Are wire mesh and thinset jobs still acceptable?

We had some sloping issues in the master bath of our newly built house so the tile guys ripped up half of the tiles to get to the plywood subfloor to see what was going on. I was a little surprised to see what looked like some wire mesh and thinset on top of the plywood. No backer board or any membrane. So I started doing some online searching. I guess this is called a Jersey Mud Job? And from what I can tell, it's an old and not very reliable way of laying tile--especially in a bathroom. Is this type of tile installation still acceptable these days?

I'm going to try and attach a picture of what I'm talking about.

 

If this is in the shower then there MUST be a membrane. Thinset, tile and grout are not waterproof.

If this is the floor of the bathroom then a membrane is not required because it isn't soaked in water. The wire mesh should have been screwed to the wood subfloor and there is a minimum thickness it can be. Too thin and it will crack. It is the old school way of doing things because it's slow and labor intensive but it can work very well and last for decades.

Make sure your tilers do not put thinset directly down on the wood. They need an intermediate tile backer like cement board or Hardie Backer.

 

Yeah that's not good. That's an OSB subfloor, not plywood, and that's even worse. One of the problems is that subfloor is exposed to the elements during construction, so it can sometimes be in good shape... sometimes not. There can be dips due to water ponding on the deck, and seams can be swollen and raised.

Here is a discussion on the topic.

https://www.doityourself.com/forum/w...r-3-4-osb.html

Czizzi will probably be along to give his input. There are standards for laying ceramic tile, and he can address that better than I can.

But the mortar in the mesh does look thin... practically non existant. I don't know how that could possibly isolate the plywood seams. Plus if that is 3/4 tongue and groove OSB it doesn't meet the minimum 1 1/4 thickness required under floor tile.

 

Yes, this is the main bathroom floor only. Not the shower.

There's absolutely no cement board or Hardie backer board involved here. Nor does it appear that the wire mesh has been screwed to the subfloor anywhere either. From what I can tell, it appears that the mesh was laid upon the bare plywood, then thinset on the mesh and then the tiles were laid.

 

I stand corrected. Shows how much I know. Thanks for the additional info and link. I have some more studying to do. I'm also unsure of how thick the OSB is. I'm going to see if I can find out when I get home.

 

If there is a heat register in the floor, remove it and examine the subfloor thickness behind the ductwork.

 

That's a good idea. I'll give that a check. Thanks

 

I was just able to check. It's 3/4 in OSB.

 

Judging by how clean the floor came out after tear out, nothing stuck to the floor. The mesh had to be adhered in some way. My guess is they installed the mesh, floated some self leveling compound on top and they installed thinset mortar and tile.

Old school mudbeds worked as follows: Tar paper (isolation membrane) was put down, wire lath was installed, and then a minimum 1" - 1 1/4" thick mudbed was screeded on top. The tar paper allowed the wood subfloor to expand and contract and not transfer to the tile. The thickness of the mudbed allowed it to stand on its own. Floors made this way last for decades. I'm currently installing a custom shower floor based on this theory, so it is still done today.

My issue with your set up is that the subfloor may not be strong enough at only 3/4". We know nothing of the unsupprted span of the floor joist, nor their size or spacing. The thin layer of mesh and cement add nothing structurally to the mix , so any deflection either in the joists or between the joists will cause loss of bond. and or tile cracking or grout cracking. The fact that you are using large format tile probably is to your benefit with this set up. Smaller tile or mosaics would probably already been cracking.

 

Yeah, we are using 12 X 24 tiles. I don't know the exact spacing of the joists. But, if it helps, here's a picture of the sub floor looking up from the garage--pre drywall. The red arrow is pointing to the corner of the bathroom where they pulled up the tile.

 

It's very unusual for a truss floor to not be level. Did you ever discover the cause of the sloping floor?

What is the spacing between your floor trusses? They look further apart than 16" maybe yours are spaced 19.2" or even 24"? That would be a further warning sign with only 3/4" thick subflooring.

 

The main reason of the floor slope appears to be that the framing on that side of the house just appears to be slightly higher for whatever reason.

I'll see if I can get up there with a ladder and measure between the trusses.

 

This is a "jersey mud job" which is diamond lath stapled to the subfloor, then thinset applied, then tile installed. It's not a real mud job and is not a acceptable method for tile installation, but is common in new construction in my area (i've tore out a few) I have seen some installations last, and some not. But the fact remains, that its not a good installation and is prone to failure, just a matter of time.