BTW will sandstone withstand saturation and repeated freezing? I
thought it was quite porous stuff, and one of the softest stones.


Not all sandstones are created equal, as I understand it. York stone has
been used for paving for hundreds of years and is still working OK.

I believe some stones are subject to delimination when subject to the
freeze-thaw cycle, but if you go to a reputable supplier you should get
something which will last OK.

Neil