I had thought about this. I know with indoor carpet, you lay the particle foam stuff underneath the carpet.
I wasn’t sure on what they do with outdoor carpet since you don’t want it to be “fluffy”, especially for a gym. Can I lay it down right over the concreate? I am concerned with heating and cooling of the garage. Is the floor a concern?
You can buy outdoor carpet without the padding which is what I think you are describing. You would not want to use padding. Institutional carpet works well, too.
We basically have two sections of the gym on top of 3/4 inch plywood with a real low, tight pile carpet.
The power rack, plus another sheet in front of it to accomodate a bench in the rack, stiff legs, RDL’s etc. off the pins, and a place to set plates and dumbbells during sets. We also have a seperate platform for pulling.
Arguably, the rest of a home gym could be concrete. You really only need to protect your working surfaces.
I would state you need plywood b/t the iron and the concrete under all circumstances.
Even when we used to use 4x8 rubber mats, we put sheets of plywood under them.
The carpet is much easier to maintain. Just vacuum it periodically and rotate the carpet 180 degrees every now and then to help it last longer.
Good luck with your project.