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Unread 10-18-2021, 07:58 AM   #1
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Mud Bed in Between joists - house built 1905

Hi all - I am new the forum here. I enjoy reading previous posts and find lots of useful advice. However, I figured I would post something that has not completely been covered in previous posts.

We bought a house, built 1905, in the suburbs of Philadelphia. The second floor full bathroom was leaking during showers and I realized that the tile had cracked on the surround in several places and that there was a slow leak from the plumbing connected to the shower. That, mixed with lackluster style, led us to a tearout and redo.

We plan on putting essentially the same bathroom back, but with better tile, new tub, new toilet, and new sink. Layout stays the same though.

During tearout, I learned that the floor tile had been layed over the joists and in between the joists, a mudbed.

I am wondering two things:

1. Based on pictures and description, can I tile over the existing mud bed? Is this process as straightforward as it sounds, or am I prepping mud with something before thinset & tile?

2. Assuming I do not tear out the mud and replace with plywood, what do I do about the bathtub placement? I initially planned to place new tub over a sheet of ply and mortar. But, since there is no mudbed in between joists under where tub is placed (and nothing to support a bed there currently), what is the best way to navigate this placement?

3. There is a radiator pipe that looks as though it was laid after the mudbed was down, as shown in pictures, can how do I level this if I do not tear mud out?

4. Any other advice, based on pictures, great appreciated.

Thanks in advance!
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Unread 10-18-2021, 10:59 AM   #2
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Wow, interesting. I'm in the suburbs of Philly too, but not working with anything as unconventional as that.

I would think your path forward involves putting down a new plywood subfloor over top of the joist/mud structure and then tiling on top of that - in essence replacing the mud-set tiles with a ply subfloor which you can then tile. The thickness of the old floor leaves you room to work with. Depending on how flat things are, it might be less work to use the dry pack technique to flatten the floor for tile, after putting down the appropriate subflooring. Your tub would also then be set on mud over the new ply subfloor.

You may want to seriously weigh your options as far as re-routing some of that radiator plumbing - could make things easier and improve the tidiness of the end result.

I'm not a pro, I'm sure others with more expertise will chime in.
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Unread 10-18-2021, 12:54 PM   #3
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Hoping someone will come and also explain how that floor supports that kind of weight from all that mortar. I don't understand it from looking at it
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Unread 10-18-2021, 01:15 PM   #4
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4th photo shows boards between the joists, maybe resting on cleats, over which the mud was installed.

I don't have any experience dealing with something like that, but I don't see any way around removing it all. I do see there is some water supply plumbing that was buried in the mud, and it does look like it's deteriorating, so that's going to need to be addressed. No telling what other issues will be revealed when the between-the-joist mud is removed.
If I recall correctly my memory is excellent, but my ability to access it is intermittent.
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Unread 10-18-2021, 04:25 PM   #5
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Thank you for your replies. Really appreciate everyone's time looking and answering. So, it looks like the general consensus is to chisel out mud bed.

I am good with that.

I was thinking that, after I do that and address plumbing issues, I can sister joists with more standard 2x6s/ 2x8s and that would account for height. From there I can do the typical ply and cement board and then tile. But that is down the road some at this point.

Thanks again and I will provide update pictures in here once I make progress.
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Unread 10-18-2021, 05:08 PM   #6
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In the past we've done many floors like that but we stapled tar paper and lath down first. So there's only one way I'd do it, take it all out and mud it back.

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Unread 10-18-2021, 05:32 PM   #7
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While you've got things apart, I'd want to also get rid of any galvanized piping.

Had you considered changing the heating in that room to radiant floor heat? It would take a separate zone that might not be feasible and a lower water temperature, but would give you some more room as the radiator would go away!

To get the height back, assuming you do want that, a layer of ply on the joists, then a layer of foam, then something like Bekotec would let you get your elevation where you want it.

May all be more than you want to tackle, but a warm floor and the extra space without the radiator may be worth it...you could consider a heated towel rack in its place!
Jim DeBruycker
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