When do you use caulk
instead of grout?
Technically, anywhere there is a change in substrate
or backing surface such as the joint between walks
and floor and wall joint, caulk should be used in
place of grout since these surfaces move independently
of each other. However, it is important to recognize
and make the end user aware of some important points.
Often, installers use grout in place of caulk for
1) The caulk may not exactly
match the grout color
2) Even when the caulk exactly
matches the grout color when installed, it may not
match 6 months later (Caulk will "age"
differently from the grout.)
3) Caulk will need to be
maintained more often than grout
4) Mold may grow more easily
on caulk (except caulk treated with mildewcide)
than on grout
5) Acrylic caulks break down
in horizontal wet applications - silicone, urethane,
or multi-polymer caulks are better choices but can
be harder to
grout is used in place of caulk, the grout can cause
structural and aesthetic problems:
1) The grout will crack
allowing moisture to penetrate
2) Where the grout is sufficiently
strong, movement in the walls, floor, or countertop
can damage the tile
3) Grout cannot hide corner
cuts as well as caulk
caulk is the better choice - but the customer needs
to understand its limitations.
What is the difference between
epoxy grout and mortar and conventional grout and
We are often asked about epoxy grout and mortar
versus conventional grout and mortar.
Epoxy grout (meeting ANSI A118.3) is quite different
from cementitious grout and epoxy emulsion grout.
Made from epoxy resins and a filler powder, the
grout is extremely hard, durable, and nearly stain
proof. Often times the bond between tiles is stronger
than the tile itself.
You might wonder why this type of grout is not used
all the time. First, most installers find it harder
to use than cementitious grout. Also, it has a more
plastic appearance which, as with all matters of
aesthetics, some people like and some don't. Also,
it is much more difficult to shape and slope; this
can be done easily with cementitious grout and is
often needed to transition from one tile to another.
It may also slump in the joint hours after the floor
is finished because the grout becomes less viscous
initially as it heats up and cures. Lastly, it generally
takes days longer to cure and must be kept rigorously
clean. And it can cost 3 to 8 times as much as cementitious
There are even epoxy grouts on the market impregnated
with Teflon that are both stain proof (nearly) and
wipe clean incredibly easily.
It is also possible to smooth epoxy grout (with
or without Teflon) before it cures in a way that
leaves the surface with an extra slick plastic finish
to which it is very difficult for dirt to adhere.
These "100% solids" epoxy grouts should
not be confused with epoxy emulsion grouts which
are a mixture of cement and epoxy resins (ANSI A118.8).
Epoxy emulsion grouts are not stain proof and generally
will absorb liquids and stains. They are more similar
to polymer fortified cementitious grout (ANSI A118.7)
but may have better chemical resistance than some
polymer fortified grouts.
Epoxy thinsets offer greater bond strength and chemical
resistance than polymer modified cementitious thinset.
This performance comes at a price as epoxy thinset
is much more expensive than regular thinset. Typically,
they are only used to bond to difficult substrates
or where extraordinary chemical resistance is needed.
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Why is my grout and tile
There are many things that can cause excessive deflection
in your subfloor (and consequent cracking in the
tile) or you may have a perfectly sound subfloor
but not have prepared the floor properly for tile.
Here are a few of the most common questions:
1) Is the subfloor plywood
over joists 16" on center? If not, has the
installation system been designed to work with the
actual type of subfloor
2) What is the span of the
joists? - Are they suitably sized for the span to
achieve the L/360 deflection standard under the
expected live and dead
load? Are there any cracked, rotted, or termite
3) Was the subfloor screwed
to the joists - is there any possibility of movement
between the subfloor and the joists themselves?
4) Does the thinset used
match the conditions present (was a polymer additive
used and if so was it appropriate for the subfloor?)
5) Was the thinset coverage
satisfactory? What was the notch size of the trowel
6) Were expansion joints
used in the installation to allow for normal movement
7) Are any dimensionally
unstable or questionable materials also in the tile/subfloor/joist
sandwich? How about cushion vinyl, luaun, water-soluble
patching compounds or mortar materials.
8) Were all layers present
installed according to the applicable ANSI standards?
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What causes cracked or
There are several things that can cause cracked
grout and we would be guessing as to the cause.
It could be that a field inspection is needed to
determine why your grout is cracking.
Typically the most common causes are as follows:
1) Excessive deflection in
the substrate - this movement can cause the grout
to crack, and if sufficiently severe, can cause
tile to crack.
2) Grout that is insufficiently
packed into the joint. This most often occurs with
wall tile. If insufficient force is used while grouting
wall tile, it is
easy to "bridge" the joint where the grout
does not penetrate to the back of the joint. This
is especially true if sanded grout is used in joints
narrower than 1/8". The sand grains can easily
bridge a narrow joint - in this case the grout may
be only on the surface and have little
3) Grout made with an excessive
amount of water or polymer additive - the liquid
that goes into the grout ultimately must evaporate
that consumed by cement hydration). This evaporation
can cause pinholing in the grout and a weak grout
4) Grout packed after cement
hydration started. All cement based materials have
a pot life - if water is added to the mix after
the grout begins
curing in the bucket, the grout will be sufficiently
plastic to pack but will not cure into a hard homogeneous
block - rather it will be crumbly
Does your installer
have any idea as to the cause? The least likely
cause would be defective grout. Some other possible
things to look for:
a) Spacing of joists.
b) Type and size of floor
c) Span of floor joists.
d) Direction of the plywood
sheets and placement of gaps.
e) Were there gaps between
the sheets of plywood?
f) Type of adhesive and coverage
of that adhesive.
In some cases even the type of tile can affect this
(high or low water absorption tile bodies can vary
the methods and materials needed).
Therefore you can see this can be difficult to assess
without an on-site inspection. Usually minimum requirements
are 16" o.c. (on center) joists (2X10 or better
depending on span), 3/4-inch subfloor with 1/2"
underlayment (or backerboards made for tile). The
plywood sheets should be run with the long side
parallel to the joists (both layers). The top sheet
should be installed so that the joints don't fall
over the lower layer gaps nor above the joists.
The adhesive needs to coverage at least 80% in the
dry areas. The grout should be very dry and well
packed into the joints. The joints should not be
flooded with water when they are being cleaned.
Joints cannot be "grouted over" successfully.
At least 2/3 by depth of the old grout needs to
be removed when replacing or repairing grout.
Generally grout fails because of movement of the
substrate or improper mixing and installation of
grout. A ¾"-subfloor with 3/8"-underlayment
may not fail but it is marginal and could cause
problems. Stapling the two layers together could
be problematical. The best method is to screw and
glue the two sheets together. The underlayment should
be plywood designed for that purpose too not just
any plywood will do.
Our subsidiary consulting company, TCA-Team, LLC
is available for site consultations and failure
analysis on a fee basis should you desire an investigation.
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Repair & Removal of Grout
How do you remove grout
that is adhered to a tile floor?
Removing grout that is adhered to a tile floor can
be difficult. The type of tile greatly affects the
difficulty of grout removal; also, if the grout
was polymer modified, it may be more difficult to
In general, the more porous the surface, the better
grout will adhere - conversely, grout is more easily
removed from dense impervious tiles (e.g. porcelain).
To remove the grout, start with an alkaline cleaner
and a nylon scrub pad. Make sure to check that the
scrub pad is not damaging the tile. Normal floor
tile will not be affected by a using a scrub pad,
but some decorative tiles do not have the same surface
hardness. It is best to check your decorative in
a secluded area.
If the scrub pad is not effective, there are specialty
cleaners on the market that chemically attack the
grout. Typically these are weak acids. As with all
acids, follow the manufacturers warnings carefully
and use caution. Always check the tile in an inconspicuous
spot first in case the cleaner affects the tile.
Again, these specialty cleaners will not affect
most floor tiles - however, it is prudent to check.
Some tile installers use stronger acids that they
carefully dilute. While experienced professionals
can do this, there are great risks in doing so.
There is the possibility of bodily harm as well
as damage to the surroundings.
Can I paint over grout?
Changing grout color is more commonly done but again
the results are generally not as good as the original
item. The color in grout, unlike tile, comes from
liquid dispersed pigments. Obviously, these are
not fired but rather become part of the cement/sand
matrix. Grout is usually colored with an epoxy paint
made for the purpose and sold in tile shops. When
the grout is new, has not been sealed, and the edge
of the grout joint is neatly defined and when the
adjoining tile surface is very smooth, sometimes
good results can be achieved. However, if the grout
is not porous (from sealer or dirt), or the adjoining
tile is rough or absorptive, it may be impossible
to get a satisfactory result.
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Can I correct the color
of my grout?
When grout has been stained to the point that it
cannot be maintained or returned to its natural
color, you can return the grout back to near its
original color or any other color through the use
of a "grout stain". Some grout manufacturers
make grout colors, others will recommend specific
brands that they know work with their grout to correct
However, grout colorants work best with grout that
has not been sealed. Grout that has been sealed,
or has been washed with oil-based soaps (Pine Sol,
Murphy's Oil, etc.) can be very difficult to color.
Grout Stains are epoxy-based products that are specifically
designed to penetrate into the grout and seal the
surface with a permanent color. Once the grout has
been stained there is no need to seal it any further
with a penetrating/impregnating sealer.
Prior to staining, the grout joint should be cleaned
thoroughly to remove any dirt, oils, grease or sealers
with a professional strength Tile & Grout Cleaner.
This can be purchased from most Home Centers or
through your local Professional Floor Covering Dealer.
The edge of the tile also makes a difference in
the success of the colorant - tiles with well-delineated
edges are easier to treat than tiles with a large
bevel or textured edge. When the colorant is applied,
some will get on the tile - the easier it is to
remove from the tile (and the better it sticks to
the grout), determines in part how good the finished
Also, you will want to try a test area since grout
treated with a colorant does not look the same as
originally colored grout. On the plus side, grout
colorants also seal the grout and protect it with
an "epoxy-like" finish. Typically, grout
that has been treated with a colorant does not need
to be sealed.
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How do I clean grout?
Cementitious grout, as you may have observed, is
porous - it can absorb a stain. Looked at under
a microscope, there is a large surface area to absorb
stains. For this reason, many owners choose to seal
their grout … usually the better the sealer,
the more the grout joint is protected. Even better,
if epoxy grout is used, it is virtually as stain
proof as the tile.
Removing stains from cementitious grout is similar
to removing stains from clothing. The same cleaners
you might use on clothes to get out a stain should
also work on grout.
Keep in mind though, that grout is based primarily
of cement and sand. Sand, like glass, is unaffected
chemically by most cleaners. Cement is not; rather
it is alkaline based and is dissolved by acids.
As baking soda and vinegar react, so do grout and
Accordingly, it is better to clean grout with an
alkaline cleaner (Spic and Span, Mr. Clean, etc.)
than an acid based cleaner. There are also specialty
cleaners available at most tile retailers that are
designed for tile and grout. There are also cleaners
with enzymes that attack stains similar to enzyme
pre-soaks for laundry.
The same cleaner that works on the grout generally
will work well on the tile. In fact, since the tile
is usually so easy to clean, the tile can often
be cleaned with water.
Just a few more important points: As the grout can
absorb the soap as well as a stain - do not clean
with oil or wax based cleaners - Murphy's Oil soap,
Pine Sol, etc. These products will leave a waxy
or oily film in the grout… And, even good
alkaline cleaners if not properly rinsed, will leave
a sticky soap film. This usually attracts dirt.
In fact, truly clean ceramic tile without any sticky
soap film will stay very clean as tile does not
tend to hold an electrostatic charge (which can
attract some kinds of dirt).
The absolutely best way to clean grout is to apply
the cleaner and then vacuum ("shop vac")
up the dirty water. This lifts the dirt off the
joint. Apply rinse water and vacuum that water up.
This lifts off any remaining soap film.
Just to mention it, there are tile installers that
remove very stubborn stains on grout with an acid
(like straight vinegar or a stronger acid). There
they have elected to dissolve the top layer of grout
molecules so the stain is no longer attached to
anything. While this works, it is not recommended
by the grout manufacturers - needing to regrout
is sometimes the result. Also, extreme care should
be used when handling any acids.
Should you be unable to get your grout clean through
conventional methods, you may also want to try steam.
Some stains that do not respond to conventional
cleaners will come clean when subjected to pressurized
steam. As a last resort, some installers elect to
cut out the grout and regrout. This is possible
although care must be taken to not damage or loosen
the tile. Generally it is not possible to grout
directly over the old grout without cutting the
old grout out. The same contaminants that made the
old grout dirty may prevent new grout from sticking
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How can I prevent my grout
To prevent staining in the future, you should seal
Generally, sealer is a very good idea for cementitious
grout (regular grout - not epoxy grout). For glazed
floor tile it is not a good idea to spray anything
on the tile - the glaze of the tile will be easier
to clean and longer lasting than any coating. For
unglazed tile, generally sealers are recommended
although it is important to follow the recommendations
of the tile manufacturer.
For cementitious grout, there are two broad classes
of sealer: Penetrating sealer that chemically bonds
with the grout and repels water (and water based
stains) and topical sealers that coat the surface
of the grout and repel almost everything (until
they are worn off by foot traffic).
Each type of sealer has its advantages and disadvantages.
Additionally there are hybrids on the market combining
In general the topical sealers are less expensive
but give the grout a plastic appearance. Also they
are subject to wear and tear and very sensitive
to water in the grout while curing. As stated above,
the plastic coating does block almost everything…until
it is compromised by foot traffic.
The penetrating sealers are more expensive but also
more durable. There are also penetrating sealers
that repel oil based stains that are even more expensive.
They can be applied on the grout sooner than the
topical sealers, as they are usually vapor permeable.
As they do not coat the grout (but penetrate in),
they do not change the large microscopic surface
area. While stains don't penetrate, they can be
a little harder to remove (just a little) because
the sanded texture of the grout hasn't been changed.
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, or by installing the tile over
a crack isolation membrane using a thinset method.
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What is the difference
in a mortar bed and cleavage membrane installation
and a thinset installation using an anti-fracture
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.
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
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)
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 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
Porcelain vs Non-Porcelain Tiles
What are the differences
between porcelain tiles and non-porcelain tiles?
Porcelain tiles are typically made with "porcelain"
clays that have specific properties. Typically,
these tiles are dense and by definition, they have
water absorption of 0.5% or less. Non-porcelain
tiles have water absorption greater than 0.5%.
Because porcelain tiles have a low water absorption,
they are usually frost resistant - although, not
always. To know if a tile is frost resistant, you
should check the manufacturer's literature.
There are also many non-porcelain tiles that can
be used in freeze thaw environments and that are
manufactured with properties similar to porcelain
There are both glazed and unglazed porcelain tiles
- it is important to know the difference, as the
glazed variety is usually a little easier to clean.
Typically, glazed porcelain tiles have filled in
microscopic holes that could be present in the unglazed
tile. On the other hand, unglazed porcelains may
have better slip resistance.
Non-porcelain tiles cover a wide range of properties
- typically they are glazed (although unglazed quarry
tile is the exception) and the glaze layer can be
extremely durable. However, as there are differences
from one glaze to another, it is important to check
if the tile has been tested and to make sure the
glaze hardness is suitable for your application.
In general, non-porcelain tiles are easier to bond
to the floor and usually easier to cut. Porcelain
tiles are harder to bond and harder to cut. While
this can be relevant to the tile installer, it generally
makes little difference to the end-user, so long
as the installer uses the right materials.
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What is a through-body
Some people refer to unglazed porcelain tile as
"through body" - i.e. the color on the
top goes all the way through. Even in extreme applications,
these tiles tend not to show wear as the porcelain
is quite durable (harder than granite) and the color
goes all the way through.
Many glazed porcelains also have extremely good
durability. Although the color in the glaze layer
may be different from the body, the surface is usually
sufficiently resistant to abrasion to not show wear
in typical applications.
How is glaze resistance
to abrasion determined?
Since 1999, U.S. and European manufacturers
have been using the same testing method for determining
glaze wear resistance - with a value of 4 (on a
scale from 0 to 5) being good for almost all applications
except the most abrasive and dirty environments.
However, lower ratings are also fine depending on
where the tile will be used and how much traffic
and outside dirt (especially sand, because it is
abrasive) will be present.
A rating of 4 can be achieved if there is no visible
wear (under test conditions) after 2100, 6000 or
12000 revolutions of the test equipment. A value
of three can be achieved by passing 750 or 1500
revolutions. Usually the product specifications
will indicate which value was passed when the testing
was done (for example, one tile might be rated Class
3, passing 1500 revolutions, another tile could
be Class 3, passing.
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