I've exposed our fireplace and removed the rubble from the rear hearth area, it's just earth and flint in there now and about 200mm deep. We plan to lay flooring so I need to fill the back hearth and then raise the whole lot to be level with the 15mm shuttering I have fixed. I was going to: 1. Whack down the rubble in the hole 2. Add layer of sand 3. DPM bottom and sides of hole, try and underlap the remaining bitumen DPC in the walls 4. Fill the back hole level with ballast/sand/cement mix 5. raise the remaining area to the 15mm shuttering with 3:1 sand cement mix + SBR My questions: - The whole area is very dry, no signs of moisture or damp, is DPM required? Doesn't appear to be one under the existing floor - Is 15mm too thin and will it probably crack? Should I maybe dig the remaining concrete substrate out a bit and use a floor levelling latex? - Is it overkill!? Once this is done I plan on using tile adhesive to lay the decorative granite hearth on top. It's a job for this weekend as the HETAS guy is coming end of next week to fit the log burner.