Originally Posted by TMAllison

I'd go with a topping from someone like Ardex or equalivent. They have products that aren't self leveling too and that are designed for 1" type fills.

Another option would be to speak to your local concrete plant and see what mix designs they have for a 1" topping pour. Bonded, it should work fine if the original is dimensionally stable and free of contaminants. I once did a 3/4" concrete topping over visqueen, over slabs on as well as above grade which was used as a temporary pedestrian traffic surface until I could get some special order slate hand sorted in India to do the job to the silly owners satisfaction. Even though it was an unreinforced, floating topping it was still in reasonable shape 9 mos later when we demo'd it and tiled it.

Originally Posted by Skid Row Joe

Isn't imported slate fun? I could tell you two nightmare incidences of how silly, well-heeled customers culled tubs and containers of what they deemed "defective slate," then called for replacement slate for the culled product......oh yeah, "and arrange for transportation back to your yard for the defective slate,"........geesh!

Originally Posted by Chas H

I have no way to reduce/scan the plans for a friends building completed about 20 years ago using a raft foundation.
I doubt you have inspected the house being discussed so you have as much idea as me how it was constructed.