I'm about ready to lay down the backer board on my counter tops so I
can lay the 18" granite tile down.
I don't really understand backer board though. It wants to be snapped
in straight pieces which would leave seams between them. Particularly
around the sink. Do you do anything with the seams, or not? I'm told
liquid nails to glue the backer to the plywood, is that right?
I think you are probably fine for a counter top. I would try to
prevent a tile seam from landing directly on top of a backer board
seam. There are tile mortars that work well for attaching tile
directly to plywood or mdf. I would use one of those rather than
liquid nails. I did not use backer board where I put tile up as a
back splash. I might not use it for a counter top either if the
existing surface was rigid enough.
They make an open mesh tape for seaming backer board. I use tile
motar and screws to put backer board on the floor. I leave about 1/4"
between backer boards. Put the tape on then force some of the motar
into the gap between the backer boards. You could do the same on a
On walls I use Durabond to fill the seams. That would work fine for a
countertop also I think. On floors I use thinset and let it dry before I
lay the tile.
You must have at least 3/4" off plywood as your base for a counter so a 1"
roofing nail should be fine for nailing the backer board to the substrate.
I use roofing nails or ring shank nails for laying the stuff on the floor.
The nailing pattern for a floor is fairly close; on a counter I am sure you
can get away with less.
Are you using thinset or mastic for the tile to backerboard glue? The
mastic is easier to deal with in a small area like a countertop.
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I'm not the one doing the tiling, but I was thinking thinset as there
will be some water near the sink. How much space between the backer
board pieces? 1/4" as LJ suggested?
I've had trouble with *anything* to do with water. I may be unduly
I only use the Hardi product and haven't done any for over 5 years. I seem
to recall that 1/8" gap was the recommended amount. Where ever you buy the
materials should have installation instructions for free. If not the MFG
will have them online.
For a counter I seriously doubt that you need to float the board on a bed of
thinset before nailing.
BTW, if you aren't doing the tile yourself your instructions should come
from the person who is doing it. This is for your protection in case things
don't go right. He said, she said, Colbyt said isn't worth a darn when
dealing with a local contractor.
That, had not occurred to me:
The hardi backer I got was just dropped off a forklift.
The "installer" is an artist friend who has tiled a lot of things and
I don't think a countertop has been one of them. She just said to glue
it down with liquid nails and I can't reach her right now. I've been
trying to get this done so I can at least have a kitchen sink again.
I've been redoing my '29 kitchen and there has been a lot to do
(subfloor, new floor, fix plaster and paint, new plumbing, wiring, make
cabinets and counters...), some of which I just have a faint grasp of,
or none at all! With that said, it is coming along and I'm happy. I'm
resourceful, but I'm also sometimes clueless about how the "pros" do it,
so I ask...
1. Nail or screw the 1/2" cement board to the plywood counter top. Space
fasteners about every 6-8". As long as the ply is reasonably flat you don't
need thinset under it. Joints between pieces of the cement board are
unimportant, anywhere from touching to 3/8" would be fine.
2. If there are spaces between the pieces of cement board fill them level
with thinset. No tape is needed. If there is a difference in height
between pieces of cement board, level with thinset and a swipe with a broad
knife to feather. Let thinset dry a day if you have to do the latter.
3. Dump a bunch of thinset on counter and push it around with the straight
edge of the trowel covering everything then use the correct comb size
4. Lay tile. As you do, check for level from piece to piece; if needed, tap
high one lower.
5. Let tile set for at least 24 hours then grout. Be smart, don't use
white. Get *ALL* grout off of tile faces.
6. Let grout cure for at least a week then seal.
Hardie requires a thinset bed under their products, according to their
installation instructions, for both the 1/4" and 1/2" (0.42") stuff.
Durock does not, but they specify putting plastic under the
backerboard (?). Kind of odd.
Why would you omit the tape? Particularly if you're not using a
thinset bed? Durock doesn't specify a thinset setting bed for any of
their thicknesses, but everyone requires taped joints. That's the
only place that differential movement will happen, so leaving the tape
off - all 30 cents and five minutes of it, seems to be an odd place to
save on cost/labor.
To the OP: RTFM. Whatever the manufacturer of your backerboard tells
you to do, do it. They make the stuff, so they just might know a
thing or two about it, and all backerboards are not created equal.
Yeah, and for the hardie stuff that I got earlier in the year, it was
printed on the actual sheets, too. I think 1/8" was right. I screwed the
board down at 8" spacings, with 4" at the edges. Thinset and tape for the
I used the cheap grey thinset. Not for adhesion but primarily as a level
bed without voids once dry. Backerboard screws as per the pattern
provided with some extras on edges many edges. All done while thinset is
wet of course. 1/8" between board edges. No three corners at one
When the tile goes down it's done with quality thinset and joints are
backerboard taped imbedded in the tile thinset.
After grouting I let it dry a FULL 3 days before sealing the grout with
this stuff. Like $50 a pint but it goes a long long way.
All is good so far but it's only been a few months.
Sounds like a good installation - I'm sure you'll get a lot of years
out of it. Probably someone else will, too.
You're right about the thinset under the backer board being a setting
bed that eliminates voids, and it's a critical step. A friend had a
contractor redo a bathroom and he didn't put anything under the backer
board, and compounded the error by setting the tile on dry backerboard
and using too much water to clean up after grouting. I stopped by
during the installation and mentioned the issues, but, you know how it
goes, they didn't want to upset the contractor. I told them that
they'd probably get six months before the grout started cracking, and
sure enough, last time I stopped by I could see the grout was giving
up the ghost. There's no point in using good materials if someone is
going to ignore the manufacturer's instructions.
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