How performs Fibrerock compared to Gypsum FC layer.

5/8" Fibrerock is, I beleive heavier than 5/8" Gypsum FC pannels. Should it surpass Gypsum in STC performance? Thanks for your replies.

Sure, mass is mass - the more the better, as long as it's sealed hermetically. Each doubling of mass nets around 6 dB TL, so it wouldn't be a HUGE difference... Steve

Thanks for the answer. I've read on the site that you can get up to 8'X24' (yes 24 feet long) in ONE piece :shock: (that can help for potential leaks!) So this is should be quite heavy to carry. It needs a quite large door to deliver onsite. So the mass difference between Gypsum and Fiberock shouldn't worth it? I know that when you cut a Gypsum board you don't make big dust compared to Fiberock. The last one needs to be sawed so it spreads much more dust particles!

The mess and difficulty of cutting accurately might be a good reason to stay with gypsum... Steve