Hi Martin:

I just finished ripping out the old tile floor in my bathroom. The
builder used 2 layers of 5/8" plywood, just as you suggested. However,
at every plywood seam, the tiles cracked because of seasonal expansion
and contraction of the plywood. Because of this, I will never
recommend installation of tile directly onto plywood.

I have replaced the upper layer of plywood in the bathroom with a layer
of 1/2" Durock and a layer of 1/4" Hardibacker (it had to be at least
5/8" thick for cosmetic reasons). It feels like a concrete slab, now.

Three years ago, I replaced the hardwood floor in my laundry room with
tile. I used 1/2" Durock on the 5/8" subfloor, and have had no issues
whatsoever with the floor. This room sees heavy through traffic every
day, and a heavy, vibrating washing machine.

Regards,
John.

Martin wrote:
Hi,

most places (literature) I looked, durock is recommended as a
subfloor for
floor tiles. I have currently 5/8" subfloor, and was gonna screw on
5/8" on
top of it to get the recommended 1-1/4" for plywood subfloroor, but
now i am
not sure if I should skip the 2nd layer and just install duroc. The
main
reason to go with plywood is that I have about 5 sheets of it. The
main
reason for duroc, is that it is thinner, and wouldn't increase the
floor
height so much. Plywood is supposed to be flexing more, but if you
secure
it at recommended intervals with proper screws, is that still a
problem?
So my questions a
1 - are both options acceptable? (1-1/4" plywood) or 5/8" plywood
with duroc
on top?
2 - is the durock instead of plywood going to make huge difference?

The area to cover is cc. 100sqft, - 28 sqft for tub island.
Does the additional flooring need to go under the tub island, or can
the
island rest directly on the main subfloor?


Thanks.

m.