Home>Discussions>BATHROOMS>NO thinset between Hardibacker and subfloor
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Mauiblue
NO thinset between Hardibacker and subfloor

My contractor told me that despite hardibacker installation requirements he did not need to put thinset between the subfloor and hardibacker as long as he nailed the hardibacker down well.

Should I have him take it up and put the thinset down? :confused:

dj1
Re: NO thinset between Hardibacker and subfloor

You contractor is correct, providing he placed a 6 mm moisture barrier between the two.

I'd use screws instead of nails and follow the screw schedule precisely.

You use thinset to set the porcelain tiles on the hardibackers.

Mauiblue
Re: NO thinset between Hardibacker and subfloor

No moisture barrier was used between the two.

He did not use a vapor barrier underneath the tub surround hardibacker he put up as well. The wall is interior with no insulation.

Thank you!

HoustonRemodeler
Re: NO thinset between Hardibacker and subfloor

I will politely disagree with my colleague. TCNA guide lines are very clear as well as manufacturer instructions. The board was installed incorrectly and should be removed.

The sheet vinyl or plastic underneath can do more damage than good.

Timothy Miller
Re: NO thinset between Hardibacker and subfloor

Howdy go to the John Hardi web page an look at the best practices ( more information the then instruction section my opinion0 an the instillation instruction pages- very informative.

dj1
Re: NO thinset between Hardibacker and subfloor
HoustonRemodeler wrote:

I will politely disagree with my colleague. TCNA guide lines are very clear as well as manufacturer instructions. The board was installed incorrectly and should be removed.

The sheet vinyl or plastic underneath can do more damage than good.

Thanks Houston for correcting me...I was thinkind a different scenario!

keith3267
Re: NO thinset between Hardibacker and subfloor

In a This Old House magazine issue a couple of years ago, the late Joe Ferrante recommended using construction adhesive instead of thinset under the cement backer board on the floors. I followed this advice and it has worked for me. I did not use a vapor barrier on the floor except in the shower pan, but I did use tar paper behind the hardi board on the walls. BTW, I did not use the hardi board brand of cement backer board on the floors but I did on the walls.

HoustonRemodeler
Re: NO thinset between Hardibacker and subfloor

When used on the walls sheet plastic or tap paper can be used as a moisture barrier behind ceement board. It should be overlapping the tub flange. The ceement board should almost set on the top of the tub flange, firmly against the studs and not sloped out at the bottom from overlapping the flange.

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