You can NOT use anything else. Vinyl does NOT like underpad. In fact it gets really wonky (it breaks) if it is used. There are a FEW manufacturers who use a SMALL amount of underlay (1.2mm cork is all that is allowed....or the floor moves too much and the click edges break). If you a product that has the integrated underlayment you are NOT allowed to use anything else.

If you purchase a vinyl plank floor that does NOT have the attached underlay, you *MIGHT be allowed to use 1.2mm mass-loaded vinyl (can be well over $1/sf). But this is RARE. Not all vinyl products are allowed underpadding. This is the MAIN difference between laminate and vinyl. Laminate is allowed 1" of cork underlay. Vinyl is NOT allowed underpad - at all.

You will have the concrete floor flattened (grind down the high spots and fill the low spots). You will install 6mil vapour barrier over the concrete before you install the floor.

Thanks for the response.
So I’m looking at a few products

1. 6mil poly...is the easy choice

Or

2. https://www.technoflexintl.com/products/consumers/technofloor-acoustic/

Or flooring store suggests this

3. http://floorsxtra.com/product/husssh-ii-premium-high-density-acoustic-pad/

Thoughts?

Here's what is allowed (listed from above):

#1 - 6mil polysheeting = YES...always (plus Red Duct Tape = moisture resistant)

#2 - NOT ALLOWED - it is UNDERPAD that is 2mm THICK! Wrong, wrong and more wrong!

#3 - NOT ALLOWED - it is UNDERPAD that is 1.5mm THICK! Wrong, wrong and again wrong!

Remember: your chosen floor HAS UNDERPAD. That means it is NOT ALLOWED to have more added. That's it. That's the end of the line. Nothing else is allowed.

Your statement, " Manufacturer says you don’t need an underlayment because it has cork backing " is what counts.

It's the FLOORING manufacturer who lets you use 'padding' or not. The cork-attachment PREVENTS ANYTHING ELSE. The 'don't need' is in fact a technical statement that reads IS NOT ALLOWED!

If you need acoustic insulation then PLEASE work with 12mm laminate (NO BACKING) and add in 12mm cork underlayment. Vinyl is SUPER DUPER HARD to get 'under pad' underneath. It is SOOOO hard (how hard is it SJ?) it is considered 'impossible'. That's why vinyl is not allowed in condos....you cannot get enough acoustic insulation underneath it to reach the HOA requirements.

Thanks again for your patience with me. I’m spending money on the flooring and just want to make sure i get the best bang for my buck. Thanks!

Not a problem. The best place to spend money = subfloor prep. A nicely prepared basement slab will cost $2/sf to get flat. If it is a nasty looking slab then the price can climb to $4/sf. Nope. Not kidding.

There is no way around the subfloor prep. Especially with vinyl. Any wavy/wonkiness in the subfloor is going to cause issues with how the floor 'feels' underfoot. The BIGGEST upset is the bounce or movement of an LVP. That issue is 100% due to improper subfloor preparation spending. If you spent $1/sf, then you can be 99% sure you will have some problem with how the floor 'feels' when you walk on it.

The second biggest complaint about LVP = 'squeaking, crackling, popping' noises. These are often seen with a floor that has an incorporated underlayment. Not always....but very often.