For most vinyl flooring, what goes underneath is an underlayment or a prepared subfloor , depending on the vinyl type. In simple terms, it can be foam, cork, rubber, plywood, leveling compound, or a moisture barrier when needed, and some vinyl already has a built-in pad so nothing extra is required.

What usually goes under it

  • Foam underlayment: Adds cushioning and helps with sound.
  • Moisture barrier: Helps protect against water vapor, especially over concrete.
  • Plywood or leveling compound: Smooths uneven spots and creates a stable base.
  • Cork or rubber: Sometimes used for sound control and comfort.
  • Nothing extra: Some vinyl products, especially certain click-lock or pre-attached-pad types, are designed to go directly over a suitable subfloor.

What matters most

The right layer depends on the vinyl type, the condition of the subfloor, and whether the product already includes underlayment. A flat, clean, dry subfloor is the big priority, because vinyl shows bumps and low spots more easily than many other floors.

Quick rule of thumb

  • Glue-down vinyl: Usually goes on a properly prepared smooth subfloor.
  • Click-lock vinyl: May need underlayment if the product does not already include one.
  • Vinyl sheet flooring: Often needs a very smooth surface, sometimes plywood or underlayment prep.

If you want, I can also give you a simple “what goes under vinyl flooring by room” guide for kitchen, bathroom, and basement.