# Hardi Backer Board...???



## dgrabs (Apr 5, 2005)

Hi all,
Just a basic tiling question. I am re-doing the kitchen floor, and am planning to use 1/2 thk Hardi-Backer board for the sub-floor preping (I used it before for a shower stall and works nice - with 4 mil poly...) and I was interesting in knowing a couple of things:
1. - is it necessary to remove the existing vinyl floor before screwing down the backer-board?....there is 3/4 in plywood underneath
2. the subfloor has settled now, and there are some shallow troughs that will be spanned with the backer board. Has anyone heard of any 'flexing' issues with hardi-backer board that I missed?
3. The building codes are standard residential for Pennsylvania...I don't believe there is a weight issue, but it doesn't hurt to ask....


Any response is greatly appreciated....and any tips are always welcome......


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## Mike Finley (Apr 28, 2004)

Well, here we go again, but I'll jump in and say, no removing of the vinyl is not a standard requirement. However there may be surrounding issues that would mean removing it would be prudent, however if conditions are right removing of it will gain you nothing other than 1/8 inch.

The shallow troughs doesn't sound good. You don't want backer board spaning any troughs of any great width. But without seeing it is hard to know exactly what you are dealing with. Small troughs would be taken care of by the thinset spread under the backer board somewhat. You basically want the backer board to be laying directly in plane with the sub-floor.


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## R&D Tile (Apr 5, 2005)

You want to do this correctly?, remove the vinyl and any 1/4" underlayment that might be under it, then find out the size of those joists, their spacing and length of the unsupported span.

There shouldn't be any flexing in the floor, let's first see if the floor meets specs for tiling, then we'll see which is the best way to get it flat for tile before adding anything.


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## bergenbldr (Apr 23, 2005)

everthing you need to know to install hardibacker is on thier website .3/4ply is fine.hardibacker requires aplywood subfloor a tg board subfloor cannot be used with hardibacker in floor applications.


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## R&D Tile (Apr 5, 2005)

Your floor needs to meet L/360 minimum for ceramic, 3/4" plywood is minimum over 16" spaced joists, spaced further apart, then you'll need 2 layers of ply.

Plywood only solves the flex between the joists, not the overall flex in the floor, which is why the above information is important, Hardies website will only tell you what you have to meet as specs are concerned, not on how to solve them or what you'll need.


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## bergenbldr (Apr 23, 2005)

100%correct. i didn't mean to suggest that the hardiebacker manual would instruct on how to frame or reframe a floor to meet code.


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## R&D Tile (Apr 5, 2005)

:Thumbs:


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## dgrabs (Apr 5, 2005)

Thanks for all the input. The joists do meet the 16" spacing requirement. It was the "troughs" between the joists that I was concerned about (by spanning them with the backer-board). The floor itself is solid, the flexing was in reference to a possible problem with spanning the troughs (which are relatively shallow - but still noticeable).... I will look at hardi's site, but I'm fairly certain the settling that I was referring to is comon-place. I just wantged to make sure....and all your input has helped a great deal. Thanks!


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## Tileguytodd (Apr 4, 2005)

As everybody here will be finding out in the near future,the L/360 requirement is likely going to be thrown out by the TCA/NTCA very soon.
One of the reasons for this is that it does not deal with between the joist deflection which has much more bearing on installation failures than over all spans.Meetings were held in Orlando regarding this issue during coverings and it looks as if it is going to go through.

Now, that said, we need to understand 1 thing with this installation above and that is that Hardibacker as with any CBU has virtually no structural strength adding no structural value.Using 1/2" hardibacker (or any CBU)and not removing the vinyl means you are 5/8" above the 3/4" subfloor(if there is no 1/4" underlayment)
Removing the vinyl,adding 3/8" plywood and using an uncoupling membrane like Ditra (1/8" thick)will give you a much stronger floor System and a far better installation without creating added height problems.
As mentioned above, more information would help to determine the overall situation you have(you have recieved some very good information above) (way to go Rich  )
The future is going to hold some changes in much of our thinking processes regarding structural requirements for ceramic installs.We should know more within 90 days as any decision requires I believe 60 days of public comment before changes are enacted.
Comments??


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## dgrabs (Apr 5, 2005)

After checking it out online, looks like using the 3/8 plywood and DITRA is a better solution than the Hardi-Backer board in this case. Of course, I'd like to do a perfect job, but there are some compromises...ie. time. So I may leave the vinyl in place and install plywood directly over it, since height is not that big of a concern. Since the DITRA has air-recesses to allow for evaporation, and is not tightly coupled to the sub-floor, this may be my best option. I've heard so many bad stories about removing vinyl floor glue that I'd rather not bother. 

Thanks, all!


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## R&D Tile (Apr 5, 2005)

Then be aware that if you leave the vinyl, you might be ripping up that new tile floor in the future, think what a mess and cost that will be.


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