Floor tile can be installed over several
types of underlayment
One of the tried and true types of underlayment is an application of mud or mortor with a combination of mesh and
felt. This was once the standard, and is still used by some professionals. It is time consuming and usually above
the skill level of a do-it-yourselfer.
Concrete is another choice, and provides a very stable surface. Some preparation is needed for tile installation,
even over concrete.
It is wise, even over a concrete surface that has never had any cracks to provide an isolation membrane just to be
on the safe side. The earth is a constantly moving organism, and settling and cracking can occur at any time. The
isolation membrane will absorb this movement protecting the tile. It will probably also be necessary to rough up
the surface so the tile will adhere securely.
Today, plywood and cement backerboard are the two more popular
choices for underlayment
Backerboard is made by combining concrete with mesh or fibrous material, and is available in sheets like drywall.
This is a good choice, and often preferred for kitchens and baths, since it's design is compatible with moist
Backerboard is readily available in all the larger home improvement centers, and is modestly priced.
Installing tile over plywood
The debate goes on over plywood vs. backerboard as a tile underlayment, but many contractors still swear by plywood
and claim to have little difficulty over this decision.
But, one particularly good place to use plywood is over a resilient floor that is to remain in place. Sometimes
improvement comes with a price. Not so many years ago the resilient flooring was the new innovation. Sadly, some of
these products contained asbestos. Who knew at the time?
In many older homes this flooring remains. When a new floor is needed this presents a problem. If it is determined
that the floor does probably contain asbestos, it requires professional removal. It is less expensive to leave it
undisturbed and do your tile installation over it.
Using plywood over this flooring both covers it, and protects the tile. Though tile is a very hardy flooring, it
does not bend or flex well. Keeping it flat and intact are key to preventing breakage. The plywood will provide a
hard surface with no give in it over which the tile can be safely installed. Thinset and an underlayment should be
placed between the plywood and the tile to prevent the plywood from leaching the moisture which will result in
The above are the more common choices for a tile underlayment. A non-professional will find either plywood or
backerboard the best and easiest choices to work with.
TIPS: When preparing to lay tile make sure surface is flat without bumps or depressions that will create hollow
places under the tile. Tile will crack if not stable underneath.
If using backerboard as an underlayment for your tile installation, purchase screws exclusively designed to be used
with this product. Drywall screws will be very difficult to drive and make flush.