Tiling failure over wundafloor

Reading a previous thread I feel that there is hope for my situation. The names listed below are from contributors of the old thread, that is the only reason they are mentioned. Thank you.

@Localtiler, @3_fall , @jcrtiling - Guys I'm in desperate need for some PROFESSIONAL advice. I've saved for 10yrs to get my family home extended... I've had no house now for just under a year with 2 young children. This has literally broken me, so any advice would be massively appreciated.

I've had the wunda EPS 400 install to the whole of my downstairs as I have a 120 X 120 - 6mm ceramic tile laid. 1 month ago the floor protection was finally removed as my was kitchen installed. After waiting a whole year for this moment... I walked into a nightmare! A number of tiles have blow and all felt hollow. They have dot and dabbed my whole floor! After 4 week battling between my kitchen company (Tillers) builder (floor prep) I have finally got the kitchen company to agree to fix it... now I want it done properly!

Tilling: They used an adhesive to stick down a ditra matting directly on top of the boards before dotting and dabbing the tiles to get them level as the house is sloping by 30-40cm. Bal adhesive from Topps tiles. Very wrong!!!

Floor prep: The builder glued the boards directly onto the concrete floor (extension) and the existing wooden floor boards. No levelling at and the existing wooden floor area has movement when standing on it.

My question to you guys - The Kitchen company recommend removing the tiles and as much of the adhesive and then screeding it level - Reading this thread this doesn't seem right but will this work?
Or would you advice to remove the UFH and start again?

For both option do you have any experience with how you would do it?

@Localtiler, @3_fall , @jcrtiling
Do either of you do consultancy work and would be interested in helping me I'd be happy to compensate you for your time. I'm in south east London.

Your biggest problem is movement .some of your issues could be resolved without taking up the boards but you have to get rid of the floor bounce . Dotting and dabbing in any situation is wrong but with thin porcelain is absolute madness .
@3_fall is really the man for this as he has experience in rectifying faulty wundafloor installs .

Thanks @jcrtiling - Tiles are definitely coming up! Now its just a case of understanding if the UFH boards need to come up. It out by 30mm in areas so I don't think I have a choice. If I need to screed the floor to level it out any idea of the minimum depth the screed would need to be? and how I can achieve that same level over wooden floorboards?

You can get plenty of levellng compounds which go from 5 to 50 mm so that' no problem . Are you saying your timber is out of level or a different height to the cement screed.

Remove the heating boards make good floor level then install heating i would recommend warmup

Ok an update... the builder said the extension flooring area is chipboard and not concrete (least the whole downstairs is the same material)... and tested it with a laser level - The floor is only 15mm out over a 80m2 area (measuring from the surface of the ditra matting/ not the top of the dabs). The tiller used a large level to try and get the floor ask accurate as possible (not a laser level) hence them trying to build the levels using the dab method.
They are aiming to take all the tiles back up. Chip away the Dot and dabs and the use a 5-10mm self levelling screed on top of the ditra matting before tilling again.
I get this is not the correct way to do but can anyone advise if using Bal screed will stick on top of the ditra matting ok and then using bal flexible adhesive will work?
Some pictures... I hope this will help other out in the future...

What a mess!!! 10mm on top of ditra very risky! As you remove the dots i bet you will pull at the matting making it debond.. i wouldn't mess about i would rip the lot up!

As Andy says, not advised at all. I would start afresh

Just splitting hairs but that ditra matting looks like dural durabase

As above, you've paid for a proper job, that's what you should get. They're offering a solution which saves them money, but I don't think would last. Layering up leveler into old adhesive is not ideal and it will negate the properties of the durabase (cheap ditra alternative).
I can see the thinking behind the proposal but who's going to guarantee it?

It sure does look like Dural

Thank you all very much for your advice. Just call them, yes this is Dural. I've got a better chance of winning the lottery than getting them to agree to pulling this up and relay it!

Dural not a problem used loads of it without comebacks . It's just that if they quoted and charged schluter ditra price then fixed dural with different price point

If they won't do it, name and shame on as much social media as possible.
What's their reputation worth to them?

@impish I'm a digital marketer specialising in FB and insta... really don't want to go down that route...plus I'm better a promoting. Can anyone give me a rough costing for removing, relaying the boards (I will buy) and retiling. Its a open plan kitchen, dinner and front room. With a small downstairs toilet and utility. About 80m2.
Are any of you guys willing to travel to DA16?