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My tile is bonded to
a concrete slab, why do I have cracks?
While it is impossible to speculate on the exact cause
of cracks without an inspection some reasons for cracking
include but are not limited to:
Whenever tile is bonded to concrete, movement in the
concrete will cause cracks to occur in the tile layer.
Should cracks occur in the concrete, these cracks will
"reflect" through the tile - this is often
called "reflective cracking". Similarly, if
tile is installed over a control joint (The Tile Council of North America does not recommend this), movement in the
control joint will cause a crack in the tile. Even small
shrinkage cracks in concrete can be dimensionally active
where continued curing of the slab will cause these
cracks to expand or propagate - if this occurs, the
cracks will show through the tile.
This type of cracking can be easily avoided - either
by installing the tile on a mortar bed set over a cleavage
membrane (TCA Handbook detail F111 for example), or
by installing the tile over a crack isolation membrane
using a thinset method.
What is the difference in
a mortar bed and cleavage membrane installation and
a thinset installation using an anti-fracture membrane?
In the mortar bed installation, the mortar bed is not
bonded to the concrete - rather it is isolated from cracks
in the concrete by the cleavage membrane. This allows
the tile to "float" over the concrete.
In the thinset installation, a crack isolation/anti-fracture
membrane is bonded to the concrete. Tile is bonded (with
thinset) to the surface of the membrane. The internal
make-up of this membrane is such that movement in the
concrete is not directly transferred to the tile. The
membrane compensates where needed to prevent or reduce
force transference.
These membranes are either trowel applied or sheet
applied. In many cases multiple components or steps
are part of the system. Performance varies also - it
is important to check with the crack isolation manufacturer
regarding their installation instructions and intended
use.
If I use a crack
isolation/anti-fracture membrane can I eliminate the
expansion joints in the tile work?
It is a frequent misconception that anti-fracture
membranes allow you to eliminate expansion joints
- they do not. There always must be soft joints in the
tile work to allow for expansion and contraction. The
frequency of expansion
joints is recommended in the Tile Council of North America
Handbook.
Are there any other reasons
I might have cracked/loose/hollow tile?
There are many factors that can cause tile to lose its
bond to the subfloor. Losing bond to the subfloor has
the potential to lead to cracking in the tile layer:
1. Expansion and contraction, especially if movement
joints were not placed sufficiently in the tile layer
- note for outdoor, indoor but sunny, or moist installations,
this is especially important.
2. Poor quality thinset - especially where some shear
forces (from expansion and contraction or deflection)
are present
3. Paint or lacquer overspray on the subfloor
4. Sealer applied to the subfloor
5. Moisture induced deterioration of the subfloor
6. Delamination of the subfloor
7. Excessive deflection
8. Poor thinset coverage, thinset applied in "dabs",
thinset used beyond its pot life, or thinset that was
disturbed as it was curing.
9. Moisture sensitive adhesive (affected by hydrostatic
moisture or flooding)
Only an on-site inspection can truly evaluate the potential
reasons for cracked tile. Please visit the TCA
Team for information on these types of services.
If the floor sounds hollow
does it mean my tile will crack?
Occasionally, a floor will sound hollow even when the
tile is well bonded. This can occur when a mortar bed
method is used and the mortar has delaminated from the
supporting layer or when the subfloor itself is not sufficiently
thick or well attached. Other systems that intentionally
separate the tile layer from the substrate (such as the
mortar bed with a cleavage membrane system like TCA Handbook
detail F111) should be closely examined to ascertain if
hollow sounds necessarily imply that the tile is not bonded.
While a tile floor with hollow spots is not ideal,
it does not necessarily mean that floor failure is imminent.
On the contrary, over concrete if there is no deflection
in the floor; grout and gravity will help keep the floor
in place (as long as there are sufficient movement joints
in the tile and minimal shear forces). Over wood, floor
failure is more likely - movement in the subfloor could
cause grout to break away from the tile, compounding
the instability of the flooring.
Can I inject epoxy under the
tile to fix the hollow sound?
Some contractors have tried to inject epoxy to rebond
tile without reinstalling it - while this may work in
a small area, it is not practical over a large area. Further,
any repair that does not address the cause of the failure
may not last very long. |
