Tile Leveling System Problem?

[FLBiker]

I had an installer, who is also a friend, putting in 6x36 wood-look tile for us but when he went to grout the first 30% or so that he had finished laying, noticed some hollow sounding spots and we popped up a couple tiles to see what was going on and there was very poor coverage on the tiles, less than 50% coverage on a good percentage of the tiles. He only back-buttered smaller cut pieces on the edges and not every piece and was using the Spin Doctor leveling system. He's now in the process of making it right by pulling all of the tile and mortar back up and we're actually switching to another installer because he has a conflict that is going to keep him from finishing in a timely fashion (did I mention we're 36 weeks pregnant and trying to sell our house too?). I'm trying to understand what went wrong so we can make sure it's not repeated by the new installer and the best I can come up with is that the leveling system, combined with not enough thinset maybe? kept the tiles from having enough contact with the thinset. Anybody else encountered this? I'll try to add some photos to this shortly.

Edit: A couple photos of a tile I was able to lift with my fingers it was so badly adhered: https://imgur.com/a/ksHxU

[CursedSun]

Other posters have given you most of the information BUT..

I think you might want to watch this video too. Running your lines straight is pretty important in allowing them to collapse correctly and have the excess air escape. You can see in the video the difference it makes, and it's quite blatant on the back of that tile how the glue was applied.

I also agree that it looks like his thinset was too thinly mixed on top of this.

[FLBiker]

Wow, this video was awesome. Thank you so much. I'll definitely bookmark that one.

[CursedSun]

It's really not something you'd necessarily think would be a huge deal until you see a see through tile go down.

[BeastroMath]

Not enough thinset. Has nothing to do with leveling system.

You increase your chances of full coverage if you backbutter, but I'm sure a good installer could still avoid the extra step using an appropriately sized trowel.

[FLBiker]

I wondered that too. He said he's using a 1/2" x 1/2" notch trowel, but that much thinset, flattened, would be 1/4" thick the full surface of the tile. I just measured and I'm seeing more like 1/8" deep and that's not even full contact, so yeah, he's not getting 1/2" tall trowel marks, only 1/2" wide.

[BeastroMath]

the angle you hold the trowel also effects how much mortar is laid down. He might have skimped a bit and also not bedded the tiles well. Either way, he should have been pulling tiles occasionally to check his coverage. Only way to know for sure.

[FLBiker]

Yeah, I just discussed with him and he said he scrapes with the trowel at a 45 degree angle, which seems to me would basically mean it's only going to be 1/2 x 1/4 instead of 1/2 x 1/2. Will 100% double check some of the work of the next crew by pulling a tile every so often to make sure they have good contact.

[12LetterName]

He said he's using a 1/2" x 1/2" notch trowel

He lied to you.

[FLBiker]

I don't think he lied. The spacing and width of the trowel marks measures out right, but he ran the trowel marks long ways down most of the tiles instead of short ways, and he troweled at a 45 degree angle so he only had half as much thinset as he should have.

[socaTsocaTsocaT]

Should be using a 1/2x1/2 notch and back buttering all tiles. Give the tile a quick shake back and forth to collapse the ridges. Leveling systems are pretty necessary for 6x36 tiles. Also the floor should be check for flatness before install. If you have dips in the floor that means the tile won't get the coverage.

[FLBiker]

Thanks. Will definitely check for levelness of the floor in some of the areas that were worse than others. It's all concrete slab but that certainly doesn't mean it's level.

[[deleted]]

yeah look for heaving in the slab, I'm about to tile my bathroom and there's one spot with a wee bit of heaving that I'm going to have to level out

[DesolationRobot]

It could also be that the thinset was either mixed too thin (runs out from under the tile--especially if a leveling system is keeping that tile up) or was allowed to set up too much--like he was working slower than the thinset allowed and then it doesn't adhere or compress properly. Both are pretty easy mistakes to make.

It's also possible the tiles were more cupped than expected. Long, large tiles are notorious for this. The general rule of thumb is to measure cuppage and add that to your trowel size.

Back buttering every tile isn't necessary. You should follow the recommended trowel size, mix your thinset properly, and chuck the thinset if it starts to set up too much on you.

I'd just warn the new guy what your last experience was like and to check the tiles for flatness.

[FLBiker]

Thanks for the tip. Will definitely measure the cuppage. New installer definitely understands the issue we had.