Underfloor heating under natural stone flags

[gavinharding]

I have just bought some old York stone flags of random sizes and thicknesses to lay as the floor to a conservatory. I have already laid an insulated concrete base with the intention of putting underfloor heating under the final floor covering. Normally I would bury the plastic underfloor pipes in 50mm of sharp sand and cement screed. Would this be a suitable material for bedding the flags, bearing in mind that they will need to be individually bedded? Or is there a better alternative?

[Tony McC]

No: what you have is fine. Embed the UFH pipes in the laying course, making sure you use a sharp/grit sand with no more than one-part-in-six cement. A lime-mortar as bedding is even better, but you need to check with your UFH supplier that there is no conflict between a lime mortar and the pipe material.