Okay, what's the real story here?

What do I need to put under the click-together planks or Allure or whatever desirable flooring other than carpet and padding, and not end up with frequent complaints from the tenant directly under that apartment telling me the upstairs tenant walks like an elephant?

Am I dreaming that such underlayment really exists?

What actually works well enough to abandon carpet in the apartments upstairs that have an apartment under them, OR tell me just give up any hope because I'll never find that dream product.

Thanks for reminding me why I never owned a 2 story rental.

A side x side duplex was bad enough.

I don't have any stacked units, and my one place with a "real" second story is still waiting for renovation, but I acquired an upstairs garage apartment that had been renovated by the former owner. The flooring was these thick, padded carpet squares that we eventually realized were the flooring you have for climbing walls. It was awesome stuff.

When we had a weird 1/2 with a finished attic, I was trying to hunt similar product down. I never was successful-- all the carpet squares were thin. Eventually, a flooring place clued me in, and I realized that what I was looking for was way out of our budget. So I ended up getting some of the thin carpet squares you use in offices.

Both have held up well. (We've had tenants in the garage apartment since 2014, plus whenever the original owner had done his renovation sometime between 2004-2008, and we've had tenants in the finished-attic-house since 2017.) But I like it because they have the benefit of being able to replace just-the-square if I do run into damage.

I don't think you can however... I have one client that has hardwood floors in the property (older, very beautiful property) and she requires that the tenants have area rugs put down (no, she does NOT provide them, it's a requirement).

It's really so the tenant doesn't just "move" furniture, etc and scratch and damage the floors but it also helps cut down on the noise. So you have these really nice floors and in areas where you are walking/sitting, etc (where the furniture is) your feet are on carpet.

Use LVP with an attached soundproofing underlayment.

The underlayment should have an IIC-STC rating of 70 or above to be virtually soundproof.

IITC-STC of 65 or above for superior sound proofing.

On the upper floors, use an additional separate multipurpose sound absorbing underlayment.

Make certain that the LVP with attached underlayment can also go over a separate underlayment without buckling or other problems. This will reduce impact noise.

IIRC, you can also use some additional protections, possibly specialty caulking where the walls joins the floors. This was to help with horizontal noise, not impact noise. I don't remember exactly what was recommended. So take this with a big tub of salt. Someone else may have better information.

IIRC, upgrade from a felt underlayment to a specialty sound proofing underlayment.

Like jonny says, also require the upstairs tenant have area rugs.

No carpet will result in tenant fistfights and frequent empty units. It takes maybe three hours to rip out and install new carpeting to get the unit back on the market.

Dino, if you carpet the upper level floor, you will get noise complaints from the lower level units. This issue won’t be solved by carpet, this is a screening issue.

You need considerate people living in these apartments.

BTW, if you install carpet, it will be slow to rent because people hate carpet. Your maintenance expenses will be higher too, your future turnover time will take longer.