On Thu, 03 Sep 2015 12:57:28 -0400, John H.
wrote:


There is a big difference between a 'combat' engineer and a 'construction' engineer!
I read 'base floor' as 'basement floor'. Keep in mind that I'm getting pretty old.

Above the joists is plywood. I don't know if any 'backerboard' was used between the
plywood and the ceramic tile.


Typically you will actually have 2 layers of plywood or plywood and
backer if you are laying tile and these days they may also use a
membrane that will isolate the tile from the wood.
They even use a membrane on tile over concrete if the concrete is
green. That is mostly because they are not sure if the concrete is
going to crack. (mostly a function of the "build it fast" mentality)
I had terrazzo on my floor that was pristine 40 years later so we
trusted the floor.
You can also use "flex" mortar but it is about $15 a bag more than
regular thin set.
It is all I use because mortar is the cheapest thing you buy.
The only down side is it sticks too good. You are not getting that
tile back up if you chip one..