The wife and I recently had an accident with the washing machine that
flooded our kitchen. This required the vinyl to be pulled up along
with the plywood underlayment exposing the subfloor, which is
Engineered Wood. We felt this was a great time to upgrade to a tile
floor and felt that we would be able to tackle the task ourselves.
After speaking to people from Lowe's and Home Depot, they suggested
that we use the 1/4" Hardibacker EZ Grid product as an underlayment to
the tiles as it is lighter, easier to cut and compable in durability,
water resistance and strength. We purchased it, began the install and
were about half done when I ran into the guy that built my house. He
said that we should have used 1/2" Durock and that we will experience
problems with the Hardibacker. After this dicussion I called one
other Contractor who said the same thing. Has anybody else had the
same problem? Has anyone had problems with the Hardibacker in
general? If I truely need to use the 1/2" Durock how do I remove the
Hardibacker I just laid down? Any help would be greatly appreciated.
Other than the thickness, what's the problem or projected problems? If you
have a sturdy subfloor, and installed the Hardibacker according to
directions, I don't see a problem. I just used Hardibacker on my new kitchen
countertops. 1/4" was OK, I installed over 3/4" CDX plywood. Hardibacker is
set in thinset AND screwed to plywood. I felt 1/4" was good, we're not
walking on the countertops! BTW also installed ceramic tile over Hboard. and
Dennis J Sunday
Home Inspection Systems
The issue is how much deflection will the floor have under use. This
determines if your floor will crack. If the deflection is better than
1:480 you're probably ok.
Bear in mind that for the same material properties (modulus), doubling
the thickness reduces the deflection by a factor of 8. This makes 1/2"
material 8x stiffer than 1/4". I don't have data but my sense is that
Durock is stiffer (higher modulus) than Hardibacker.
My own preference is 1/2" Durock over the plywood underlayment.
I was just concerned that two professionals suggested the Durock while
the two retailers recommended the Hardibacker. Normally I would trust
the professionals because their livlihood is at stake and if it turn
bad then the retailers just say 'Oh well'. Wanted to see if anybody
else went the route I did and what if any problems they had.
On deflection, I know the formula is l/360 or something similar to
that but how do you measure it?
BTW. Thanks for the replies.
Measure it with as tiny ruler.;-)
Actually the easiest way to get an idea of how much movement you have is
to stretch a taught line over the floor that is secured to the wall on
either side of the room (perhaps a 12 ft or greater span.) If you then
hang a light weight in the center that just touches the floor and walk
over the floor while someone monitors the gap between the weight and the
floor you'll see if there is any movement. What you want is less than
0.03 inches (1/32") movement up and down.
If you have a laser pointer and can mount it so that it doesn't move
then point it at an angle at a small mirror on the floor. Locate the
laser pointer close to the mirror and reflect the spot on a wall distant
from the mirror. Using simple geometry the reflection of this spot on
an adjacent wall will permit you to determine the floor movement.
My preferred approach though is to calculate the floor deflection from
I tiled my kitchen last spring...I went with the Durock as an
underlayment....it is messier than the Hardibacker but I thought that it was
more durable and better able to handle any water (hopefully none..ever)
better than that hardibacker. as far as deflection I installed the 3/8"
Durock right on top of a 3/4" t&g subfloor. Glued and screwed it down. The
tile has held up perfectly...no cracks etc...I've been very happy with it.
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