Looking to move a toilet in an upstairs floor. The existing toilet is against the side of the house. There is a soffit that runs vertically from the upstairs directly into the basement (the 3 inch sewar PVC is boxed in within the soffit). I plan to reuse the line.

in order to connect the new toilet location with the existing line, it would need to run thru 3 rafters, that appear to be 2x8's. I've seen pictures where that is ok, and I've also read the max boar is slightly less than 3 inches.

'sister' the rafters PROPERLY on BOTH sides by glueing and screwing 1" plywood at least 30" long then drill away but NOT, repeat NOT, on the 'edge' of the rafters

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

remember the pipe must pitch downward.
ideally the middle rafter hole will be dead center while the others will be 3/8 up on one and 3/8 down on the other

There is a limit on the diameter of the hole as well as the location of the hole. The hole diameter cannot be more than 1/3 the depth of your rafter/joist. If 2X8 that is 7-1/4" in depth, 1/3 of that is 2.4" actual diameter. In addition, the edge of the hole cannot be within 2" of the top or bottom edge. This means you can only drill a 2.4" hole within 2" from both edges, probably not going to work for a 3" toilet pipe with an OD substantially bigger than 3".

You might want to look into Simpson heavy duty 2X triple reinforcement stud shoe to see if they have something for your toilet pipe size.

that is PRECISELY why the rafters must be 'sistered' first

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

sistering in this case won't help a lot. 3" PVC's OD is 3.5", and because of the pitch, the hole needs to be bigger for some wiggle room, most likely 4". That's more then 1/2 the depth of that joist/rafter that significantly weakens that member, now you have three members in a row that is weakened the same way. Putting a plywood sandwich on one side of the member will help with reducing the shear stress, but that plywood is also going to be weakened by the same hole. I think three stud shoes will work better.

The other way is to introduce cross members. Let's say you have rafters 1 2 3 4 5 in a series, and the pipe needs to run through rafters 2 3 4. You double up the rafters on 1 and 5, then cut rafters 2 3 4 for the pipe, then connect new 2x8 from rafter 1 to 5 on both sides of the pipe, then use joist hangers to reconnect the cut ends of rafter 2 3 4 back onto the cross members.

Sister LVLs next to the joists. They can be bored up to 2/3 the depth.

the point is to 'sister' properly - ie. REINFORCE


? how ?


an engineer BEFORE the permit is obtained would not be a bad idea



! surely the OP will be obtaining a permit BEFORE structural modification ?

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

[youtu.be]

[youtu.be]

[#$%&]

[buildingadvisor.com]



Edited 2 times.