Usage Guide

Proper Bedding Area: Natural stones are more vulnerable to cracking as a result of voids in the
setting bed than most ceramic products. Back-buttering of the stone tile is essential, and the
minimum acceptable bedding area is 95% contact with no voids exceeding 2 in² and no voids within
2” of tile corners on 3/8” tile. The minimum acceptable bedding area is 80% contact with no voids
exceeding 4 in² and no voids within 2” of tile corners on ¾” or thicker material. All corners and edges
of stone tiles must always be fully supported and contact shall always be a minimum of 95% in
water-susceptible conditions.
Grout Dye Staining: The use of dyes in grouts should always be tested to verify that the dyes will
not leach into the stone, causing a “picture frame” stain. This is most common when using grouts
of contrasting color, although grouts dyed with matching color to the stone have been known to
cause staining in some instances.
Acid Sensitivity: The use of natural stones in environments where acid exposure is likely requires
a proper stone selection to avoid attack to the stone. Most notably, the calcium carbonate and
calcite based stones will react to relatively mild acids, such as lemon juice, vinegar, and sliced
tomatoes. The result is not a stain, which could be removed, but an etching of the stone surface,
which cannot be removed without refinishing the stone. In polished finish stones, a mild acid attack
will usually manifest itself as a “dull” spot within the surrounding glossy surface.
Delamination: Many stone varieties have pronounced bedding planes, along which a predetermined
“rift” exists. “Rift” is defined simply as the direction along which a stone is most easily split. Bedding
planes can be a region of weakness, and some stones, particularly sandstones and some slates, will
actually delaminate along inter-bedding plane boundaries after installation. This will result in a
portion of the stone thickness separating and dislodging itself from the rest of the stone, and is not
related to any failure in adhesive, since the bonded portion of the stone remains in place. Research
is required to verify the adequacy of the stone material for the intended application. Differential
mineral expansion due to weathering and thermal cycles tend to accelerate this occurrence, and
freeze/thaw cycling is obviously an additional factor.
Lot Specific Issues: Being products of nature, stones are subject to the variability of any product
harvested from nature. Some stone deposits are remarkably uniform through hundreds of feet of
depth times vast lateral distances. There are cases of replacement pieces having been quarried
to repair or extend building decades old, and the replacements matched the existing nearly
seamlessly. In contradiction to these examples, there are quarries where the inter-block, and even
intra-block variability are so great that a given lot of material cannot be matched one month later.
In such cases, extreme care is necessary to ensure that adequate quantities are ordered, including
requirements for waste, breakage, and attic stock.
Lippage vs Grinding in Place: Lippage in stone tile flooring is accentuated from what would be
perceived in a ceramic tile flooring for several reasons. Natural stones tend to be installed with
tighter joints, they typically have extremely slight, or no chamfer at their edges, and many natural
stones are provided in a very high gloss, polished surface finish. Industry standards limit lippage
between adjacent units of smooth finished natural stone flooring to 1/32”, which is approximately
the thickness of a standard, plastic credit card. When this is not achieved, there is the option
of grinding the stone tiles in place to eliminate the lippage. This work is to be done by skilled,
experienced technicians, as care must be taken to avoid a “wavy” looking finished floor. In some
cases, installing contractors will plan to grind the finished floor regardless of the lippage amount,
usually per the requirement of the client. Lippage should still be minimized to the extent possible
during installation to avoid extremely thin stone sections after grinding.
Requirement for Pre-soaking: Installing high porosity stones in hot, dry climates often requires
that the stone be pre-soaked prior to installation. Failure to do so can result in the stone wicking
excessive amounts of water out of the setting bed, leaving the bed with inadequate water to
accomplish proper hydration of the cements.
Translucence: May occur in some white or very lightly colored marbles and onyxes having a crystal
structure that will transmit light to varying degrees depending upon stone thickness and finish.
Translucence can be an aesthetically intriguing decorative attribute.
Mixing Types of Materials: Designs calling for a mixture of stones with different physical properties,
while aesthetically interesting, can give rise to problems of wear and of maintenance, mainly on
floor areas. Re-polishing will pose problems, should that need arise. The Specifier should be aware
that mixing types of stones means there will be different abrasion resistance levels as well as
different densities of stones that must be considered in the long term maintenance of the stone
and its wearability.
Yellowing: A stone may turn yellow due to dirt or soap scum set in it. Waxes and other types of
coatings can also yellow with age. Certain stones will naturally yellow with age as a result of
oxidation of the iron within the stone. This is especially true with white marbles.
Rusting: Some stones, and specifically slates, contain deposits of minerals that can react to
moisture. Stone bleeding or rusting is a common example of this. Caution should be used in
installations where slate would be exposed to standing, run off water or too much humidity. As
water works its way through the stone, if the stone contains iron oxide, some of it may liquefy. This
iron will eventually surface through the stone and deposit itself on the surface of the stone. The
rust will return over time and may have to be cleaned periodically.
MOST COMMON STONE FINISHES:
Polished: Mirror gloss, with sharp reflections.
Honed: Dull sheen, without reflections, achieved by abrasive heads. The degree of honing depends
on the stone, but may vary from light to heavy. Generally, it is recommended that a natural stone
floor receive a honed rather than a highly polished finish in commercial applications. Etching,
scratching, and traffic paths will be far less obvious on a honed surface, thus making for easier
maintenance.
Flamed or Thermal: Plane surface with flame finish applied at high temperature by mechanically
controlled means to ensure uniformity; changes the color of the stone.
Water-jet Finish: Gives a more uniform, textured finish and allows more of the natural color to
show.
Sandblasted: Coarse plane surface produced by blasting an abrasive, allowing a fine-textured
finish; may lighten the color.
Bush-hammered: Coarsely textured surface produced by hammering, and may vary according to the
metallic head used, from fine point to very coarse, and may leave high, lighter-colored markings.
Natural Cleft: A cleavage face formed when the stone is split into any thickness.
Tumbled: Method of putting tiles in a mixing container with sand and rotating them, allowing the
edges and corners of the tiles to chip. This method is used to give an antique and old look.
Brushed: This finish is created by using specific brushes to give the stone a softer, aged look. When
stones are brushed, micro-veins open up. With traffic, brushed stones will increase their patina
naturally and more veins may open up.
Gauged: Done by a machine, usually with circular abrasives to grind the material to a specific
thickness.
NATURAL STONE CARE AND MAINTENANCE GUIDE CONTINUED
DALTILE.COM
Page 21 of 23
IMAGINE WHAT’S POSSIBLE
™