Approximately how thick should adhesive be for floor tiles? Tiler only using 2mm thick

We needed a tiler to lay 46m2 of 800mm tiles to a concrete floor in our new shop. Everyone we tried was not available for a month+, but then through an acquaintance, my partner was told of someone who was available. I had my misgivings as I was wondering why he was available while everyone else seemed very busy, but due to time constraints we went with him. I wasn't any more reassured after meeting the tiler, even though he told us he that had 20 years experience, as I asked him if he was going to use a levelling system and he said he didn't need to. I told him I was worried about lipping and wanted a level floor so asked him to use one and I bought him a Mustang levelling system. He then asked us for £200 up front to buy tile adhesive, so we gave it to him.

He started the job last Thursday. I was there when he started as I wanted to see if he was going to back butter the tiles, something a tiler on here told me he should do. Needless to say, he was about to plonk a tile down without back buttering, so I told him I wanted him to back butter the tiles. He said that he would have to buy some more adhesive, but I persisted in saying that I wanted him to back butter.

Fast forward to today. We went to the shop to see how things were going as we knew half the floor had been done and that he would be starting again today. I'm a bit worried to say the least. Some of the tiles are lipping and the reason he gave was because the floor was not even and a little higher in places. I think it's more to do with the fact that he has only used about 2mm of adhesive, we can see this as the top of the tiles (which are 10mm deep) are only 12mm off the concrete. I would have thought it would be sensible to use a thicker bed of adhesive as this would give you room for manoever (up and down) if a floor was out a little, and using such a small amount to my mind, and should the need arise, gives him nowhere to go. I made a point of looking at the amount of adhesive he had used. When he started he brought in 10 x 20kg bags, he's only used three and has done 23m2. Because it is too late to change course, we have let him continue.

Now to my question, do you think I am worrying unnecessarily and the floor will be fine with 2mm of adhesive, or do you think I am right to be worried, in which case, what can be done?

Edit: I hope professional tilers on here don't think I'm being one of those people who is trying to tell a professional how to do their job, particularly as I'm a female with no experience of laying tiles, in fact my only 'experience' prior to starting this, was tiling videos with levelling systems, where they all seem to use much more adhesive.

Hi. There’s no way that 3 bags will do 23 mtrs. There is deffo something a miss fixing wise.
personally i would be popping a tile up and checking for coverage.

Dave said:

Hi. There’s no way that 3 bags will do 23 mtrs. There is deffo something a miss fixing wise.
personally i would be popping a tile up and checking for coverage.

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Hi thank you for your response. My partner said earlier he thinks we should let him do his job, (he is not fully well and cannot handle stress), so although that is something I would do in an ideal world, it's not something I can do right now. I suppose I am just looking for reassurance that the tiler knows what he is doing and everything will be okay.

Could 2mm be enough?

Frilly said:

Hi thank you for your response. My partner said earlier he thinks we should let him do his job, (he is not fully well and cannot handle stress), so although that is something I would do in an ideal world, it's not something I can do right now. I suppose I am just looking for reassurance that the tiler knows what he is doing and everything will be okay.

Could 2mm be enough?

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You wouldn’t even get 2mm bed depth with 3 bags. I seriously think you need to see what is going on under your tiles. Otherwise it could fail big style.

a sad state of affairs. You had a sensble thought at the beginning - Why is he available when the rest of the tiling world is stacked out - Your insticts were not reassured when you met him and yet you still used him.... why????

As David says deffinitely something wrong with the installation. 2mm is not sufficient adhesive. I wonder if its dot and dabbed which would use less adhesive if he used only small dots...

you are looking for reassurance that all will be well. Sadly it probably wont. You have a choice I guess, let him complete the job and hope for the best in the knowledge that it might fal and at that point you will want him to come back and fix it (he probably wont come back and fix it so the long and arduous and even more stressful route to litigation takes place), or you could stop him and insist that he fixes it now and does it properly although assuming your statement on his comments to be accurate he is probably not really capable of fixing it, or you could cut your losses, accept that you made a mistake in ever employing him and get someone else in to sort it out (either at your own cost or at the current "tilers" cost if you can get any money out of him.

I suppose it might be possible to reuse the tiles given the will have next to no adhesive on the backs....

on floors i tend to use a 12mm notched trowel then back butter tiles
if the floor is uneven which 9 out 10 are i would always self-level
especially using a large format tile

Could the 2mm bed your seeing be a high spot on the floor?

The fact he bought 10 bags at the start of the job says to me he planned to used approx 4.5m2 per bag which would be about right coverage wise. Could he of used more and purchased the additional adhesive already? As previously mentioned, something is not right with the adhesive usage ..

Any photos of the job ?

With a tile that size he should not be using any trowel smaller than 1/2x1/2" (12mm) and back buttering.
50 years tiling here.
I have seen many concrete floors and very seldom have any of then been flat!

Floor adhesive should be laid at a minimum of 5mm, once laid and bed this will be reduced, so 2mm is not unacceptable, and it might be in a high point, but tiles as mentioned should also be back buttered to meet the required 100% coverage, judging by adhesive used he is not doing the job correctly, as coverage nominally is 4-6sqm per bag.
Problem is what to do now!

To possibly put your mind at ease and answer some of your concerns.

There are numersous reasons why he could be available at short notice, it doesn't mean he doesn't know what he is doing.

The majority of tilers have been tiling very successfully for years without the need for levelling clips. Although they are good in certain situation.

Depending what adhesive he is using he could get upto 16/17 bags for £200, so I suspect he is using more than you think he is using.

As mentioned above the bit with what looks 2mm adhesive underneath could be a high spot on the floor, perhaps the floor may have needed levelling prior to tiling.

Having said all that don't be afraid to take one up to see what is going, better to do it now than have them fail when your shop is trading.

Hope it all works out.