Help/Advice re slate flooring over UFH

[Pigglet]

We are in the process of building a garden room extension that will be used as a dining room and kids play room, in reality it will probably be the most used room in the house when completed.
Floor construction is 125mm reinforced concrete slab with under floor heating in centre. The area of the floor is 35 square meters.
We have been looking at both natural slate and limestone flooring tiles, the one in particular my wife likes is this peacock slate with a riven finish : http://www.pricespaving.co.uk/product/peacock/

From a practical point of view the slate would have to be sealed due to the high wear area and issues with spillages etc. When talking to someone about it yesterday they suggested that sealing the tiles could cause all sorts of problems such as tiles lifting and trapped salts and condensation under the sealer making it look a mess. They said they would stay away from anything requiring a sealer on high traffic floors that are under floor heated.

Would you say they have a valid point or are given me bum info?
Also how long would you suggest leaving the concrete slab between pouring and tiling?
Any info and tips greatly appreciated

[wine~o]

Provided the slab has fully dried before tiling and sealing I can't see the problem

Normally you'd be looking at 1mm a day to fully dry, so at 125mm ...125 days (call it 3 months) with your underfloor heating on very low you might find that it dries quicker, but only if the room is getting plenty of ventilation.

HTH.

[Pigglet]

OK Thanks Wine-o