Joist Obstructing Shower Drain & Very Unlevel Sub Floor [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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07-03-2019, 08:18 AM
I have two problems. A joist is obstructing where my schluter shower drain needs to be. Secondly, the floor is 1 ⅛ out of level. So I sistered new joists to the old ones to help Level the floor as well as reinforce the strength of the old joists. I have not bolted/screwed the new joists together yet. Nor have I added the blocking along with the joist hangers. Before doing all of this I wanted to verify that I am headed in the right direction with you all. [emoji12] When I complete adding the joist hangers, gluing & bolting the new joists to the old Joists, & adding the blocking, I believe I should not only have a new level subfloor for my schluter pan, Ditra, & Floor/Shower Tile, but also will be able to notch ½ the obstructing joist to make room for the drain.. am I correct? Any advice or recommendations will be highly appreciated!! Thanks!


Room/Material Specs
89” x 89” Bathroom
23/32 OSB Subfloor
½ inch Hardibacker over OSB
Schluter Ditra for floor tile
Schluter AllSet Thinset
12 x 24 inch floor tile
Mosaic Shower Floor Tile
Schluter Shower System
Two Shower Curbs
3 Schluter Shower Panels for walls
38” x 60” Schluter Shower Pan (Centered Drain)
12 x 6 beveled shower wall tiles

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07-03-2019, 08:47 AM
Welcome to the forum, Gary. :)

How did you sister the joists if they're not glues and screwed to the existing ones?

What you can do is box out that area where the drain will go and attach the cut ends of the obstructing joist to the blocking you've added.

Regarding your floor, is there a reason you plan on using 1/2" Hardibacker? Unless you just want the extra height, you can use their 1/4" version, or any of the other cement boards that have a 1/4" board.

And you also listed Ditra for the floor. That would be redundant if you have a cement board down. You should choose one or the other, but you don't need both.

07-03-2019, 09:18 AM
I really appreciate your input. Thanks! As of now I haven’t glued or screwed the joists yet. That is what I will be doing today. I figured it would be wise to post before doing so. As for the osb combined with hardibacker, I needed the height to match the flooring in the master bedroom. I also thought that doubling the subfloor would help strengthening the floor. I choose backer board because it was easier to handle than trying to cut & carry ½ OSB. Is using the two together a bad thing?

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07-03-2019, 12:48 PM
If you want more strength in the subfloor, use plywood, not cement board. If you just want the extra height, there's nothing wrong with using 1/2" vs. 1/4".

What I was pointing out as redundant was the use of any cement board along with Ditra. It's like wearing suspenders and a belt. Not to mention it costs a lot more.

07-06-2019, 09:29 AM
I left him alone for 5 minutes & this is what I came back to. The joist has a span of 17 ft. His cut is 7ft from the end. It is a 2x8. He told me this is a standard & acceptable notch that won’t affect the strength of the joist. I think he’s full of baloney. Who’s right?

07-06-2019, 09:40 AM
That joist is indeed butchered and has lost nearly all of its load capacity and stiffness.

Not at all acceptable and completely illegal. Basically a verical rip in a location where no notches are allowed at all.

07-06-2019, 10:05 AM
Welcome, Gary. :)

I've combined you with your original thread on this project so folks can see what's been previously asked and answered. Please keep all your project questions here. A moderator can give it a more generic title any time you'd like to suggest one.

I'm not able to tell if your new sister joists are supported at the ends, nor can I tell what size joists you have or the unsupported span. That information will be important here.

A better photo showing some perspective might help. I can't tell if your damaged joist is where you'd previously indicated your drain would be or perhaps somewhere else?

While no notching is permitted in the center third of a floor joist, what you appear to have is a reduction of your joist by half its thickness, which wouldn't be quit the same, but still problematic. Depending upon how you did your sistering and the material and span, all might not be lost.

Shooting the plumber would still be a good option to protect the next customer. Suing him might be a more effective option for your benefit, depending upon whether you want to spend the time and money.

My opinion; worth price charged.

07-06-2019, 11:42 AM
Your sistered joist will have save you, IMO, assuming you glued and screw it to the original joists.

Re the ignorant plumber, I’ve included a link to the notching and boring section of the IRC.

As you can tell from this ( recent post, you’ll see cleaning up after and ranting about plumber induced structural headaches is a common theme.

Fast eddie part deux
07-09-2019, 06:44 AM
He told me this is a standard & acceptable notch that won’t affect the strength of the joist.

It is normal for plumbers to remove anything in their way and claim it is normal and of no consequence. That joist now has almost no strength.
My opinion ... i would have moved the drain 2" to the side to clear the joist, and just lived with the off center drain. At least i would have been able to sleep at night knowing that i had not butchered the strength if the floor structure.