Advice on tiling old stone floor

[Icantsolder]

I have an old house (250 yrs old) which I am renovating. I have recently pulled up the lino to find a screed. The screed unfortunately was cracked and lifting (some of it was rather thin) and so I pulled this up too. Under this I have discovered the original flagstones. There was a bitumen type dpc present, which must have been doing something as the flags are damp in places.
I am not sure what to do now. I wanted to tile the kitchen (ceramic) and thought that a liquid dpc on the flags and then thick bed adhesive (flags a bit bumpy in places) may be best option. Also thought dpc, screed and tiles may work but am pushing it for depth in doorways (probably why old screed was so thin!).

Any advice would be gratefully received

 

[p.pittstop]

how are the flags fixed and at what depth is the substrate underneath them.

P.

 

[Icantsolder]

Joints between flags appears to be soil! or some very crumbly mortar. I think their shear weight is holding them in place.
Not sure what is underneath them but can get a blade between them to a depth of about 3-4 inches where it then hits something hard.

 

[keycare]

Why would you want to cover what could be 250yr old flagstones?

Are you rennovating or modernising?

Take up the flags, lay sub floor, DPM and screed, stick some electric UFH or even wet UFH and re-lay them. Old flags can be worth upto £60 sq.m. You must be mad to want to cover them with ceramic tiles!

Sorry for resurrecting an old post but this kind of thing makes me mad!

I'll get me coat