Is this something a tiler would routinely suggest?

[Bluesheep8]

We have a large kitchen with huge old limestone effect tiles on the floor which must have been down for many years. We are replacing these with wood effect porcelain plank shaped tiles. I'm getting the distinct impression that the tiler is a bit concerned about taking the original ones up and about what's underneath (?) There has also suddenly been mention of tiling over the original ones (?) Not sure at all how this is an option as surely the difference in floor height from the hall to the kitchen would be a problem. What are your thoughts Please? Let me know if more detail is needed, or a pic of the current tiles....

Hi I have heard of tilers tiling over already existing tiles it's actually quite common practice (I was amazed). It's usually cheaper as it avoids any "hidden issues" as well - given what you have said I suspect this is why the tiler wants to do it. Re heights of the tiles I think you should ask him and see what his response is - some sand them to take the height down but that is messy.

Renovating my flat and just had to fire my builder - too lazy to do what I want and much refer to do his own thing.
We had problems with his tiling work in the bathroom and toilet. After that dismal job I would not allow him to touch the tiling in my kitchen.
Like you I am having porcelain plank tiles, similar to hardwood effect and multi tiles on the walls which would need special attention. Both tiles are expensive.
I would most definitely have those old tiles removed, you have no idea what is underneath them. If he does not want to do it, I would find someone else and stick to your guns.
I am having plywood over my floor boards, with the steam staggered, not lined up.
The plywood will enhance the strength of the floor, as with the tiles, you do not want the floor to start flexing, you need a solid floor.
My friend told me to also add ditra isolation membrane or equivalent before the tiles are laid along with modified thin-set.
Do some research on ditra isolation membrane along with modified thinset.

Thank you for such detailed responses and advice. I will look at that info and ring him to clarify.

Will it raise the kitchen floor up to a height where the entry door(s) will not open? What about thresholds? Will they be different heights and how does he intend to deal with this? An unsightly raised bar? What about any skirting? How will this be sorted out? Is there any and is it being taken off and replaced above the tiles? In my view its impossible to do what the tiler is suggesting and get a good finish.

Therefore, it is problematic whatever you decide to do. If you are gutting the kitchen I would get the tiles up and deal with the consequences. Uneven floor thresholds are a real pain.

is it a concrete floor under the tiles? If so it should be OK unless it is cracked, patched, sinking, or has been extended with one or more joins.

If it is a wooden floor, tiling is a great risk and likely to crack.

It might be that he can't be bothered to do the work of taking the old ones up. He should have allowed for it in the price. If not it will cost extra.

Thanks for replies, hard to tell what's beneath, but here's a pic of the current ones (they were here when we bought the house)