5 inches, and that will allow the drain to run through the wall that will house the remainder of the plumbing, instead of through the floor.
 
StuartL said:
Put the tub on a 2x4 platform to raise it up 3.5 inches, and that will allow the drain to run through the wall that will house the remainder of the plumbing, instead of through the floor.
Click to expand...
A 2x4 platform will actually be more than 4” when you add the plywood. Regardless … i have enough trouble stepping into a tub now, can’t imagine making the stepover 4” higher.
 
Use the metal reinforcements and a hole large enough for see slope. Same hole could allow slipping on piece in rather than joints.

I get concerned when one necessary change leads to another and suddenly the plan is lost. Just trying to limit the ripple effect.
 
Thanks for the input - the easiest guaranteed code-compliant way is going to be having the tub elevated, and run the drain above the floor. I've mapped out a way so that the tub will only end up 1" higher relative to finished floor.
 
Bulkhead.
I write plumbers up on excess holes through framing members more often than I would like.

e hilton said:
Even if they allowed you to drill a 1.9” hole vs 1.8” … the hole needs to be centered so you won’t be able to build in any slope.
Click to expand...

Not up here. Not necessarily.

NBC 2015:
9.23.5.1. Holes Drilled in Framing Members
1) Holes drilled in roof, floor or ceiling framing members shall be not larger than
one-quarter the depth of the member and shall be located not less than 50 mm from the
edges, unless the depth of the member is increased by the size of the hole.
9.23.5.2. Notching of Framing Members
1) Floor, roof and ceiling framing members are permitted to be notched provided
the notch is located on the top of the member within half the joist depth from the edge
of bearing and is not deeper than one-third the joist depth, unless the depth of the
member is increased by the size of the notch.
 
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