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Tile installer claims to have used hardiboard. Is it possible with this thickness?

2 points · submitted Mar 2025 by u/marktastic

Unfortunately there's no exposed edges. The tile itself (12" x 24") is a little over a quarter inch thick. But the total install thickness is about half an inch. It's my impression that the mortar thickness itself should end up being about a quarter inch, but they claim they used just a really thin layer. Last pic is a tile on top of quarter inch (exact) piece of trim.

I'm not asking if they should have used it or not, just that if they didn't, I don't want to be charged the extra $500 or so. Is it possible they did actually? Is quarter inch hardiboard actually quarter inch thick?

https://preview.redd.it/1p3nzqwu3ire1.jpg?width=4032&format=pjpg&auto=webp&s=d8f8e0c97d5d845467e321595e886e2c85210682

https://preview.redd.it/6kpvh0tu3ire1.jpg?width=4032&format=pjpg&auto=webp&s=8b7b82013c901d38f70f9ad4b93bf69faa388b0a

https://preview.redd.it/y17hmyou3ire1.jpg?width=4032&format=pjpg&auto=webp&s=6a74d5157d5fc9af97357dc06ee1471fe8b5e562

21 comments · 100% upvoted · other discussions

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[deleted] 2 points · Mar 2025

Take a core sample

Sea_Airline3506 1 points · Mar 2025

I like gardening.

[deleted] 1 points · Mar 2025

1/4" is 1/4". It's not nominal framing materials which aren't the same.

marktastic [OP] 1 points · Mar 2025

So less likely that they used it then?

[deleted] -4 points · Mar 2025

Ask for pics. Any reputable installer takes progress pics imo. But most likely they used it if they say they did. Check dumpster for cement board scraps.

marktastic [OP] 0 points · Mar 2025

The thing is, I peeked in on them briefly a couple of times and never saw any hardi board, just looked like mortaring over the basement concrete. I didn't take any pics though. I assume they didn't either since they would have brought it up as proof. So I'll probably lose this "he says/she says" argument.

[deleted] 2 points · Mar 2025

If it's over concrete you're probably fine. It's been a standard for years before they came out with uncomplicated membranes. They didn't put cement board on concrete tho. If it's not a shower you're fine.

Beef410 1 points · Mar 2025

I swear i measured hardie backer 1/2 and it was just under. Kinda i why i went with durock since it measured real 1/2. I just diy though

Free_Ease_7689 1 points · Mar 2025

Pull a piece of base and check it out. If there’s no base board I can’t imagine there isn’t one spot where you can if they used it or not.

marktastic [OP] 1 points · Mar 2025

There is a little bit by the toilet flange, I definitely don't see any hardi, just a lot of mortar splooge, same with any of the little bits of exposed areas between walls. Inconclusive at best.

Mammoth-Tie-6489 1 points · Mar 2025

Your ruler doesn’t start at zero, there’s an 1/8” extra on there making the total installation closer to 5/8”, I would bet that they put hardie down will little or no mortar bed, but it would be hard to get that 5/8” tall with no hardie

marktastic [OP] 2 points · Mar 2025

Look at the picture where I put the tile on a quarter inch piece of wood. That's already a little bit taller than the tile installation with zero mortar. I saw them using either 3/8" or 1/2" trowel.

I mean, the tile installation would fail pretty quick if there was so little mortar. The concrete is definitely not flat because there are patches of uneven cement from work a plumber did. I was moving a washer and dryer over it and it was pretty solid.

Mammoth-Tie-6489 1 points · Mar 2025

Sounds like you have your answer then, good luck dealing with it 👍

Ok_Figure7671 1 points · Mar 2025

Why would they use hardie board on concrete?

marktastic [OP] 1 points · Mar 2025

To charge me more money is the best I can figure.

Sytzy 1 points · Mar 2025 · PRO

Do you have a floor vent to look through?

marktastic [OP] 1 points · Mar 2025

Unfortunately not, it's on the basement slab.

Sytzy 1 points · Mar 2025 · PRO

I caught into that after I look further through this slab. We install tile commercially on bare slabs all the time unless a membrane is called out for us to use. But yeah, if they’re charging you for it, that ain’t right. 1/4” thinset+ 1/4” hardboard + 1/4” thinset + 5/16-3/8” tile should be easily an inch or more if they used it

shermanhelms 1 points · Mar 2025

1/4” hardi is basically 1/4” thick. Then you have the mortar under the hardi and the mortar under the tile. Usually works out to about 1/2” not including tile. There’s no way they put hardi under there unless they just screwed it to the subfloor with no mortar and then sett your large format tile with a v-notch trowel.

marktastic [OP] 1 points · Mar 2025

I definitely saw them use a trowel with notches bigger than a quarter inch.

Is it normal to screw the hardi into the basement concrete floor? That's what was tiled on.

shermanhelms 3 points · Mar 2025

No way they used hardi then. Possible they used an uncoupling membrane but doesn’t make sense that they’d lie to you about it. Most UMs cost more than hardi.