I am eco-renovating a 20s semi with concrete (I think) roof tiles. The roof has to come off for a loft conversion. The tiles are fine, but have been coated on the inside with PU foam for insulation. I'd like to reuse them, but have to get the foam off. Anyone know a good way of doing this? I've found a couple of solvents online but they seem to be aimed at cleaning equipment etc rather than working with this sort of bulk (hundreds of tiles coated to 50-100mm). Or there is sawing it off which looks likely to take ages. Any ideas gratefully received!