First, 1 foot = 30.48cm (12 inches x 2.54 cm/inch=30.48 cm). So, 8,5 ft = 8.5 x 30.48cc=259.08 cm, 7.5 ft = 7.5 x 30.48=228.6cm and 9.5/12=0.791ft x 30.48 =24.11cm. So, in cc, 259.08 x 228.6 x 24.11 = 1,427,931.3 cc. Since 1 cc of water = 1 gram then we have 1,427,931`grams or 1427. 931 kg x 2.2 lbs/kg = 3141 pounds of water or 1.57 tonnes of water so with this size of waterbed if upstairs the house structure must be able to withstand this stress.