We have a new house with a 6-person, rectangular, 1000-liter hot tub installed on the terrace roof. Quite a bit of noise is transmitted into the house whenever it is running.

The roof structure was planned with the hot tub in mind and passed all inspections, so I am confident it is strong enough. The hot tub is currently installed on top of the membrane which is directly on the roof deck. Because of some issues with the roof and the way the hot tub is installed, we are going to be removing the membrane under the hot tub, creating a platform to raise the hot tub, and putting in place a new membrane over the platform, then a 1/2" thick rubber pad, and then the hot tub.

Can you make any suggestions on how to build the platform so as to minimize the noise transmitted into the house? (The manufacturer was sympathetic but of limited help.)

Thanks,