On the note of weight, a playing space of 8m*8m, with a roughly average depth of 8-10cm, used nearly 3.5 tonnes of dry sand! We were in the theatre for three weeks, and on the out, we found that the sand had removed all the varnish from the parquet floor in the auditorium. We were performing in the round, and the transfer simply from the cast and through airborne particles took the whole lot up.
On the subject of dust, PSMKay's suggestion sounds good. We just sprayed water from spray bottles before the cast were called, and again just before house opened.
The entire space was swept two or three times a day, carpet mats were placed at entrances (hoovered twice a day), and the sand was raked before the cast were called, and again at the half.
We also didn't find it necessary to put anything under the sand. The stage floor was painted, and the sand spread out on top.
The final suggestion I have it to ask the company (at all times, except dresses and performances) to bring in a second pair of shoes, and only use their costumes on the sand. Even with the regular raking and cleaning, I was regularly picking little stones and other bits from 'outside'.....
Any other questions, just ask!
HTH,
C