Sub floor

[aaront]

Have dug out the hearth in front of my (bricked in) fireplace as it was not needed and bridging the dpc.

I have dug down to bare mud (approx 8" below the floor joists). The rest of the sub floor is bone dry concrete. The mud is about 4" above this. I want to concrete over the hearth like the rest of the sub floor.

What materials do I need? I assume I dig down 6" below the concrete level, put in 3" of hardcore and then put 3" of concrete over that. Is that correct? Do I need to concrete it at all as it will not be loadbearing? What mix of concrete do i need? I am guessing 4:1 with sharp sand.

Thanks for any advice.

 

[masona]

Normally 3" to 4" backfill in 3/4" ballast/cement to the same level as the oversite then a course of brickwork with dpc with wallplate to pick up ex- floor joists.

I think I read your post right !