I used 1/4" HardieBacker under a porcelain tile floor install and was extremely pleased with the rock-solid feel and soundproof-ness of the installation.

Now that I am preparing to install 3/4" solid plank flooring, nailed into 3/4" plywood subfloor, I was wondering why I never see HardieBacker listed as a suitable underlayment? Other than height considerations, this board would level the subfloor well and provide great sound isolation.

Are there potential problems with cleats holding?

Thanks for the replies!

You can use Hardi underneath a glue down or floating install if you so desire. It is not designed to function as a substrate for a mechanically fastened down floor. Staples will go thru it ease .... but there is not any holding power for the staples/cleats as plywood affords.

Thanks, Jerry. That's what I was thinking might be the problem.

Hi, First off I'm not a pro just a long time DIY. About 5 years ago, I put 1/4" hardie under my doug fir floors over the 3/4" ply sub. This is installed on joists over a basement. I have not had any issues since the install but I used nails that would just make it in to the joist as well.
Good luck

Thanks, Vic. I figured that HardieBacker would not present a problem if using only 1/4"; after all, I'm using 2" cleats.

However, I probably will not use HardieBacker simply because the installation instructions are specific about what and what cannot be used. HardieBacker is not disallowed specifically, but neither is it approved.

I don't want to take a chance with the warranty terms.

I still believe that this backing is phenomenal and great to work with.