Why use thinset under backerboard

17 Thinset is going to create a solid surface under tile and prevent flexing that could lead to cracking. Using thinset between the backerboard and. My husband and I will be installing ceramic tile in our kitchen this weekend. We will be using thinset and nails to put our hardibacker board down. 21 You could put this over 1/4 subfloor if you are thinking about replacing tile down the road. Downside is it cost a bit more than cement board. I.