TERRAZZO TILE AND MARBLE ASSOCIATION OF CANADA
|
|
|
You
Want Me to Install on Top of That? Not
that long ago, it seems, that the average job was 106 mm wall tile
installed on concrete blocks, and a 150 mm x 150 mm or 200 mm x 200 mm
monocottura tile, thin-set to a new concrete slab.
Nowadays, this is the exception, with tile formats becoming
increasingly larger and thinner and the installations being required
over substrates that cover a broad spectrum of surfaces.
Newer buildings are more lightweight, being constructed of
space-age materials, thinner gauge steels, and suspended slabs that
vibrate when you walk across the span.
Renovations of existing buildings require installation over
previous installations, with all their inherent problems.
Pity the poor setting material manufacturers who are challenged
constantly to provide the suitable setting material to bond a rigid
ceramic tile to a surface that literally is in constant movement.
And let’s not forget the installers, who are required to
guarantee the installation over all these various substrates. Whether
you are the designer of the system, or the installer of the system, it
is very important to take the time to analyze the situation and make
sure that all potential problems are examined, and the proper measures
taken. An ounce of
prevention is really worth a pound of cure in these cases and some of
the following procedures may save you a ton of trouble, not to mention
the money you’ll save in warranty repairs. Carefully examine
the area involved. Note
the position of the control and expansion joints in the slab.
Are there any structural cracks apparent? If
it’s a new slab, has it been allowed to cure for at least 28 days?
Was it poured in the winter, with heating by a combustible
fuel? Was a hardener or sealer
applied to the slab or did the painter spray the ceiling and get paint
all over the floor? Look
at the tolerances in the level and straightness in the slab and make
sure it conforms to industry requirements.
If it’s a renovation or an overlay, know what the composition
of the surface is. Is
there delamination of the surface?
A simple chain drag will tell you a lot about the substrate.
Areas that are not solid must be corrected before installing
the new surface material. Remember
that the strength of the whole system is only as strong as its weakest
point. Once
you’ve made this survey, it’s important to plan your installation,
taking all the information you’ve gathered into account.
Examine the size and pattern of your tile, how they line up
with existing expansion and control joints and how the new control
joints will line up with the old ones.
You may have to consider the use of crack isolation membranes
if the new and old control joints do not align, or if you are expected
to tile over some old cracks. Expansion
joints in the structure must be carried through to the surface of the
finish. You have to
predict where movement may take place, and take the appropriate
measures to prevent random cracking in the new surface. Variations
in the surface may require some straightening work before starting the
actual installation. Make
sure that you use a product which is compatible with the setting
material you intend to use, and whose bond strength is at least as
great as the proposed setting material.
Remember that the entire system is only as good as its weakest
link, so a cheap sub-floor preparation material will compromise the
entire installation. Floor
preparation is a key element to ensuring the success of your
installation. Even if you
use the highest rated setting material, trying to adhere to an
improperly prepared floor is like playing the Lotto....you lose more
often than you win. The
presence of any foreign substance such as old glues, sealers,
hardeners, and cement laitance will result in certain failure.
Setting material manufacturers generally recognize that shot
blasting existing surfaces is usually the best way to achieve the best
preparation of the surface. Use
the appropriate setting material for the type of substrate as well as
the type of material being installed.
If the surface of the material being installed is dense and
smooth, or if the surface to which you are adhering is smooth, you
must achieve a higher degree of chemical bond than normal.
This is normally achieved by using thin-sets with liquid latex
additives, or better yet, with epoxy setting materials.
Polymer modified mortars will give you slightly less bonding
strength, and thin-sets without any additive will give very poor
adhesion under these conditions. As
well, using the right trowel can be critical.
The notches on the trowel must be just the right size as to
allow full coverage once the tile is installed, yet not too large so
as to make installation a messy affair.
Backbuttering larger format units will usually increase the
likelihood of full coverage, and under some conditions, is imperative
to ensure a proper, problem free installation.
And full coverage will eliminate those cracked corners that
mysteriously appear after the job is finished. Allow
sufficient time for the setting material to achieve enough strength
before allowing other trades on the floor.
If the chemical bonds are broken during its cure, they won’t
magically grow back, and you’ll surely have some loose tiles on your
hands after the job is finished.
Unless you’re using fast set bonding material, three days is
usually required before allowing light traffic.
If the material being installed is sensitive to staining and
scratching, make sure the general contractor seals the floor and
protects it from other trades once you’ve finished. A
successful installation is dependent on following these common sense
steps, not cutting corners, and following TTMAC guidelines for
installation. When in
doubt, ask for information from the TTMAC office, or from a TTMAC
member. So now, go
install on top of that! Jim Mannella is President of National Ceramic + Granite Limited of Montreal. He is a Past President of the Terrazzo, Tile and Marble Association of Canada, and has been a Director of the Association for many years. |