Hi
I am adding a shower to a laundry/bathroom (9'x10')and have to break the floor for the drain... The room is at ground level and the concrete floor attached to the foundation on one side, cinder block walls on 2 others and in the middle of winter it is like walking on an ice cube. (let alone sitting on the toilet - in Ottawa, Ontario) Most of the drain lines for the rest of the house come down the walls and go under this slab and then down under the basement of our 1960's side split... (copper with Cast iron main drains.)

The questions:
I want to replace the current concrete slab and make it much warmer and am not sure with what. Foam board under new concrete is the most obvious approach? One thought is not to replace with concrete. Would high compression foam board with plywood over top be strong enough to support/distribute the load over time - would have to look at how to support the walls (attach to concrete/cinder block...?) Not sure about the fire protection layer for the foam board? also for any solution involving insulating do I have to be concerned with the drain lines under the "new" floor and freezing. (Currently "warming" that space with the uninsulated concrete floor.) I would prefer to stay away from radian heating for this space but it is not ruled out... would be the easiest though.
Hava every little flexibility with floor height changes, at one point was thinking of Dry Core floor on top of the current floor.

Thoughts, comments

Thanks

Mark

Hardwood flooring can be glued to concrete slab floors. That is what we have done to ours.
Also we once lived in a home that had the water pipes running along the side of the inside walls. they were covered with decorative metal vents. Looked quiet nice. Come in bronze, white, gold or can be painted you your choice.Also there were electric heaters running along the opposite wall.Maybe this might be your answer.

If you have the head room for drycor, you can install radiant heat on the floor between sleepers and then cover the floor with plywood and carpet or most any other types of flooring. Electical or hot water will work. You should expect to loose about 2 inches of height once done. Do not forget you do not have to do the entire floor with the radiant floor heat. only the areas in which you walk, Nothing under furniture or storage areas. Also many electrical radiant systems can be set into thinset and tiled over. Then area rugs for foot comfort can be placed down. You will loose little in head room and make the basement area much more healthy then by using carpet alone.

You can like you said put foam on the floor between sleepers and lay plywood over it. Be sure to place at least a 6 mill plastic barrier on the floor before laying the sleepers and foam. If water ever gets below you will rot the floor and create a mold issue which is very expensive to fix later on.