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do you recommend 1/4 or 1/2 inch hardibacker for porch floor?

Posted by springplanter (My Page) on
Sun, Nov 10, 13 at 13:29

We will be installing either ceramic tile or stone over the screened porch floor underlay hardibacker. This is a 14 x 14 room over an insulated basement space.

I have seen both 1/4 and 1/2 in hardibacker recommended for floors Which is best for this space?

And in this case, should the hardibacker be installed with thin-set underneath?

Thanks for your replies


Follow-Up Postings:

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RE: do you recommend 1/4 or 1/2 inch hardibacker for porch floor?

"And in this case, should the hardibacker be installed with thin-set underneath?"

In EVERY CASE hardibacker must be installed with thinset underneath. Any contractor who omits this step is a HACK!

Sorry to shout, but this is one thing that really aggravates me, contractors who don't read the installation manual, or refuse to follow it because they know other guys who cut corners and they have been getting away with it.

And to answer the first question, 1/4" is for floors. The reason is you don't want to overload the floor. Cement board underlayment does not add any stiffness to the subfloor. It actually causes a bit of sag, due to the additional weight. If your subfloor is too thin, or has too much deflection, the joists need to be strengthened, or the subfloor must be replaced with thicker material.

1/2" cement board is for walls, designed to fasten directly to the studs. It behaves differently in a vertical position, sag is not a factor.

And for a semi-exterior space that will be getting wet sometimes, I would recommend installing a schluter membrane over the cement board. This will prevent water from seeping into the floor, and keep the tiles from popping loose.


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