Generally, with proper joist framing you want a minimum of 1-1/8" thickness of plywood under the tile. It's usually accomplished with 3/4" subfloor and 1/2" underlayment.

If he used SLC over an inadequate subfloor, then vertical movement/flex in the floor could cause the SLC to fracture. That can give the crunchy sound.

It can also happen if SLC primer wasn't used to bond the SLC to the plywood, the SLC has a higher chance of losing it's bond. OR if the SLC was poured directly over OSB instead of plywood. OSB is not a suitable base for SLC.

With the tiles being bonded to the SLC, if the SLC loses its bond with the subfloor, then the tiles has essentially lost their bond with the subfloor too.

SLC is a fine tile base if the subfloor/underlayment combo is adequate.

The only sure way to reset the bond of the individual tiles is to grind out the grout, pop out the loose tiles, and individually reset them with highly modified thinset. While that doesn't address any potential overall deficiencies with the floor, it'll take care of the individual tiles.

Get some specifics on the floor assembly from your tiler before you proceed. Depending on his methods of construction, it might fine to spot repair the floor, or it might be best in the long term to demo and redo the entire floor.

Thank you Mongoct. I really wish I was paying more attention to how he poured the SLC. I do not recall him painting out the plywood with any kind of primer before pouring it. If he did not use a primer, how do you assess whether or not the problem is the SLC? Would it be coming off from the plywood and would you see that once you removed some tiles?

Also, I went to Lowe's today and had a conversation with a salesperson who said the crunching might be caused if the contractor used a thin set that did not have a polymer component. Apparently the thin set with the polymer ensures that the bond holding the tile to the SLC flexes to accomodate any flexing in the subfloor below. I don't know if that's possibly the problem, that he used the wrong thin set and now that the weather is cold the flexion is causing the bonding material to crack and causing the grinding crunchy sound. Have you ever heard of this occuring before?

Ack! Gosh, next time I'll think long and hard before any home reno!!!!

Unmodified thinset (no latex modifier or "polymer component" added) still has a decent bond, and it's filly approved for your installation. Modified thinsets do have better bond strength.

Were he to tile directly to the plywood, then a highly modified thinset would be needed.

But still the primary concern is the flex of the floor. If the SLC and tile was put right over an inadequate tiling base, that in and of itself is your cause. Everything else is a result.

Could it be the thinset? It could. But the thinset bond, even unmodified, can still be quite strong. But usually with "crunchy floors" it's an SLC issue. The SLC has fractured, or the SLC has lost its bond with the underlayment.

Thinset bonds usually fail due to the thinset being allowed to skin over before the tile is set, or thinsetting over a dirty floor. "Dirty" usually isn't an issue with tiling over newly poured SLC, but it can be an issue with pouring SLC over a dirty or dusty underlayment/subfloor.

Ring your tile guy up and have him come out for a look.

Best, Mongo

"Generally, with proper joist framing you want a minimum of 1-1/8" thickness of plywood under the tile. It's usually accomplished with 3/4" subfloor and 1/2" underlayment. "

If by "underlayment" you mean a cement board product, you have a problem.

Cement board provides no stiffness improvement, unlike another layer of plywood.

The WOOD needs to be about 1 inch thick (and that is still only for smaller tiles).
Larger tiles require even stiffer support (similar to natural stone).

Hi brickeyee, there is definitely only 1 layer of plywood beneath my tile. One layer of plywood with SLC poured over that and tile over that. No second layer of plywood or cement board product.

So...this is a bathroom and the cabinets are set w/granite countertops. The tiles were set BEFORE the cabinets went down. Is there a way to cut tile out from around the cabinet base so that we can start from scratch? There is no way to cut the cabinets.

Also, if the SLC is failing, can you tell that from how it looks? Just thinking if the bond between the plywood and the SLC is the problem you might not see that without scraping up SLC...

"If by "underlayment" you mean a cement board product, you have a problem.

I made no reference to cement board in my post. I mean exactly what I wrote, which was "...you want a minimum of 1-1/8" thickness of plywood under the tile."

"If by "underlayment" you mean a cement board product, you have a problem.

I made no reference to cement board in my post. I mean exactly what I wrote, which was "...you want a minimum of 1-1/8" thickness of plywood under the tile."

"It's usually accomplished with 3/4" subfloor and 1/2" underlayment."

So what "underlayment" are you calling out?

If you meant plywood why didn't you say plywood?

Snooze alert, long post:

Judith, a follow-up for you. You wrote: "Hi brickeyee, there is definitely only 1 layer of plywood beneath my tile. One layer of plywood with SLC poured over that and tile over that. No second layer of plywood or cement board product."

A little background for you. There are two areas of delflection that need to be considered when tiling; the deflection of the joists along their length, and the deflection of the plywood between the typical 16" on-center spacing between adjacent joists.

The joist deflection is usually not a problem for ceramic tile 12" square and smaller. It certainly can be, but other things are usually at fault.

A single layer of plywood, however, does not have enough flexural resistance across the 16" joist spacing to properly support tile. That's where the two layers of plywood come in, it's typically 3/4" subfloor covered with 1/2" underlayment, with the panel seams offset from one layer to the next.

The SLC could have then been poured over the plywood underlayment, and then tile over the SLC.

As brickeye mentioned in his previous post, cement board over a singe layer of plywood is no good either. Cement board is not structural. It simply acts as a transitional material when going from plywood to tile. But it does not add strength to the floor like a second layer of plywood.

What your guy did, which was SLC over a single layer of typical plywood subfloor, and tile over the SLC, does not meet and industry standards. It's inadequate.

Any flexing in the subfloor may cause the SLC to fracture. Any further flexing, when you walk across the floor for example, will cause the fractured SLC edges to rub against one another, causing the crunchy sound you hear.

As you've discovered, the grout and tile can look perfect, the floor can feel perfect underfoot, but the installation is nonetheless broken.

To tile over a single layer of plywood, like 3/4" plywood subfloor, you'd first need a membrane like Ditra. Ditra is an uncoupling membrane, meaning that it acts as a go-between when transitioning from the plywood subfloor underneath the Ditra to the tile on top of the Ditra.

Ditra is about 1/8" thick and it has a 3-D waffle-type pattern on it, you can sort of think of it as a shock absorber. The 3-D waffle structure absorbs minor flexing from the subfloor below the Ditra, and by absorbing those flexural stresses, it does not pass them on to the tile and grout above.

For your floor, assuming your joists are properly sized, I'd want to remove the tile and the SLC. The tile could be cut flush at the base of the vanity, the vanity would not necessarily have to be pulled.

Since your subfloor will be somewhat ratty after the demolition, I'd then install new plywood underlayment over the subfloor. Then either cement board or Ditra over the underlayment. Most likely Ditra to minimize elevation gain. Then tile.

Adding 3/8" plywood underlayment over your subfloor to provide a clean working surface, followed by Ditra over the underlayment, will raise your floor height by about 1/2" less the thickness of the SLC that was removed. So if you had 1/4" of SLC over the original subfloor, your new tile will be about 1/4" higher than your existing tile.

3/8" ply for underlayent is about the thinnest I like to use, I'm not a big fan of 1/4" due to it being too flimsy. But that's personal opinion.

If you can cope with that added height at the door threshold, as well as coping with your vanity countertop essentially being lowered a bit (because the floor surrounding the vanity was raised), terrific.

That's just one option and my personal opinion.

Hi Mongoct. I just checked in to the site and found your posting. Thank you for that incredibly intelligent and detailed answer.

I am a little worried about what the contractor is going to do about this, he's coming in January to look it all over. By the way, if we can get any of the already installed tiles up off the floor unbroken and can clean the back sides of them really well, do you think we can reuse them? Is it better to just buy all new tiles? I can still get the tiles, no problem. Also, is it the contractor's responsibility to pay for all the additional materials needed to correct this problem or is it mine? I've already paid him for the entire bathroom remodeling job (about $8k!). There's no $$$ held back at this point.

Oh, regarding height changes -- well, not a problem. I installed regular kitchen cabinet height vanities so the additional floor height will be fine.

Thank you so much, happy holidays to you (and everyone else reading this).

Well, the work is recent, it's not like you're coming back at the guy years after the work was done.

I would recommend putting a camcorder on the floor and walking across it to record the crunch. These things can sometimes be seasonal, who knows. But that way you'll have the crunch documented and date stamped.

Your guy simply violated industry standard. Was it ignorance? Apathy? Who knows. But your floor is broken.

I have had to reuse tile a couple of times, it was when using old discontinued tile that had value. I'd cut them out of the floor, then use a grinder followed by a belt sander with a 36-grit belt to waste away as much mortar/thinset off the backs as possible. Reclaiming them was a time eater, it's up to you and your tile guy to come up with a solution of labor versus time in reclaiming the old tile versus buying new.

If he simply is a nice guy who inadvertently did poor work, I'd say that in fairness your maximum responsibility would be for the materials that he left out the first time, mainly the cost of the extra plywood underlayment. It's not your responsibility to pay for materials that you paid for him to provide.

If you want to get nit-picky, in some cases, if YOU provided materials, for example you bought the tile on your own and handed it off to him, then there can be pushback from him over that. That's sort of delving into the general contractor versus subcontractor versus who supplied the materials argument.

Typically when things like this need to be redone, each party brings to the table the second time what they brought to the table the first time, if that makes sense. Is that how it will work out? I really can't say. There is often push back from subcontractors in these cases.

Without a doubt it's his ethical responsibility (my opinion) to make it right, and ethically I'd expect him to do everything at no cost to you, again with the exception of you paying for the left out underlayment. And that's with you being generous, as you'll suffer the loss of your bathroom for a week or two whole the repairs are made.

In the end, there's always small claims court. If he indeed did poor work and if he indeed refuses to make the floor right at his expense, then you can get estimates from others for the cost of repairs, then take him to small claims court.

But you do have to give him the opportunity to make repairs on his own prior to taking him to court. Unless he's a complete knucklehead, dangerous, threatens you, or the relationship becomes adversarial, etc, to the point where you truly don't want this guy in your house.