The Natural Philosopher wrote:

Why stik chipboard over it?

Because it's upstairs in our upsideown house, so, only acting to help
heat transfer from UFH pipes laid between joists (supported by 9mm
ply/batens/45mm cellotex)

http://gymratz.co.uk/pete/floor.JPG
(Rockwool for sound insulation purposes)

I have dilemma'd(?) over flooring surface, and real wood or engineered
(preferred on UFH) boards have been toyd with, but as we prolly want
tiles in the kitchen and bathroom area we need a flooring to put them
on, hence 18mm moisture resistant chipboard throughout. Then, probabally
a 7mm hardwood faced top layer.

Though the final surface still is not decided on, but a chipboard deck
on the joists is currently the favoured route as it can be laid quickly,
and would be liveable with no other surface down for wall/ceiling
decorating and kitchen fitting purposes etc.

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