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-   -   What is this subfloor and how do I level? (https://www.johnbridge.com/vbulletin/showthread.php?t=112177)

Kimbo 04-02-2014 07:56 PM

What is this subfloor and how do I level?
4 Attachment(s)
Hi all - new to the forum, but have been avidly reading posts here for months. I'm in the middle of a bathroom project, and need some advice on how to best level my subfloor for 12x24 tiles.

I live in a condo that is ~2005 construction. Prior owners had put down tile on top of tile. The room is approximately 6ft x 8 ft.

After removing two 2 layers of tile I'm left with a crumbly concrete mortar bed (i think?). The bed is about 1.5" thick and appears to be mounted on top of metal chicken wire on a plywood subfloor (pics below). The consistency is almost like dirt, very crumbly in the areas where the tiles pulled up mortar.

Can someone please let me know the best way to go over this base? I don't think i'm going to be able to remove the thin set because too much of the base mortar comes up with it & it is very well bonded. Also given that i'm in a condo pounding out the existing bed and pouring a new one is going to be tough.

Thoughts on the best material to just go over this? Was thinking SLC but seems like i'll need a lot of it and i have quite a few craters to fill.

Thanks in advance!

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evan1968 04-02-2014 08:01 PM

Would you happen to be in Jersey ?

Kimbo 04-02-2014 08:02 PM

I'm in northern California. Thanks

John Bridge 04-02-2014 08:04 PM

Hi Steve. Welcome aboard. :)

You've just about said it yourself, but not quite. :) The entire mud bed needs to be removed, and a new mud bed needs to be installed. There is nothing you can put over that mess to make it work. Pull up the chicken wire, too. I looks like they didn't even use a moisture barrier under it (which is part of the reason it turned to mush).

jadnashua 04-02-2014 08:05 PM

Multiple family dwellings tend to have thick floors like that for two reasons: fire suppression and noise abatement.

IF it is quite soft, it may be a gypsum based product. To abide by the fire code, you probably need to either restore or rebuild that to a specific specification.

You probably should talk to whomever has a copy of the condo by-laws and get some guidance, and you may need to talk to the building inspector to ensure you don't do something that would create problems and maybe a big code violation.

It depends on what it is, and what they require, how best to restore it so you can put down new tile.

Chicken wire is not generally considered the proper material for reinforcement. You either use expanded metal lath or a welded metal mesh.

evan1968 04-02-2014 08:06 PM

Reason I asked is that looks like a typical Jersey Mud Job.
Someone might come along and say otherwise but im thinking that all has to come out before putting new tile in.
Dont think there is a fix for that.

John beat me to it!

reefone 04-02-2014 08:06 PM

craig op said the mud is 1.5" thick. so its not a jersey mud job.lol

looks like a typical mud job to me. to fix it id tear it out and start fresh.

evan1968 04-02-2014 08:11 PM

Yeah...what Jerry said.:D

Davy 04-02-2014 08:25 PM

Yep, just a dry pack mud job. They do make chicken war for plastering that is heavier gauge than regular chicken war. We use to use it on huge mud floors in Southern Cal. Can't say I've ever seen that heavy gauge war anywhere but in Cally. Like JB said, they forgot the tar paper.

Steve, dry pack is a poor mix of cement, just damp enough to hold it together. It doesn't get as hard as a concrete slab but it doesn't have to. Being a dry mix, it's much easier to level out that soupy concrete.

Kimbo 04-02-2014 08:28 PM

Thanks for the input all. So just curious what are the main risks if i tried to just fill a couple of the craters and thinly mud over the existing thin-set?

Floor is very level outside of the handful of craters created from pulling up the tile.

Lakee911 04-02-2014 08:49 PM

Why is no tar paper bad?

Kman 04-02-2014 09:43 PM

Is all the tile pulled up? If not, you're probably going to have a lot more craters to fill in. If the mud job is as dry as you say it is, it's probably not going to hold up to a lot of patching and leveling to suit you.

It's really not that big of a job to tear it out. Once you get a decent sized hole in it, the rest is a little easier. Without the tar paper in there for a moisture barrier, the subfloor most likely drew all the moisture out of the mud too quickly, causing it to be crumbly.

Kimbo 04-03-2014 01:36 PM

Haven't pulled up all the tile yet, but have a few new additions.

The floor layers appear to be as follows (top Down):

- Thin Set
- Mud Bed
- Chicken Wire
- Cork Board
- Tar Paper
- Unknown (haven't gotten to that layer yet).

Was able to see tar paper laid down inside one of the walls. Thought this would be a simple DIY project, but looks like i have to venture into the world of mud beds now...

Prior poster had mentioned that i should be concerned around building code/etc. If i keep the original height of the mud bed (1.5") -- any thoughts on how i identify the actual materials (so i maintain the original bed weight) - or would just using the lightest weight mud available (gypsum?) be my best bet? Plan to keep the cork board and everything else in place.

Richard Tunison 04-03-2014 01:45 PM

The material that was used is sand and cement in a ratio of 5 sand to 1 cement and mixed with a small amount of water so it just holds a ball in your fist. I'd use the same for your re-do.

Some nice guy wrote a good article on just how to make it.


jadnashua 04-03-2014 03:45 PM

A thick layer of cement (or gypsum) is both a good sound attenuator (be a nice neighbor, and hope the one above you is!) and will slow down a fire (may be required by your local fire code), so it could have been installed that way for one or both reasons. And, it is a good way to achieve a nice, level floor (doesn't mean they did, just that it is one other reason why they install that type of thing).

No biggie, normally, if you replicate it, might be if you chose some other method. Many condominiums have by-laws that dictate what you can do to the structural and neighbor impacting aspects of your unit, so it is important to understand those rules, or you could be fined, and the tearout/fix could be quite costly. At least that's the way it is in my condo.

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