We have a senior living housing project, 3 stories, concrete plank floor. After the stud walls are installed, a gyp / concrete floor underlayment will be installed. We specified a 4000 psi product. Owner wants to entertain cost savings options and they are interested in looking at 3000 psi options. It’s been a while since I have done this type of overlay and feel like this is not a good idea, but need technical reasons why.
4k products are kinda rare. They are usually in the 2-3k range. I have specified and installed this one on many Multi-family and office building floors, with no problems: Hacker Industries Firm-Fill 3310
I have limited recent experience with this type of underlayment as well but in my experience this was typically a 3,000 psi type product in our area.
If the facility’s operation requires rolling medical equipment (with those itsy bitsy wheels and heavy load) along the floor, I would insist on cement type with high psi. The lower strength products (usually gypsum) can rut from the concentrated rolling loads.
One hospital that I trouble-shooted had this problem; the solution was to remove all the sheet flooring and replace the underlayment.
For predominantly residential loading, the lower psi should be OK.