Hi all.

At the stage of laying a stone flag floor on insulated concrete subfloor with UFH under 65mm screed. Looking at 30mm sandstone flags, 600x600mm or similar. Was planning to lay them on a lime mortar but was blinded by science at tile stockists. He suggests planing surface of screed to dead flush, turning on UFH for a few weeks to open up any cracks; filling them with a filler compound, sealing the screed, laying a 'flexible adhesive'; then stone; then seal.

Anyone any experience of this and any pointers? Would prefer a simpler route if possible.

Thanks.

Hi Roger,

Your local tile stockist is talking crap. no experience. I have installed 2 UFH systems using a lime screed encapsulating UFH unbonded on 60mm 300Kpa extruded polystryene insulation on a concrete oversite. Random thickness York stone flags were then bedded on top of screed with lime mortar. The first building was a 12th century manor house in Alderly Edge and the second an adjacent barn. Both projects went like a dream with no problems.

I have photos of the barn which I can email you if you wish. You can contact me at: warmwater@blueyonder.co.uk I will talk you through the project.

Regards Cliff.

Roger,

Do not forget perimeter expansion detail and expansion joints in screed. Doorways can crack along with any projections into room like a fireplace. Any screed will crack for lots of different reasons you just have to try and elliminate them.

Regards Cliff

It sounds to me that the perimeter insulation being talked about is way too thin and may be being sued not as insulation but as a movement control joint.