What thinset between plywood and Hardie board?
Hey everyone, this is my first post here, hello.
I am remodeling a master bath and have some questions regarding thinsets. My house was built in 1969, the construction consists of 2x8 joists(unknown species) spaced 16" OC with a 10' span. The subfloor consistes of a layer of 5/8" plywood and then a 3/4" layer of ply on top of that. I will be installing 1/4 Hardie board as an underlayment for ceramic tile. The total area to be tiled, minus the walk in shower, is right about 60 SQFT.
My main question, really I have 2, is what thinset should I use between the plywood and the Hardie? I have read suggestions of both modified and/or unmodified. I also understand that the thinset in this appplication isn't used to adhere the Hardie to the plywood, rather just to fill in any dips in the subfloor to fully support the Hardie and the in turn the tile. So, if I bought a modified thinset that says not to use over plywood, will this be a problem? Does that mean I shouldn't use it at all over plywood, or only if I'm attempting to install tile directly to the plywood. Should I take this back and get a different product. I'm sort of limited to Lowes and HD products. Lowes here carries Mapei products, and I don't remember what HD here sells. The thinset I currently have, but haven't used, is the Mapei Ceramic Tile Mortar. It is a modified thinset, but it does specify that it isn't for use over plywood.
Is there a good product available at either Lowes or HD that will do well to set both the plywood to Hardie and my tile to the Hardie, I guess that would be ideal.
Also, what trowel is best used for setting 3x5 Hardie boards to plywood?
Thanks in advance for any input.