I think I have figured out my own issue but I wanted to ask the “Breaktime Guru’s”.

I’m not reinventing the wheel here. Typical home remodeling. I am in the kitchen fixing some damage to a floor. I have the new floor patched. The homeowner wants to lay tile in the kitchen over old vinyl. No big deal!

I know under typical conditions you would staple a layer of lauan (or other underlayment) overtop of the old floor if you couldn’t remove the vinyl (which is my issue) and start over with new vinyl. But since I am putting tile down, I was going to lay hardyboard (using liquid nails and screws) directly to the old floor. Simply using hardyboard in stead of lauan. Is this right?

And a p.s. question. We are debating the issue of countersinking the screw heads in hardyboard. My argument is that the the notches in trowel used for tile will compensate for some screw heads being slightly exposed. And I do NOT think you have to countersink. One of my buddies thinks that the screw head may cause the tile to eventually crack by being left exposed. What do you think?

David

Note: The attached photo really doesn’t show much. I took it as a reference a few weeks ago, not specifically for this discussion.