Bathroom floor

[mauler]

I have a question about my bathroom floor. I am getting ready to lay tile. My subfloor is wood with 2x12s on 16oc. I have 1/4 inch Hardy board. I am going to put thinset under the board and fasten it to the floor with Hardy board screws. I was told to use a 1/4 notch trowel to apply the thinset. How thick do I need to apply the thinset and how long after I fasten the boards do I need to wait to lay the tile?

[Brad Denny]

Hi M,
Do you have a first name for us to use? (check link below my name)
The thickness of thinset under the board should be the thickness of that notch trowel when you put it on. Flat trowel the mortar with the un-notched side first, then hold the trowel at least 45* to get a nice set of ridges to set the board in. Hardi is notorious for being thirsty, so you might wanna sponge it down with water before you set it to keep the thinset from losing its bonding strength.
What type of subfloor do you have?? (important question)

[mauler]

It is either 5/8 or 3/4 plywood.