Sub Floor for Vinyl
 

I'm planning to install vinyl in my laundry room because I have been advised not to use solid wood flooring. I want a level transition from vinyl to 3/4" wood flooring. So what product do I use to raise the subfloor up? I have cut plywood and there's a lot of voids. Thanks.

Use plywood and fill seams with a cementious based floor filler.

You need subfloor rated sanded plywood, that way the voids are filled in the core.