Self leveling compounds are
the perfect solution for leveling out uneven subfloor surfaces that you plan to
tile. Concrete floors are notorious for having high and low spots and not being
level. Tilling over them, without first applying a self leveling compound, is
fraught with problems. The ceramic tiles will end up not sitting evenly over the
concrete floor, and thus will be susceptible to breaking or becoming loose over
time. In addition, the unevenness in the floor will show through on the tiled
floor surface. Tiles will have high or low corners and grout lines will look
uneven. Wood subfloors can also be a problem.
Floor joists that may have
twisted or flexed over time may cause the plywood subfloor to become uneven.
So if you have a ceramic floor tiling project, and the subfloor is not perfectly
level, apply a self level compound to the subfloor first and allow it time to
fully cure. As the name implies, self level compounds will fill in the voids in
the subfloor surface such that it becomes smooth and level.
Preparing a Subfloor for the Application of a
Self Leveling Compound
Prior to pouring a self leveling compound onto the subfloor first make sure that
the subfloor is firmly fastened down and rigid, and that it has been swept and
vacuumed of any debris and dust. If the subfloor has any level of deflection
when you stand on it, both the self leveling compound and floor tile will end up
cracking over time. Note that the self leveling compound will add no structural
rigidity to the subfloor. Similarly, if there is any debris or dust left on the
subfloor the self leveling compound will not adhere well to the subfloor
After sweeping the subfloor
surface go back and vacuum it with a shop vac, such as the
Shop-Vac 962-16-00 16-Gallon Wet/Dry Vacuum.
Then use a slightly damp mop to wash the subfloor surface. Again, it is critical
that there is no loose material on the subfloor prior to applying the self
Application of Primer to Subfloor
In order to ensure that the self leveling compound will bind well to the
concrete or plywood subfloor, you first need to apply a special latex primer to
the subfloor surface.
You can either roll or brush
the primer on. When applying the primer make sure that you work it in to every
nook and cranny of the subfloor surface.
After applying the primer allow it to dry fully before pouring the self leveling
compound onto the subfloor.
Mark the Low Areas on the Subfloor
Using a framing square or level, slide it along the surface of the subfloor to
identify the low areas. Mark or circle the low areas with a pencil. You will
apply the self leveling compound to these areas first.
Prepping the Self Leveling Compound
It is important to understand that self leveling compounds set up fast. It
typically sets up in ten to twenty minutes. Thus you have to be quick with the
mixing and application of it. So make sure you have all of your tools and
materials near the jobsite prior to mixing the water with the self leveling
Since directions can vary with self leveling compounds make sure to read and
follow the directions carefully on your package of the material. Also keep in
mind that you should not breathe in self leveling compound dust. As a result,
make sure you adhere to all of the safety precautions listed on the directions.
For example, you may want to wear a mask and gloves when mixing up the self
leveling compound, and you should always were safety goggles.
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Since time is of the essence
when working with self leveling compounds you may want to use a power drill and
mixing hook to speed up the mixing process. The
DEWALT DC759KA Heavy-Duty 18-Volt Ni-Cad 1/2-Inch Cordless Drill/Driver Kit
is ideal for mixing up self leveling compounds. Mix the self leveling compound
in a clean 5 gallon bucket with cold water. As a matter of fact, preferably use
ice water, minus the ice, when mixing up the self level compound. The cold ice
water will help to extend the working time of the self leveling compound
mixture. Make sure the mixing hook hits the sides of the bucket when mixing it
to ensure that all of the self level compound material gets thoroughly mixed
with the water.
Youíll know the self leveling compound mixture is ready when it has a loose
soupy consistency to it. If it is too thick the curing time will be shortened,
and if it is too loose youíll have trouble leveling out the subfloor with it.
Try to limit the mixing time to less than three minutes to ensure you have
sufficient enough time to pour and spread it.
Application of Self Leveling Compound
After you have achieved the proper mixture consistency, immediately begin to
pour it onto the subfloor. However, first pour it into the low areas that you
marked with your pencil. After pouring a little bit of the self leveling
compound mixture into the low spots allow it to spread out a bit on its own.
Then use a trowel or squeegee to flair and smooth it out. Again, youíll need to
work fast as you only have around ten to fifteen minutes to work with it. Then
continue to apply the self leveling compound to the rest of the subfloor surface
Photo by Mark Donovan
After youíve made the mixture do not attempt to thin it out to stretch the
material or extend its working time. This will lead to the self leveling
compound not curing properly, which will result in eventual cracking. If it
cracks, the ceramic floor tiles will eventually loosen up.
In less than an hour the self leveling compound will have set up and be firm to
the touch. After four hours it will be hard enough to walk on. However, hold off
for 24 hours before tiling the subfloor to ensure that the self leveling
compound has fully cured.
Clean Up of Tools
Immediately after pouring and spreading the self leveling compound wash your
tools and bucket out thoroughly. If you fail to do so they will be unusable for
the future, as the self level compound will be glued solid to them.
So thatís all there is to it to applying self leveling compounds to subfloors.
Good luck with your ceramic floor tiling project.
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