1/2 Hardibacker Floor?

Page 1 of 2  
Typical kitchen floor, but only 1/2" plywood subfloor instead of 5/8". The subfloor is kind of springy, I think. I suppose the best way would be to pull up everything and replace it with 3/4" tongue and groove, but I'd have to remove cabinets, etc. So what I plan on is adding 1/4" plywood for a bit of strength to the existing 1/2", using staples and glue (liquid nails), and then adding 1/2 hardibacker. The height then matches the old floor and I think it'd be pretty strong for ceramic tile.
Sound good?
Another thing is that the hardibacker half-inch stuff is labeled for "walls", but was sold to me as being for floors. I'm told it's the same stuff. And the website for Hardie says the hardibacker 500 is primarily used for walls, while the quarter-inch stuff is for floors.
Why? Am I making a mistake, or will I just have a level, stronger floor? (thinset mortar on top of the half-inch HB, for 12x12 ceramic tiles)
Still sound good?
TIA!
Mark
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It'll be fine on the floor.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 17 Nov 2003 11:03:45 -0800, snipped-for-privacy@svs.com (G. Mark Stewart) wrote:

Maybe. From what I have read, the concrete or hardibacker substrate is NOT considered to add ANY structural integrity to the floor. As an engineer, I'm not sure that I fully buy it, but hey, my background is aerospace, not construction materials.
Perhaps a better solution would involve gluing and screwing 1/2" AB or AC exterior ply to your existing sub and using 1/4" backer. Your end buildup would be identical.
Might want to check in at John Bridge forums, or at a proper tile/stone purveyor, for a more professional read on this. I do know that the thinset adhesives are rated by deflection. If it feels springy, it likely isn't ready for tile.
David Glos
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@hotmail.com says...

In the design of concrete structures concrete is assumed to have ZERO strength in tension. Concrete is riddled with microcracks that make it unreliable in tension. Therefore, bending stresses in concrete structures must be carried 100% by the reinforcing medium. If the hardibacker does not have steel (or other) reinforcement to withstand the tension forces in bending, don't use it for flooring.
Rick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Java Man (Espressopithecus) wrote:

So typical for ahr these days. 2 idiots discussing a product that neither knows anything about.
--
Liam


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If you don't agree, why not do something constructive and tell us why? Are you afraid someone will find fault with your advice?
Rick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 18 Nov 2003 22:00:36 GMT, Java Man (Espressopithecus)

Liam is a lot like another guy who used to post here. Lots of advice about the posters, little advice about the OP's questions.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@nowhere.not says...

I hear you, but Liam may have had a point about my post. If the OP to whom I was responding didn't intend the Hardibacker to span between joists, but only to sit on a suitably stiff sub-floor, it is probably OK. My guess is that Liam could probably be pretty helpful if he wanted to.
Rick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 18 Nov 2003 22:19:46 GMT, Java Man (Espressopithecus)

Yep, he's right about the deflection issue. That's the real concern.
Point is that he doesn't have a good day unless he gets to flame three posters in ahr. If he gets to show off his tiling knowledge at the same time, even better for him. Too bad he can't provide the tile knowledge without the acid remarks.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jimmy wrote:

At least he has knowledge to impart. Quit acting like a whiney wuss and take from it what you can.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

I'm a little lost here -- what else could it be? Surely no one uses the backer board without a decent sub-floor under it, right? Like I said, if there's some detail you need that I've left out, I'll do my best.

All I have is a first impression that he, as well, should seek out the help of a pro.
But tantrums aside, I'm curious about a couple things. Firstly, I didn't see anything on the Hardie website to indicate that 1/2 was weaker than 1/4. In fact, the brochure in the store stated that 1/2 was dimensioned to replace 1/2 sheetrock, and 1/4 was dimensioned to minimize the rise of the floor surface, no other indications.
Secondly, it seems to me that adding the 1/4" to 1/2" and gluing is less strong than a single 3/4" layer. But that this is assuming that the glue used is weaker (more sparsely applied) than the bond between layers of plywood. Am I right or wrong, here?
TIA!
Mark
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"G. Mark Stewart" wrote:

Go back to their site and look at specs. Strengths are given there.

What's the dif? Adding the 1/4" to 1/2" still produces an inferior substrate for ceramic.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jimmy wrote:

Fuck you and the other guy both big mouth. Let's hear some specific advice that will assist the op. Otherwise fuck off and die cockroach.
<squash>
--
Liam


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Hey I did give useful advice (namely thicker plywood, thinner backer), and did it in my usual self-deprecating way. For that, you called me an idiot that had no clue. My advice was based on his original post which indicated his floor was "springy". Obviously a highly subjective term, but suggestive of a floor that needs a little structural help before laying tile.
If I remember correctly ;-) maximum substrate deflection for latex modified thinset is L/360 for tile and L/720 for natural stone. According to their manufacturers, and the tile council literature I have read, concrete backer board and Hardibacker are not considered to structurally reinforce the floor. On the other hand AB and AC exterior plywood is considered a structural improvement.
And yes, I have laid both tile and natural stone floors, and done it right; namely, proper substrate reinforcement, backerboard selection, and thinset use.
DLGlos
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Java Man reared up on his hind legs and bellowed in agony:

My advice was already given. In your haste to 'impress' the other big mouth you must have missed it. What you call 'advice' is mere chatter. Borrowed from a book or a website and better suited to a chat group where you don't need to be specific.
--
Liam


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
G. Mark Stewart wrote:

Hardibacker underlayments add density and that's what you need. However, you give no detail as to how your floor is built. Hard to get specific help without giving specific detail. Also, contact Hardi with your primary question.
Your first concern should be the following. http://www.ttmac.com/deflection_limitations.htm
--
Liam


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Oh, coupla' things I forgot to mention in reference to some of the exchanges. First, thanks for all the help and input. Secondly, in reference to the structure of hardibacker board, I noticed one of the sheets I rejected from the pile at Home Depot had been damaged, apparently, but something really heavy and round. The Hardibacker did NOT crack (it's supposed to be score-and-snap cuttable, so this was a surprise), but deformed around the impact with four visible layers somewhat separated and "stretched" around the blow. Not clear what it's made of -- take it for what it's worth. And, contrary to what one of the salemen told me, it does seem much cleaner and stronger than wonderboard.
Mark
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

What else do you need? By typical floor, I mean 16" centers, 2x8 joists. Not sure what details I left out of the fist post. The span of the 2x8s is about 10 feet.The joists themselves are in fine condition.
Mark
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
G. Mark Stewart wrote:

First off zipperhead, we don't know what you mean. And there's no such thing as 'typical'. Case in point; it's NOT typical to use 1/2" plywood for subflooring. Unless you have a mobile home. Case in point; you haven't told us if it's a mobile home. you haven't told us shit. We're supposed to guess what you have, and what the conditons are, etc.?
You're asking for help in a usenet group that's worldwide. Okay, for the most part nationwide, but the point is we can't see what you have. We don't know the age of your house. We don't know the area you live in and what may be 'typical' for that area, those builders, those inspectors, nada. We don't know anything until you tell us.
Use the L/360. And bottom line, that subfloor you have is crap. I recommend no less than 3/4" subfloor with 1" mortar. or at the very least, 1" plywood subfloor with 1/4" Hardi.
Your 1/2" crap and 1/2" Hardi over it (which if you'd bother to take the time and look at the specs on their website, actually has less strength than the 1/4") is substandard for ceramic tile installation. Good luck.
Hire a pro.
--
Liam


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

This does pretty much sum it up and is good advice. A minumum thickness is required. Just getting that thickness is not enough alone, the L/360 formula is to determine the overall flex. Too thin a substrate = failure. Too much flex = failure.
My advice (way back in the thread) was probably too brief... it's OK to use Hardie 1/2" inststead of other 1/2" products as long as _all_ requirements are met.
If someone can't figure out to apply L/360 or determine flex and stability... they should hire a reputable, professional tile setter.
Just adding a 1/4" sheet of plywood and 1/2" of some backer board to gain minimum thickness has all the signs of a job headed for failure due to not understanding the overall picture.
J.P.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.