Installing new hearth over chipboard floating floor

[Buffon]

We recently had our chipboard floating floor replaced in the living room due to flood damage. When removing the damaged floors, the builders also had to remove our fireplace and marble hearth. Now that the floors are all back in, I'm ready to install a completely new fireplace.

I first need to install the hearth, but I'm slightly unsure about the correct approach. I obviously can't bed the new hearth directly on to the chipboard floor, so I've cut out and removed an area of chipboard beneath the location of the new hearth. This exposes the DPM which in turn lies on top of the polystyrene insulation.

Can anyone confirm the correct way to proceed from here? I'm thinking that I need to lift the exposed DPM, cut out and remove the polystyrene insulation, drop the DPM down onto the concrete beam-and-block subfloor, and then fill in with concrete up to the level of the top of the insulation?

If this is correct I can then place my dabs of plaster/cement onto the concrete when dry, and bed the new hearth down onto the dabs, leaving a small gap underneath the edges of the hearth to allow the chipboard flooring to continue to float. There would obviously then be no insulation directly below the hearth, and I'm not sure whether this would be correct.

I'd be really grateful for any suggestions or thoughts as to whether this might be the correct way to go.

Many thanks

[stoneyboy]

Buffon,
Yes your proposal is fine.
end

[Buffon]

Buffon,
Yes your proposal is fine.
end

Many thanks, Stoney.

It seemed like the obvious approach, but I'm grateful for the encouragement because I've drawn a blank trying to get confirmation of any building regulations requirements that might be applicable for this particular setting.

Regards,

Buffon

[welsh brickie]

hi buffon
Sounds good to me