OLD "concrete" basement "floor" need advice, please

[Yisroel]

Hello,

One 14x16 basement room in our 1898 home has an old hand-poured concrete floor which is THIN and verges on crumbly.

Hand-pours delaminate and veneer, crack and crumble. But, in the next room, one has been (mostly) holding up and serviceable for 20 years after we applied epoxy coating. This gives me hope that we can mostly depend on the floor being fully compressed, with out fear of settling.

I've family in the middle east, and they set tile in thinset right over compacted sand!

Anyhow...

We've chopped and swept to remove any scaling and and used bags of leveler to fill voids, and level it. Gradually made it look complete, solid and very flat.

Here we go:

Would uncoupling mat (like latacrete strata mat) thinset be the best bet to complete with 12x12 tile?

My "thinking" is that the mat would distribute the load and delink the tile from the old pourS below.

This, rather than asking of the tile to keep it all together...

If latacrete strata mat isn't the answer, what might be?

Thank you (all) in advance!

Eric

[cx]

Welcome, Eric.

A geographic location in your User Profile is always helpful.

The StrataMat is advertised as an uncoupling membrane and, as such, carries no industry standard at all. This particular mat advertises some crack isolation properties, but does not advertise meeting ANSI A118.12 standards as a crack isolation membrane.

As with all similar products it will carry a requirement such as:

Originally Posted by Laticrete

Note: Surfaces must be structurally sound, stable and
rigid enough to support ceramic/stone tile, thin brick
and similar finishes.

From your description, you may or may not be able to provide that.

Using such a product may help to some degree in your application. Operative word there is may. You'll want to go to the Laticrete website and download the TDS and read it carefully.

My opinion; worth price charged.

[Yisroel]

Burlington Vt

[Tool Guy - Kg]

Mmmmmmmm, Al’s French Frys in Burlington, VT!

For your floor, no matter who suggests what, I think it’s fair to say there’s a fair amount of speculation and we are going “off-grid” with possible solutions. With that, I’ll say that if your surface is well compacted, but mostly a bunch of “individual islands” of concrete all mashed together to make a single floor, then they will expand and contract individually. The “islands” of concrete will push up again and pull apart from each other during expansion and contraction that occurs through changes in temperature and moisture content. This movement might be the reason your epoxy coating is slightly failing. Is it more a failure through cracking? Or more of delaminating from the surface? The answer would point to your bigger weakness. Can you share a picture or two?

[Yisroel]

The cement is only a couple of inches over most of the floor.

Most common issue is that it sheds/veneers in spots, with traffic.


I've got a mid-grade lowes ceramic 12" tile that I bought out, on close out.


We've chopped out anything that looked ready to become free, filled the deepest voids with leveler. We will then apply concrete primer on the whole thing, then using leveler on most of it to make it as flat as possible. Currently it looks pretty close besides some fields that are lower.

I may be going overboard, but here's what I've committed to do:

I'm gonna spread straight thinset with 1/4" trowel and cover with
Laticrete Stratamat 1/8” Thickness mat (got a 323' roll for $250), and then thinset the tile on that. (Unless someone says to put more down with a different sized trowel.)

I was told not to use anything but straight thinset below the mat.

total material cost is about 500. for a 14x17 room

[cx]

Originally Posted by Eric

I was told not to use anything but straight thinset below the mat.

Don't know what that is, Eric. Thinset is a method of tile installation. Thinset mortar is a bonding material used in the thinset method. But I don't know what you might mean by "straight thinset."

[ss3964spd]

Since Eric is planning on Stratamat I'd venture a guess that "straight" thinset means unmodified thinset mortar.

[cx]

Thought that might be it, too, Dan, but Laticrete has no such requirement for StrataMat.

[Yisroel]

Yes, sorry, by “straight thinset” I meant unmodified.

And, yes, I’ve wondered if we could even use modified thinset
unlike with Ditra which evidently has no permeability.

Though a friend suggested that modified thinset would take forever to dry below a mat.

Again, we’re “thinking” that we’ll use a 1/4” notch trowel below the mat and also to set the tile.

TY, all!

[cx]

Eric, you really want to read and follow the manufacturer's installation instructions for this and all other products you intend to use for your project. It can really make a difference in the outcome. Your friend did not do that.

The size of the recommended notched trowel will also be found there. If your 1/4" trowel is a square notch, it is not the trowel recommended by the manufacturer.

My opinion; worth price charged.

[Yisroel]

Will do!

Thanks a ton.