Is there a breathable underlay for wood flooring?

[middi]

The obvious thing to do, appears to me, is to repair your old flagstone floor.

It would definetely suit the building a lot better than it would suit your children.

The only really breatheable underlay you can use in your situation is called " fresh circulated air" especially over those flagstones.

 

[woodsmith]

If you still want to put down an oak floor and you are able to raise the floor by about 63mm you can lay 25mm insulation board (you could just use polystyrene but I use Extratherm boards) onto the floor. Lay a 1000 gauge damp proof layer over the insulation boards then lay moisture resistant chipboard flooring as a floating floor, gluing all the joints and leaving about a 15mm gap round the perimeter. You can then lay your oak floor onto the chipboard, I run a bead of flexible adhesive under one side of each board then secret nail through the tongue.

You need the damp proof layer to prevent any moisture coming up from the floor into the oak boards because timber expands across the grain as it absorbs moisture. It doesn't need a lot to make the floor expand enough to buckle.

I live in a Grade 2 listed barn conversion and I've done this to one room, the kitchen, and I'm just in the process of digging out the screed from the living room floor to do the same there.

It makes a very warm comfortable floor without doing any damage to the original flagged floor.