I need to know – why does every “authority” state that hardiebacker can not be set into liquid nails. It must be set into thinset. What’s the difference if the hardiebacker is being nailed to flat 3/4″ plywood? I’ve glued test pieces of hardiebacker to plywood with liquid nails and the layers of hardiebaker pull apart long before the plywood/hardiebacker joint. Any input would be appreciated.
Thanks
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The reason is that construction adhesives are squeezed out of a tube in random ribbons. This does not fully support the back of the board. Rather, it lifts the board up a bit, leaving unsupported hollow spots. If you installed tile over this, when someone walked on the floor the board would flex and you'd crack the grout joints and eventually pop the tile off.
Thinset is specified because when properly applied, provides continuous coverage supporting the back of the board.
The purpose of the thinset is not to hold it down.
It is to act as ground and give 100% solid connection to the sub-floor.
The reason I asked is because I know two ceramic tile installers - both of them use only nails to install hardiebacker. They say you don't need anything under it if it's nailed down good and they never have any problems. I thought liquid nails couldn't hurt.