The term self-leveling has always seemed
like a bit of a misnomer to me. It is most commonly used to describe a broad
category of cementitious products which when poured in a semi-liquid state, aid
in bringing otherwise deficient floors into either a flat or level condition.
The large size tiles and patterns popular today make floor flatness a critical
issue in most ceramic tile installations.
Unlike many other flooring
products, the rigid nature of ceramic tile does not allow it to conform to any
type of surface irregularities. With each job, some means of correction will
have to occur. Correcting out of plane (not flat) conditions requires careful
evaluation as it can become very expensive in both product and labor
categories.
Retailers
often wrongly expect that all the corrective measures required for providing
flat lippage free tile work will be automatically included in the standard
installation price and are often very surprised to learn there may be some
additional charges.
Speaking for myself and others in the
installation community, we try to be just as accommodating as possible but at
some point we occasionally have to put ourselves in the uncomfortable position
of saying there will be an additional charge for corrective work. So if making
the floors flat is not our job just whose job is it?
Published recommendations for ceramic
tile come from a variety of sources. The tile industry, through the Tile
Council of North America (TCNA) and the American National Standards Institute
(ANSI), provide the portion related directly to our trade and are known as the
TCA and ANSI Handbooks.
Part of those recommendations are that floors and walls be
on plane or “flat” within 1/4” per 10-ft. and have no greater variation than
1/16” in 12-inches. Tile floors and walls do not have a level requirement, only
a flat or “on plane” requirement. These recommendations are based on the
standards published by the trade associations responsible for those substrates.
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Self-leveling
products require a primer prior to application. You should always use the
recommended product provided by the manufacturer of the self-leveling product.
Chemically, there is variation between products; they are not “universal.”
Photo courtesy of MAPEI.
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In the
concrete industry, the American Concrete Institute (ACI) published
recommendations are contained in a document known as
ACI 302 (available at
www.concrete.org).
You will also find similar reference for tolerances in a
document published by the American Plywood Association (APA or Engineered Wood
Association) known as the
Design Guide (available at www.apawood.org). APA recently became the
accredited standards developer for wood products by the ANSI.
For gypsum wall products, the tile industry draws the
recommendations from a document known as GA-216,
published by the gypsum industry. Flatness requirements mentioned in the TCA
handbook are not TCNA recommendations; rather, they are adapted from those who
provided the substrates. For those of us doing new construction under contracts
and with specifications, those documents are your bibles.
But what about remodeling and
renovation? In the real world referenced or not, expectations still exist —
people want and expect flat floors free of lippage. Here the installer assumes
the responsibility of correcting any tolerance deficiencies that may affect the
installation. His guideline comes from references made to standards or
manufacturer recommendations printed on nearly every bag, bucket, or box of
setting materials and related items I have ever seen, with few exceptions.
Let’s just forget about who is
responsible for what for the moment and focus on the basics. Bottom line:
customers want flat floors free of any lippage. They want floors with very
small grout joints perfectly aligned, straight as an arrow for long distances.
The feeling is the tiles are bigger so the work is less. There are a host of
problems with that theory. Anyone who has ever installed large tile knows the
bigger the tile, the more work to get it installed properly. We can purchase
high quality or “rectified” tile and eliminate size issues, but unless we have
a perfectly flat floor, there are going to be both alignment and height
variation issues.
Occasionally, an installer will attempt to use standard
thinset to flatten the floor. Once you get over 3/8 to 1/2” thickness with a
standard thinset, most have a very low bond and compressive strength. Medium
bed mortar that can go up to 3/4” thick are helpful, but it can be very
time-consuming to set each piece flat to the adjoining tile when you are properly
bedding the tile.
Often, you will also find a
substantial elevation change when you work your way across the room to another
doorway that brings a new problem — I’ve been there myself. Mortar beds have
always been a traditional way of providing excellent flatness and bonding
surfaces for ceramic tile but few projects are designed to accommodate the
height and or weight of a mortar bed. This brings us to a practical solution to
accommodate the needs of the installation and skills of the installer,
self-leveling products.
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Radiant
heating is a common and popular application of self-leveling products. They are
available in both gypsum- and cement-based products. You should understand the
limitations and recommendations thoroughly for each. When used with stone
flooring, a thicker application is generally recommended. Photo Courtesy of
Maxxon Corp. |
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With all the challenges of installing tile in the popular
sizes of today’s market, we can safely say self-leveling products are here to
stay. There are numerous types of products available and your choice needs to
be appropriate for not only the level of service expected but also the specific
needs of the installation.
In doing a little research on the
current stable of products available in this category, it was clear that each
product in a manufacturer’s line has different attributes. My original
intention with this article was to describe some commonality shared by all
self-leveling products.
It is accurate to say that none of the
six manufacturers reviewed for this article shared the exact recommendations in
surface preparation and mixing. The only commonality I could find between
manufactures is they all call this pumpable or pourable product self-leveler.
These are all highly engineered products with very specific performance parameters
so when choosing a product, chose wisely
These products tend to be on the finicky side and are
unforgiving of error. Priming the surface to be covered is a key component in
the success or failure of product application.
We always talk about the proper water ratio for thinset and
its importance. Many dismiss it because they can still achieve some bonding
value. Proper water ratios cannot be dismissed with self-leveling products,
they won’t bond.
Most self-leveling products are also
sensitive to slab moisture. If a slab has an elevated moisture and pH level
there will likely be bonding issues with most products. Expansion joints must
also be carried through the topping. When used in wood structures, there are
numerous cautions. Almost without exception the use of a reinforcing product is
mandatory though recommendations vary with both the service requirement of the
floor and manufacturer of product. A thin cement topping also needs room to
move with the downward deflection of wood substrates.
Perhaps the biggest misconception of self-leveling products
is that they actually level themselves. Not quite.
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Big tile can
make for some big challenges when it comes to flat and lippage-free
installations. With each job there are choices to be made. It may be grinding,
patching, a mortar bed or a self-leveling product dependent on environmental
conditions and budget. |
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Although they have the consistency of thick soup, they do
require assistance in both spreading out and tying into successive pours. A
pump is really the way to go on a project of any substantial size. Perhaps most
important is to always have adequate manpower when using these types of
products. The working time is limited and there are few jobs that can be done
with one person. Our practice was to never pour unless we had a minimum of
three people to assist, though sometimes you could get by with two. If that was
not possible, using a trowelable product would be much more appropriate and
provide fewer headaches given the limited working time of self-leveling
products.
As wonderful as these products can be,
getting paid appropriately for their use has always been a problem. It is very
difficult to calculate the exact amount volume of material required to provide
coverage for any given area. Making assumptions can be very hazardous to your
financial well being when using a product with the consistency of soup. We have
even gone as far as taking elevation readings all over the room using a laser and
still been off on our calculation enough to hurt a little so always err on the
side of caution.
Once the skills and
technique are mastered I think you will find this is a much faster approach to
correcting floor problems than squaring each tile up to the other with the
appropriate thinset mortar. It is also much easier to get compensated for as
the customer can see there is some corrective work going on that cannot be as
easily perceived when adding additional thinset to make up for tolerance
inconstancies in the floor. While this approach may not work for everyone, our
company found it to be very profitable and that’s why we work.