Definitely read the installation manual. I'm more concerned about moisture and concrete prep than sanding.

Sooooo many complaints from homeowners who did NOT pay/insist on subfloor preparation!!!!! Karndean is thin and will TRANSFER any imperfection to your vinyl floor. You will see every pebble, every divot, every bit of sand left over.

The subfloors (both of them) MUST BE as smooth and flat as an ICE RINK!!! I would expect a preparation budget of $3-$5/sf....and then cost of floor + install.

The plywood needs preparation just as much as the concrete. And any vinyl floor can have issues with HOT temperatures like sitting in front of a window. Check your window UV ratings. They should be the "mid-range" option or HIGHER. That means a UV rating of 70% or higher "blocking". The entry level windows (Low-E) are around 50% UV blocking. You need to PAY for the UPGRADE to the windows to ensure the vinyl is happy.

And PLEASE look on houzz regarding Karndean PROBLEMS!!! There are DOZENS of threads with HUGE amounts of complaints with Karndean glue down products. HUGE complaints!

Buyer beware! (aka... Run away!).

Good luck....please think this through - again.

Agree, read the reviews. Here's one thread: https://www.houzz.com/discussions/do-your-karndean-floors-look-like-this-dsvw-vd~2378028?n=289

We were going to use Karndean until we read the reviews. They had a great reputation, but looks like recently there are many problems, some from install/prep but many with the flooring surfaces themselves, we didn't want to risk it.