Underlay - Sub floor chip board except around fire place

[Courtyboy]

OK I'm on to my third room - the biggy. Laying solid oak T&G.

I have been using standard foam underlay as recomended by 'Wood You Like'. However, pulled up carpet in the lounge and around the fire place is a foot of concrete (rest of room is chip board like the other rooms).

Do I just stick foam on the bit of concrete? Or put some sealant on the concrete then the foam? Or a different underlay on just that bit?

As always, all suggestions much appreciated.

 

[WoodYouLike]

The concrete area is too small to have any major influence on the rest of the floor. Presumable it has been added there when the (new) fireplace has been installed and is just a thin layer - at least not going all the way down to the 'ground'?
You can use the same underlayment as in the rest of the room

 

[Courtyboy]

The concrete area is too small to have any major influence on the rest of the floor. Presumable it has been added there when the (new) fireplace has been installed and is just a thin layer - at least not going all the way down to the 'ground'?
You can use the same underlayment as in the rest of the room

No I think it was built like that. I assume to give some distance between the fires heat and the chipboard. No idea how far it goes down.

Do you think it would be sensible to paint it with some kind of damp sealant before hand? Or just don't worry about it.

 

[WoodYouLike]

You could do that - moist resistant paint, as long as you make sure it is dried sufficient before you put the underlayment over it.
What's underneath the chipboard?

 

[Courtyboy]

I'm not sure to be honest. Don't know how to get it up. No sign of screw, etc.