Hi Haggy & Mark
Thanks for getting back to me, if I go about 6 inches and a bit of mesh it looks as if it should be ok then.
I need to put some 3 x 2s down to do a new flloor and thought of keeping these flush with the new concrete slab and then cover the joists and slab in 18mm ply, then bolt the lathe through the floor and into the concrete. Hope do this in the next two weeks, I'll let you know how it turns out.
Rod