installing hardie backer board

[alamojo42]

hi my name is Don and i am trying to find out if i use modified thin set instead of unmodified thin set between the plywood subfloor and the backer board will i encounter any serious problems down the road

[CookeCarpentry]

You would want to use modified as the additives in it will allow it to cure and stick to the plywood, whereas unmodifed will not adhere to plywood.

[JazMan]

Hi Alamo,

Hardie tells you to use either modified or unmod to install the board, and modified only to install the tiles. You are not necessarily trying to bond the board to the subfloor. The thinset under is there to support the board so there is no movement. Problems down the road? Removing it in 20-30 years.

Jaz