can you use compression joints on a hot water pipe within a floating floor?

Yes you can. Also can use push fit plastic joints ["Speedfit" or similar] Make sure the pipe ends are clean & joints are sound before covering. The whole pipe length will expand so allow for this. If both ends of pipe are totally rigidly fixed consider a flexi pipe in the length
Could be handy to be able to get at the joints at some future time

crumple
October 2009

Best use endless pipe or soldered fittings - but if any metalwork is to contact cement then it must be wrapped or run in a conduit. Why not use plastic barrier pipe?

John
October 2009