Appropriate subfloor over floorboards/tile

Hi all, im looking to fit (DIY) solid wood parquet over 2 rooms and had questions about subfloor preparation.

One room has floorboards that are in quite good condition except for a couple of spots. And i’ve just disovered the other room has quarry tile (i think? picture attached).

My plan was to put down a 6mm ply subfloor in both rooms, screw it down in one but wondered if there was a particularly adhesive that people would recommend for the other room? and if this 6mm ply is an appropriate choice for both rooms, and whether I need to do any additional steps to board over the tile

Also I initially planned to run this through both rooms without any threshold but im curious if it would be better practice to have a threshold due to the different types of flooring underneath the ply?

Thanks.

 

I don’t think solid oak over that is a good idea. How old is the house? Had you had any moisture readings? You should check the tiles and floor boards for moisture

 

The house is 60's, i've got moisture reading on the floorboards between 6-9%

 

Floor boards are spot on then. What’s under the tiles? They look damp

 

To be honest im not really sure, cant see an obvious spot to check, attached a couple of pictures now that most of it is up, theres wood at the threshold between the hall/bathroom thats giving me a reading of 10%, might get a better look when the other bars are taken up.

 

Needed ardex NA and DPM1c but wouldn’t be bonding any wood.