Cutting, Drilling, and Notching 2" X 8" Floor Joist for 3" Waste Line & Joist Support

[Hammer]

Can I run a 3" waste line through existing 2" X 8" floor joist using some kind of support? I want to renovate my upstairs bath, which sits on 2x8 joists at 16" o.c. I'd also like to swap the position / sides with its existing location to the other side of the room. Doing so I would have to notch the existing 2" X 8" floor joist to accommodate the new 3" waste line.

I've see they make joist notch repair kits from steel plate designed to restore the strength of the floor joists from over cut. They are expensive ($80.00 ea) are there other ways to reinforce the joist?

It would be difficult to sister another 2" X 8" up against the existing joist without a lot of additional work. The new line would be 20" away from the end of the joist at the outside wall.

Also with is the minimum fall for a toilet waste line before I have trouble?

 

[dmmsr]

Notching is highly not recommended. You want to drill holes. If possible drill to center as much as you can of course dropping for pitch.

For 3 inch and smaller it is 1/4" per foot.

4 to 6 inch is 1/8" per foot.

 

[Hammer]

Notching is highly not recommended. You want to drill holes. If possible drill to center as much as you can of course dropping for pitch.

For 3 inch and smaller it is 1/4" per foot.

4 to 6 inch is 1/8" per foot.

This is a finished house......I would have to cut a hole in the exterior wall to push it through the hole. Looking for another solution.

 

[dmmsr]

This is a finished house......I would have to cut a hole in the exterior wall to push it through the hole. Looking for another solution.

Why through the siding?

If you drill a hole you can always notch it wider. You will have to put short pieces a use couplings.

 

[MicEd69]

To answer your question, yes there are other ways to reinforce your joists. I'm a Professional Engineer and have done this many times. But it does require calculations specific for the size of the amount of joist to be removed. To install reinforcing plates, including those universal plates, you need to support the joists on each side of the notch before you cut it. Those temporary supports are required to remain in place until the reinforcing plates are totally installed with all screws or bolts, which usually means until after the plumbing is installed.

Depending on the depth and length of the notch and the size of the joist, I've used various widths of 1/4" thick plate, various angle iron sizes, 2"x1"x3/16" channel, C3x5, etc. I also like to use bolts whenever possible rather than screws. If screws are used, they need to be structural screws, like Simpson Strong-Tie #10 x 1-1/2-in Mechanically Galvanized Strong-Drive SD Exterior Wood Screws. And the number and placement of bolts or screws are important.

I would expect that unless you have a friend who is an engineer and capable of doing those calculations for free or a case of beer, those universal reinforcing plates are the least cost option for you.

 

[hukre]

Do you have to go through just one 2 x 8 ore more than one? This makes a big difference.

 

[Hammer]

Do you have to go through just one 2 x 8 ore more than one? This makes a big difference.

I have to go to the other side of the room....about 10lf.................so that's like (7) 2 X 8's

 

[psklein578]

Looks like you need to create a chase for the drain. That would require cutting a section out of each joist and putting beams on the cut ends of the joists. The beams would have to be well supported on each end of the chase.

 

[Hammer]

Looks like you need to create a chase for the drain. That would require cutting a section out of each joist and putting beams on the cut ends of the joists. The beams would have to be well supported on each end of the chase.

Are you talking about heading off to allow for the drain assembly like this?

 

[MicEd69]

Are you talking about heading off to allow for the drain assembly like this?

It sounds like that is what psklein578 described. The drawing you show is a classic way to install a toilet when the drain hits over a joist. However, boxing in a 10-foot section of floor to make a chase cannot be done using just a picture. psklein578 indicated, "The beams would have to be well supported on each end of the chase." That may mean it needs more than what's shown as a "double trimmer" in your picture, which would have to span the entire length of the joist you are sistering even if it will suffice. And just as important would be the connections of the cut joists to the beam. Simply nailing into the end of the joists and/or toenailing the joists into the beam will likely not be sufficient. And the beam will likely need to be more than a double 2x8.

 

[dmmsr]

Definitely need an engineer to figure out load calculations if you're going to alter the beams. Unless you have two load bearing walls on each side. This is something not worth testing and trying to figure out on your own.

 

[psklein578]

Are you talking about heading off to allow for the drain assembly like this?

That's not exactly what I was thinking. I thought you were wanting to run the drain perpendicular through the seven joists. As others say, you would need an engineer to figure the size of the supporting beams. I drew a sketch of what the basic idea.

 

[dmmsr]

That's not exactly what I was thinking. I thought you were wanting to run the drain perpendicular through the seven joists. As others say, you would need an engineer to figure the size of the supporting beams. I drew a sketch of what the basic idea.

I had to do some supports in my house with the help of a general contractor friend. We did a recessed beam. Kind of what it looks like you want to do on both sides. With what your doing it seems like you would need to have 2 beams calculated and installed over load bearing supports going all the way down to basement /slab.

 

[hukre]

How about running the pipe below the 2 x 8s and make a nice looking soffit to hide it.

 

[hukre]

Also keep in mind that your pipe of about 10 feet in length has to be sloped 2½' from one end to the other (¼" per foot).

 

[frontporch]

Very cool joist support. I have not seen that before. I would imagine besides cost, there would be challenges installing that support, like you probably need to have enough confidence that you can support the joists during construction and put in that support in a way that returns the joists to their "pre notched" orientation. (I am guessing you initially install the plate before you cut and reuse the holes you made when reinstalling) Also, getting some of those screws into the top of the support, right below the subfloor might be a lot harder than it appears.

My unprofessional opinion is to look into all options that do not require a joist to be cut, or worse notched. If you have a typical house, it was built to the minimum specs and a span of 12' practically overwhelms a solid 2x8. A good rule of thumb is to stay away from the edges as the center of the joist isn't nearly as important, structurally. I spent a lot of time in my house running a 2" drain pipe with the correct slope over a distance of about 8'. At the center of the run it was pretty darn near the center of the joist. I wouldn't have considered a 3" pipe. Also the issue you mentioned is threading the pipe without a lot of connectors. Its impossible... unless you have that hole in your house.

Any good suggestions, in my opinion, would require more information.
What is underneath on the first floor in terms of walls?
Can the drain be run along the top of a wall and hid in a soffit was was suggested, or does it run through the center of the room?

It may be outside the scope of this forum, but I am interested and somebody might be able to suggest an alternative if there was more information.

 

[MicEd69]

you probably need to have enough confidence that you can support the joists during construction and put in that support in a way that returns the joists to their "pre notched" orientation.

You have to build two parallel temporary "walls" under both sides of the cuts or notches, even if you are using the notch support plates that Hammer shows in his first post. And those "walls" must remain in place until the joists are back to structural integrity. Generally, those temporary walls can be done pretty easily with 2x4 studs located under each joist and 2x4 top and bottom plates for a normal house.

What psklein578 has suggested is a standard way load bearing walls are removed with a "hidden header" times two. LVLs are wonderful and in that approach, the temporary walls could be removed allowing the plumbing work to be done in an "open" space. But it would require an engineer to confirm a 7 1/4" LVL would work for this approach. And as dssmr said, an engineer also needs to confirm the loads that are being transferred to the ends of the LVL are supported "going all the way down to basement /slab." But just a small correction there, "basement/slab" should read "foundation". A basement slab has no structural support capability. It is only an 4" slab of unreinforced concrete.

 

[frontporch]

The chase in the ceiling is a big project but a great idea and very cool
I was just wondering if simpler options should be explored. In my house I chose to drop the 3” pipe into a non load bearing wall to create a “wet wall”and bring the pipe into the basement without needing to cross any joists

 

[hukre]

One more idea: Put a macerating toilet in your new bathroom and instead of having to run a 3" discharge, it will require only a 1" or 1½" discharge pipe which you can run at the center through the 2 x 8s.