1 Scope
NOTE This standard governs the materials and installation of natural dimension-stone tile and thin slabs — granite, marble, limestone, travertine, slate, quartzite, sandstone, and the serpentine stones commonly sold as "green marble" — set by the thin-bed, medium-bed, and thick-bed (full mortar-bed) methods on interior and protected exterior floors, walls, wainscots, stair treads, risers, thresholds, base, and countertops. (1.1)
1.2The Contractor shall treat the installation as a coordinated system.
1.3The Contractor shall select a method from the TCNA Handbook for Ceramic, Glass, and Stone Tile Installation and the Natural Stone Institute Dimension Stone Design Manual appropriate to the stone, substrate, and service.
1.4The Contractor shall verify that the stone, setting material, membrane, and grout are mutually compatible and approved for the specific stone.
1.5The Contractor shall not begin setting stone until the substrate has passed the flatness, soundness, and moisture acceptance criteria of this standard.
1.6The Contractor shall coordinate the concrete substrate, its surface finish, its curing, and the location of structural and control joints with the structural and concrete work, so that every structural, cold, and control joint in the substrate and every change in substrate plane or material is carried through the stone as a movement joint.
1.7The Contractor shall coordinate waterproofing of the building envelope and of wet areas with Below Grade Waterproofing where stone is applied over a waterproofed assembly. NOTE Natural stone is specified where the depth, movement, and individuality of a natural material are wanted, and because every piece is a sample of a geologic deposit whose color, vein, shade, density, porosity, and strength vary from piece to piece, the correct stone type, its governing ASTM material specification, and the service environment are the most important things to identify. (1.9)
NOTE A stone installation is a layered system whose durability is governed far more by the substrate, setting bed, membrane, and movement-joint design than by the stone itself, and the majority of field failures originate in substrate movement, wrong setting material, omitted movement joints, or unaccounted-for moisture rather than in a defect of the stone. (1.10)
2 Referenced Standards
NOTE The following standards are referenced in this document. (2.1)
| Standard |
Title |
| ASTM C503 / C503M |
Specification for Marble Dimension Stone |
| ASTM C568 / C568M |
Specification for Limestone Dimension Stone |
| ASTM C615 / C615M |
Specification for Granite Dimension Stone |
| ASTM C616 / C616M |
Specification for Quartz-Based (Sandstone) Dimension Stone |
| ASTM C629 / C629M |
Specification for Slate Dimension Stone |
| ASTM C1526 |
Specification for Serpentine Dimension Stone |
| ASTM C1527 / C1527M |
Specification for Travertine Dimension Stone |
| ASTM C97 / C97M |
Test Methods for Absorption and Bulk Specific Gravity of Dimension Stone |
| ASTM C99 / C99M |
Test Method for Modulus of Rupture of Dimension Stone |
| ASTM C170 / C170M |
Test Method for Compressive Strength of Dimension Stone |
| ASTM C880 / C880M |
Test Method for Flexural Strength of Dimension Stone |
| ASTM C241 / C241M |
Test Method for Abrasion Resistance of Stone Subjected to Foot Traffic |
| ASTM C1353 / C1353M |
Test Method for Abrasion Resistance of Dimension Stone Subjected to Foot Traffic Using a Rotary Platform Abraser |
| ASTM C1028 |
Test Method for Static Coefficient of Friction (superseded by ANSI A326.3 for slip resistance) |
| ANSI A137.1 |
Specifications for Ceramic Tile (referenced for tile-form stone dimensional and DCOF requirements) |
| ANSI A108.01 / A108.02 |
General Requirements and Materials, Environmental, and Workmanship for Installation of Tile |
| ANSI A108.5 |
Installation with Dry-Set or Latex-Portland Cement Mortar |
| ANSI A108.6 |
Installation with Chemical-Resistant, Water-Cleanable Tile-Setting and -Grouting Epoxy |
| ANSI A108.13 |
Installation of Load-Bearing, Bonded, Waterproof Membranes for Thin-Set Ceramic Tile and Dimension Stone |
| ANSI A108.17 |
Installation of Crack-Isolation Membranes for Thin-Set Ceramic Tile and Dimension Stone |
| ANSI A118.1 |
Dry-Set Portland Cement Mortar |
| ANSI A118.3 |
Chemical-Resistant, Water-Cleanable Tile-Setting and -Grouting Epoxy |
| ANSI A118.4 |
Modified Dry-Set Cement Mortar |
| ANSI A118.5 |
Chemical-Resistant Furan Mortars and Grouts |
| ANSI A118.6 |
Standard Cement Grouts |
| ANSI A118.7 |
High-Performance Cement Grouts |
| ANSI A118.10 |
Load-Bearing, Bonded, Waterproof Membranes for Thin-Set Installation |
| ANSI A118.12 |
Crack-Isolation Membranes for Thin-Set Installation |
| ANSI A118.15 |
Improved Modified Dry-Set Cement Mortar |
| ANSI A326.3 |
Test Method for Measuring Dynamic Coefficient of Friction of Hard-Surface Flooring Materials |
| TCNA Handbook |
TCNA Handbook for Ceramic, Glass, and Stone Tile Installation (method designations and movement-joint guideline EJ171) |
| NSI Dimension Stone Design Manual |
Natural Stone Institute Dimension Stone Design Manual |
| IBC |
International Building Code (current edition adopted by jurisdiction) |
2.2All materials, testing, and installation shall comply with the latest edition adopted by the Authority Having Jurisdiction for each of the standards listed above.
2.3Where the contract documents, a referenced standard, the TCNA Handbook method called out, the Natural Stone Institute Dimension Stone Design Manual, or the stone or setting-material manufacturer's or fabricator's written instructions impose a more stringent requirement than the minimum of any other standard, the more stringent requirement governs unless the Architect of Record directs otherwise in writing.
NOTE For natural stone the fabricator's and setting-material manufacturer's written instructions for the specific stone are not merely advisory, because a moisture-sensitive or friable stone has handling, setting, and sealing requirements the generic standards do not capture, and disregarding them voids the installation warranty. (2.4)
NOTE The ASTM dimension-stone material specifications (C503, C568, C615, C616, C629, C1526, C1527) are the foundation of this standard, each defining for its stone type the minimum physical properties — absorption per ASTM C97, density, compressive strength per ASTM C170, modulus of rupture per ASTM C99 and flexural strength per ASTM C880, and abrasion resistance per ASTM C1353 — that a sound, durable stone must meet. (2.5)
NOTE The TCNA Handbook supplies the tested installation methods by designation and the movement-joint guideline EJ171, the NSI Dimension Stone Design Manual is the recognized source for stone-specific selection and tolerance guidance, and where stone is supplied in tile form the dimensional and slip-resistance provisions of ANSI A137.1 and ANSI A326.3 also apply. (2.6)
3 Submittals
3.1 Action Submittals
3.1.1The Contractor shall submit the following for the Architect's review prior to procurement and installation:
- Stone material certification reporting, for each stone, the commercial and geologic name, the quarry source, the governing ASTM specification, and the measured physical properties (absorption and density per ASTM C97, compressive strength per ASTM C170, flexural strength per ASTM C880 or modulus of rupture per ASTM C99, and abrasion resistance per ASTM C1353 for floor stone), demonstrating compliance with the governing specification
- Product data for each setting material, membrane, grout, and accessory, identifying the governing ANSI specification and a written statement that the selected setting material, membrane, and grout are approved by their manufacturer for the specific stone and substrate and for the service condition, including an explicit statement of suitability for moisture-sensitive or translucent stone where such stone is specified
- The TCNA Handbook method designation, or the NSI Dimension Stone Design Manual detail, proposed for each stone location, identifying the substrate, membrane, setting bed, and movement-joint treatment
- Full-range samples and, for stone with significant directional vein or shade variation, full-size sample sets or a reviewed approved range establishing the acceptable extremes of color, vein, shade, and finish
- Slip-resistance (DCOF) test data per ANSI A326.3 for each floor stone in its specified finish, identifying the use classification for which the value qualifies the stone
- Shop drawings showing stone layout, setting-out and control lines, vein direction and match (book-match, slip-match, blend), the location of every movement and perimeter joint, edge and trim profiles, stair and threshold details, and slab jointing, coordinated with the finish plans, elevations, stone layout, and details
- For slabs on or below grade and for moisture-sensitive stone, the substrate moisture test result and the basis for the membrane and setting-material selection
- Sealer and impregnator product data with the stone manufacturer's or fabricator's confirmation of compatibility, and a statement of whether a pre-installation impregnating sealer is required
☐ Stone material certification — name, source, ASTM spec, and measured physical properties (C97, C170, C880/C99, C1353)
☐ Product data — setting materials, membranes, grout (ANSI designation + stone-specific compatibility statement)
☐ TCNA method / NSI detail per location
☐ Samples — full color/vein/shade range and approved range set
☐ DCOF slip-resistance data per ANSI A326.3 (floor stone, specified finish)
☐ Shop drawings — layout, vein match, movement joints, edge profiles, stair/threshold details
☐ Substrate moisture test result (slabs on/below grade and moisture-sensitive stone)
☐ Sealer/impregnator product data with compatibility confirmation
3.1.2Installation shall not begin until the stone material certification, the setting-material compatibility statement, and, where applicable, the substrate moisture report have been submitted and reviewed.
NOTE The stone type and substrate condition together determine the setting material, the membrane, the sealing requirement, and the freeze-thaw suitability. (3.1.3)
3.2 Closeout Submittals
3.2.1The Contractor shall submit the following closeout documentation:
- Manufacturer warranty documentation for the stone, setting materials, and sealer, executed in the Owner's name where an owner-registered warranty is offered
- Maintenance instructions describing permitted cleaning agents, the resealing interval and product, and prohibited cleaners (acidic cleaners on calcareous stone, abrasive pads on polished finishes) for each stone and finish
- Attic-stock transmittal documenting the quantity, stone, finish, size, and block/lot of spare stone delivered to the Owner
☐ Manufacturer warranty documentation for stone, setting materials, and sealer (executed in Owner's name where offered)
☐ Maintenance instructions (permitted cleaning agents, resealing interval and product, prohibited cleaners)
☐ Attic-stock transmittal (quantity, stone, finish, size, block/lot of spare stone)
4 Quality Assurance
4.1 Installer Qualifications
○ Credentialed stone / large-format installer required (slabs, polished, moisture-sensitive, or any edge over 15 in)
○ Experienced commercial natural-stone installer
○ Experienced commercial tile installer (calibrated stone tile, interior dry only)
4.1.1Stone shall be installed by an installer with documented experience in commercial natural-stone installations of the specific stone type, finish, and method required.
4.1.2The Contractor should employ installers credentialed under a recognized industry program for stone and large-format work.
4.1.3The Contractor shall not assign stone work — particularly moisture-sensitive, friable, polished, or large-slab stone — to labor experienced only in manufactured tile.
NOTE Stone work demands skills that ordinary tile work does not, including matching vein and shade across a wall, setting moisture-sensitive stone with epoxy, controlling lippage on large gauged slabs, dry-laying and blending from multiple crates, and finishing field-cut edges to match factory edges. (4.1.4)
4.2 Mock-Up
○ Yes — representative area of each stone, including a movement joint, an edge/trim condition, and a wet-area or stair detail where applicable
○ No
4.2.1Where a mock-up is required, the Contractor shall install a representative area of each stone type and finish at a location directed by the Architect, including at least one movement or perimeter joint, one edge or trim condition, one internal or external corner, one transition to an adjacent finish, and a stair, threshold, or wet-area detail where such conditions occur.
4.2.2The mock-up shall remain available for comparison throughout the work.
NOTE For stone the mock-up establishes the accepted standard for the natural range of color, vein, and shade, the joint width and grout color, the lippage, the finish, and the sealer appearance, and because natural variation is intrinsic the approved range, not a single sample, defines acceptance. (4.2.3)
4.3 Lippage and Joint Acceptance
○ 1/32 in plus inherent warpage (joints under 1/4 in; gauged/calibrated stone)
○ 1/16 in plus inherent warpage (joints 1/4 in and wider)
○ Per ANSI A108 / NSI for the joint width, stone, and finish
4.3.1Lippage — the difference in elevation between the edges of two adjacent units — shall not exceed the allowance of ANSI A108 and the NSI Dimension Stone Design Manual for the joint width, stone, and finish, plus any inherent warpage permitted for the stone.
4.3.2The grout-joint width shall not be less than the minimum the stone's dimensional and thickness variation warrants.
NOTE Lippage is more conspicuous on stone than on tile because polished and honed stone reflects light across the joint and cleft and calibrated stone vary in thickness, and it becomes harder to control as unit size increases and joint width decreases, which is why large slabs demand a flatter substrate and a controlled minimum joint. (4.3.3)
4.4 Pre-Installation Conference
4.4.1Before installation begins, the Contractor shall hold a pre-installation conference with the Architect, the stone fabricator, and the installer to review the stone type and its moisture sensitivity and friability, the substrate condition, flatness, and moisture, the TCNA method or NSI detail and the setting materials selected, the layout, vein-match, and blending plan, the movement-joint plan, the sealing requirement and sequence, and the environmental conditions in the space.
NOTE Most stone disputes trace to a property of the stone or a condition of the substrate that was known but not acted upon before setting, and the conference exists to surface and resolve those conditions before any stone is set. (4.4.2)
5 Environmental and Service Conditions
5.1 Service Environment Classification
NOTE The service environment determines the stone type and finish, the freeze-thaw suitability, the slip-resistance requirement, the membrane requirement, the setting and grouting materials, and the sealing regimen. (5.1.1)
Interior dry — floors and walls not regularly wetted
Interior wet — restrooms, showers, food service, fountains
Interior heavy-duty — high-traffic lobbies, retail, transit floors
Exterior, freeze-thaw exposed — protected exterior floors, walls, and paving
Submerged / continuous-wet — pools, fountains, water features
5.1.2The service environment shall be established for each stone location before materials are selected.
5.1.3Calcareous stone in freeze-thaw exterior service shall be used only where the specific stone has demonstrated freeze-thaw durability.
5.1.4The Contractor shall confirm the service classification for each location from the contract documents before selecting materials.
NOTE Interior dry applications tolerate the broadest range of stone and finishes, while interior wet applications require a waterproof assembly, slip-resistant floor stone, an appropriate setting material, and attention to efflorescence and staining in absorptive stone. (5.1.5)
NOTE Exterior and freeze-thaw applications require a dense, low-absorption stone because an absorptive stone — most limestone, most marble, many travertines and slates — will spall, delaminate, or deteriorate when absorbed water freezes, and submerged or continuous-wet service requires a non-staining low-absorption stone, an epoxy or non-efflorescing setting system, and engineering beyond this standard. (5.1.6)
5.2 Temperature During Installation and Cure
5.2.1The installation area and the substrate shall be maintained at a minimum of 50 °F (10 °C) and a maximum of 100 °F (38 °C) during installation and for the cure period required by the setting and grouting materials, typically not less than 7 days for cementitious materials before exposure to water or traffic.
NOTE Cementitious mortars and grouts gain strength through hydration, which slows or stops below approximately 50 °F and which can flash-set or shrink-crack in excessive heat, epoxy materials have a still narrower temperature window, and stone set or grouted outside the window or trafficked before cure debonds or cracks at the bond line. (5.2.2)
5.3 Substrate Moisture
○ Bonded waterproof membrane (ANSI A118.10) over slab — wet areas, moisture-sensitive or absorptive stone
○ Vapor-managing / moisture-tolerant assembly with cementitious setting bed — durable non-sensitive stone only
○ Standard thin-set over sound dry slab — interior dry, above-grade, durable stone only
5.3.1Where stone is installed over concrete slabs on or below grade, the substrate moisture condition shall be evaluated and a bonded waterproof or vapor-managing membrane provided where moisture would otherwise drive efflorescence, staining, debonding, or warping through the assembly.
5.3.2Where the assembly includes moisture-sensitive stone or a moisture-sensitive membrane or adhesive, the substrate moisture shall be measured (the relative-humidity method of ASTM F2170 being the recognized measure) and the membrane and setting materials selected for the measured condition.
NOTE Natural stone is far more vulnerable to substrate moisture than manufactured tile, because residual slab moisture and alkalinity carry mineral salts that deposit as efflorescence on and within absorptive stone, stain light and translucent stone, and in moisture-sensitive stone supply the water that causes warping and bond loss. (5.3.3)
5.4 Lighting for Inspection
5.4.1Permanent or equivalent temporary lighting shall be operating during installation and inspection so that lippage, shade and vein match, joint alignment, hollow-bonded areas, finish uniformity, and surface defects can be evaluated under realistic conditions.
5.4.2The finished work shall be evaluated under the lighting in which it will be viewed in service, except that critical-light conditions called out in the contract documents shall be evaluated under raking light if specified.
NOTE Polished and honed stone is highly sensitive to raking light, which exaggerates lippage and finish variation. (5.4.3)
6 Stone Products
6.1 Stone Type and Governing Specification
NOTE The stone type and its governing ASTM specification determine the service environment, the freeze-thaw suitability, the strength, the absorption and staining behavior, the moisture sensitivity, the appropriate finishes, and the maintenance regimen. (6.1.1)
Granite (ASTM C615) — dense igneous; floors, exterior, high-traffic, wet
Marble (ASTM C503) — calcareous metamorphic; interior floors and walls
Limestone (ASTM C568) — calcareous sedimentary; interior, protected exterior
Travertine (ASTM C1527) — porous calcareous; interior floors and walls (filled/unfilled)
Slate (ASTM C629) — fissile metamorphic; floors, treads, exterior paving
Quartzite / quartz-based sandstone (ASTM C616) — siliceous; durable floors and exterior
Serpentine 'green marble' (ASTM C1526) — moisture-sensitive; interior, epoxy-set
6.1.2The stone type shall be selected for the use, traffic, exposure, and maintenance expectations of each space, shall be identified by both commercial and geologic name and quarry source, and shall be indicated in the stone schedule. 6.1.3Each stone shall comply with its governing ASTM dimension-stone specification (C503, C568, C615, C616, C629, C1526, or C1527) and shall be certified by measured physical properties.
6.1.4Stone used in exterior, freeze-thaw, or submerged service shall be a dense, low-absorption stone demonstrated to be durable in that service.
6.1.5Calcareous stone shall not be used in freeze-thaw exterior service unless the specific stone is documented as freeze-thaw durable.
NOTE Granite (ASTM C615) is a dense igneous stone of very low absorption (typically not more than about 0.40 percent) and high strength, the most durable common stone and the default for high-traffic, wet, and exterior freeze-thaw floors, while marble (ASTM C503) is a calcareous metamorphic interior stone, soft and acid-sensitive, etched by acids and unsuitable in most cases for exterior freeze-thaw service. (6.1.6)
NOTE Limestone (ASTM C568) is a calcareous sedimentary stone classified by density into three types whose use is governed by the class, travertine (ASTM C1527) is a porous calcareous stone with natural voids that may be filled or unfilled, slate (ASTM C629) is a fissile cleft stone whose absorption and iron content require attention to staining, quartz-based sandstone and quartzite (ASTM C616) are durable siliceous stones, and serpentine "green marble" (ASTM C1526) is the archetypal moisture-sensitive stone. (6.1.7)
6.2 Limestone Density Classification
○ Type I — low density (interior, light service)
○ Type II — medium density (interior floors and walls, general)
○ Type III — high density (high-traffic floors, protected exterior)
○ Not applicable — stone is not limestone
6.2.1Where limestone is specified, the density class of ASTM C568 shall be selected for the service.
NOTE Because absorption, density, compressive strength, and modulus of rupture all rise with the class, a low-density Type I limestone suited to a protected interior wall will absorb, stain, and wear unacceptably as a high-traffic floor where a high-density Type III is required, so selecting limestone without specifying the class invites the wrong stone. (6.2.2)
6.3 Physical Properties
Ha 10 — light residential / very light commercial
Ha 12 — moderate commercial floor traffic
Ha 15 — heavy commercial / institutional floor traffic
Per governing ASTM specification for the stone
6.3.1Each floor stone, and each stone in structural or exterior service, shall meet the minimum physical properties of its governing ASTM specification for absorption, density, compressive strength, flexural strength or modulus of rupture, and (for floors) abrasion resistance, verified by the test methods cited and reported in the stone certification.
6.3.2Water absorption shall be determined per ASTM C97 and shall not exceed the maximum of the governing specification for the stone and class.
6.3.3Low absorption shall be confirmed for any stone in wet or freeze-thaw service.
6.3.4Compressive strength shall be determined per ASTM C170 and flexural strength per ASTM C880 (or modulus of rupture per ASTM C99), each meeting the minimum of the governing specification.
6.3.5Abrasion resistance of floor stone shall be determined per ASTM C1353 and the abrasion hardness shall be appropriate to the traffic (light, moderate, or heavy commercial).
NOTE These properties are not interchangeable between stones nor assumable from the commercial name, because two stones sold as "marble" or "quartzite" can differ by an order of magnitude in absorption and strength, and only the measured values against the governing specification establish suitability. (6.3.6)
NOTE The stone form and thickness determine the setting method, the substrate flatness requirement, the handling, and the joint and lippage control. (6.4.1)
Gauged / calibrated stone tile — uniform thickness, thin-bed set
Cleft-finish tile (slate, quartzite) — variable thickness
Cut-to-size dimension stone — fabricator-cut to plan
Thin slab — large-format gauged slab
As scheduled
0.3750.75
0.3750.50.6250.75
Default: 0.375 in
6.4.2The stone thickness shall be coordinated with the stone strength, the span and support, and the anticipated load, and indicated in the stone schedule and details. NOTE Gauged calibrated stone tile of uniform thickness is set by the thin-bed method, cleft-finish stone such as slate varies in thickness and is set by a medium-bed or full mortar-bed method that accommodates the variation, and floor stone thinner than the stone's strength warrants will crack over any support gap. (6.4.3)
6.5 Surface Finish
NOTE The finish affects appearance, slip resistance, cleanability, maintenance, and durability. (6.5.1)
Polished — high gloss (interior walls, low-traffic floors, countertops)
Honed — smooth matte (interior floors and walls, general)
Flamed (thermal) — coarse slip-resistant (granite floors, exterior)
Brushed / antiqued — textured low-sheen
Sandblasted — uniform matte texture
Cleft (natural split) — slate and quartzite
Tumbled — softened edges and surface
6.5.2The finish shall be selected for the stone, the service, and the slip-resistance requirement, and shall be consistent with the approved mock-up.
6.5.3Polished finishes shall not be used on wet floors or sloped surfaces where the slip-resistance requirement cannot be met.
NOTE A polished finish maximizes color and reflectivity but minimizes slip resistance and is best reserved for walls, countertops, and low-traffic feature floors, a honed finish is the general-purpose floor and wall finish, flamed and brushed finishes are the standard for granite floors and exterior paving, and cleft finishes occur naturally on slate and some quartzite. (6.5.4)
6.6 Slip Resistance
0.420.6
0.420.50.6
Default: 0.42 DCOF
6.6.1The dynamic coefficient of friction of floor stone in its specified finish shall be measured per ANSI A326.3 and shall meet the minimum for the applicable use classification.
6.6.2Ramps, shower floors, pool decks, entries subject to tracked-in water, and stair treads require classification-specific values and a textured finish and shall not be defaulted to the level-interior-wet minimum.
NOTE A minimum DCOF of 0.42 applies to a level interior floor walked upon when wet while wetter and sloped classifications require higher values, the result is meaningful only for the classification under which it was reported, and because slip resistance is a property of the finished surface as installed and maintained the value alone does not predict whether a slip will occur but provides a comparative basis for selecting a finish. (6.6.3)
7 Setting Materials
7.1 Setting Method
Thin-bed (thin-set) — gauged stone over a flat, sound substrate
Medium-bed mortar — large units and slightly variable thickness, sloped floors
Thick-bed (full mortar bed) — variable-thickness cleft stone, leveling required, exterior
7.1.1The setting method shall match the stone form, the substrate flatness, and the service.
7.1.2The method shall be drawn from the TCNA Handbook or NSI Dimension Stone Design Manual and shown on the details. NOTE The thin-bed method bonds gauged stone to a flat substrate and is the standard for calibrated stone tile, the medium-bed method uses a mortar applied in a thicker bed for large units and modest thickness variation, and the thick-bed full mortar-bed method accommodates variable-thickness cleft stone, establishes slope to drains, and remains the most robust method for cleft slate, sloped wet-area floors, and demanding exterior work. (7.1.3)
7.2 Bonding Mortar Type
Modified dry-set cement mortar (ANSI A118.4) — general durable stone, floors and walls
Improved modified dry-set cement mortar (ANSI A118.15) — large units, slabs, demanding bond
Epoxy mortar (ANSI A118.3) — moisture-sensitive stone, chemical exposure, maximum bond
Dry-set cement mortar (ANSI A118.1) — absorptive stone over a cured mortar bed
7.2.1The bonding mortar shall be selected for the stone type, the substrate, and the service, shall comply with the governing ANSI A118 specification, and shall be approved by its manufacturer for the specific stone.
7.2.2Where a fast-setting or rapid-cure mortar is needed, it shall be a product the stone manufacturer approves for the stone, because some rapid-set mortars develop heat or alkalinity that stains sensitive stone.
NOTE Mortar selection for stone is not interchangeable with tile practice, because the stone's moisture sensitivity, translucency, and the staining risk from the mortar itself all govern the choice, and the wrong mortar produces warping, picture-framing, or staining that no later remedy can fully correct. (7.2.3)
NOTE Modified dry-set cement mortar (ANSI A118.4) is the default for durable non-sensitive stone, improved modified mortar (ANSI A118.15) provides higher bond and coverage for large units and slabs, epoxy mortar (ANSI A118.3) is required for moisture-sensitive stone and chemical exposure, and unmodified dry-set mortar (ANSI A118.1) suits absorptive stone over a cured Portland-cement mortar bed. (7.2.4)
7.3 Moisture-Sensitive Stone
○ Epoxy mortar (ANSI A118.3) with 100% coverage — required for serpentine 'green marble' and other moisture-sensitive stone
○ Manufacturer-approved non-water setting system for the specific sensitive stone
○ Not applicable — stone is not moisture-sensitive
7.3.1Moisture-sensitive stone — chiefly serpentine "green marble," and certain marbles, slates, and resin-backed stones identified by the fabricator — shall be set only with an epoxy mortar conforming to ANSI A118.3, or another non-water-bearing system the stone manufacturer approves, applied to achieve full (100 percent) coverage.
7.3.2The Contractor shall confirm with the fabricator whether each stone is moisture-sensitive before selecting a mortar.
7.3.3The Contractor shall not set a moisture-sensitive stone with any water-bearing cement or latex mortar under any circumstances.
NOTE Moisture-sensitive stone absorbs water from a water-based cement or latex mortar and warps, curling its edges away from the substrate and destroying the bond, whereas epoxy mortar contains no water and sets these stones without driving the warping, and full coverage prevents any joint or edge from absorbing water or being left unsupported. (7.3.4)
7.4 White Mortar for Translucent and Light Stone
○ White-pigmented setting mortar required — translucent, white, and light-colored stone
○ Standard (gray) mortar acceptable — opaque, dark, or dense stone
7.4.1White marble, onyx, light limestone, and other translucent or light-colored stone shall be set with a white-pigmented setting mortar to prevent shadowing of the stone color.
7.4.2The Contractor shall verify the stone's translucency on the mock-up and select the mortar color accordingly.
NOTE A gray cement mortar shows through a translucent or thin light stone and shadows or darkens its appearance unevenly, a defect known as telegraphing that cannot be corrected after setting, and only a white mortar preserves the true color of the stone. (7.4.3)
7.5 Crack-Isolation Membrane
○ Required over the full floor — concrete subject to shrinkage cracking or minor in-plane movement
○ Required at existing cracks and joints only (spot membrane)
○ Not required — substrate sound and not subject to in-plane cracking
7.5.1A crack-isolation membrane conforming to ANSI A118.12 and installed per ANSI A108.17 shall be provided where the substrate is subject to minor in-plane movement or shrinkage cracking that would otherwise telegraph through and crack the stone.
7.5.2Structural and moving joints shall be carried through the stone as movement joints regardless of any membrane, because a crack-isolation membrane addresses minor in-plane movement only and does not substitute for the movement joints required by EJ171.
7.6 Waterproof Membrane
○ Required — showers, wet areas, exterior, and over occupied space
○ Required at shower receptors and pans only
○ Not required — interior dry application
7.6.1A load-bearing bonded waterproof membrane conforming to ANSI A118.10 and installed per ANSI A108.13 shall be provided in showers, steam rooms, wet areas, exterior installations, and any stone assembly over occupied or moisture-sensitive space.
7.6.2Where a single membrane is selected for both the waterproofing and crack-isolation functions, the Contractor shall verify it is certified to both standards.
NOTE Stone and cementitious joints are not waterproof, since water passes through joints and through absorptive stone over time, and a continuous bonded waterproof membrane keeps water out of the structure and limits the moisture that drives efflorescence and staining, while many ANSI A118.10 membranes also satisfy the crack-isolation requirements of A118.12. (7.6.3)
8 Joint Materials
8.1 Grout and Pointing
High-performance cement grout (ANSI A118.7) — general stone floors and walls
Standard cement grout (ANSI A118.6) — interior light-duty
Epoxy grout (ANSI A118.3) — chemical exposure, food service, maximum stain resistance
Unsanded cement grout — narrow joints in polished stone (prevents scratching)
8.1.1The joint filler shall be selected for the joint width, the stone finish, the service, and the stain- and chemical-resistance requirement, and shall comply with the governing ANSI specification.
8.1.2For narrow joints in polished stone, an unsanded grout shall be used because the sand in a sanded grout scratches a polished surface during tooling and cleaning.
8.1.3Grout containing pigments or aggressive constituents that could stain a sensitive or absorptive stone shall not be used without the stone manufacturer's confirmation.
8.1.4Absorptive and sensitive stone shall be pre-sealed before grouting where the grout would otherwise stain the stone.
NOTE High-performance cement grout (ANSI A118.7) is the general default for stone floors and walls, and epoxy grout (ANSI A118.3) is used where chemical resistance, maximum stain resistance, or a non-absorptive joint is required. (8.1.5)
8.2 Grout Joint Width
0.06250.375
0.06250.1250.18750.250.375
Default: 0.125 in
8.2.1The joint width shall be selected for the stone size, edge type, and thickness variation, and shall not be less than the minimum the stone's dimensional variation warrants.
NOTE Gauged stone with a precise edge can take a narrow joint while cleft and tumbled stone with irregular edges requires a wider joint, because running a joint narrower than the stone's dimensional and thickness variation produces visible lippage and uneven joints. (8.2.3)
9 Movement Joints
9.1 Movement Joint Design
9.1.1Movement joints shall be provided throughout stone work in accordance with the TCNA movement-joint guideline EJ171, and their locations shall be shown on the stone shop drawings and details before any stone is set. 9.1.2Interior field movement joints shall be provided at the spacing EJ171 establishes for interior conditions, commonly on the order of 20 to 25 feet in each direction.
9.1.3Exterior installations, and interior installations exposed to direct sunlight or to moisture and wide temperature swings, shall have field movement joints at substantially closer spacing, commonly on the order of 8 to 12 feet in each direction, because the larger thermal and moisture movement of an exposed assembly builds destructive stress over a shorter run.
9.1.4The closer of the EJ171 requirement and any project-specific requirement governs.
9.1.5Perimeter movement joints shall be provided where stone abuts restraining surfaces, walls, columns, curbs, and dissimilar floors.
9.1.6Movement joints shall be carried through over every structural, cold, and control joint in the substrate and at every change in substrate plane or material.
9.1.7Movement joints shall be left open of grout and filled with the specified sealant or fitted with a preformed movement-joint profile.
NOTE Movement joints allow the assembly to expand and contract without building the compressive stress that causes stone to tent, debond, and crack, and omitting field movement joints in a large floor is a leading cause of catastrophic failure because thermal and moisture expansion with no place to go lifts the stone off the floor in a ridge. (9.1.8)
9.2 Movement Joint Filler
○ Field-applied elastomeric sealant over backer rod / bond breaker
○ Preformed metal or rigid movement-joint profile
○ Preformed flexible movement-joint profile
9.2.1Movement joints shall be filled with an elastomeric sealant of the type and color specified, installed over a backer rod or bond breaker so the sealant adheres only to the two joint faces and can stretch and compress, or shall be fitted with a preformed movement-joint profile suited to the traffic and exposure.
9.2.2The sealant shall be a non-staining sealant compatible with the stone, verified non-staining on the specific stone where the joint is in contact with absorptive stone.
9.2.3The sealant or profile shall be capable of the movement the joint will see.
NOTE A movement-joint sealant must adhere only to the two joint faces so it can stretch and compress freely, because bonding to the joint bottom restrains and tears it, and many common sealants bleed plasticizers that stain absorptive stone, so a sealant tested non-staining on the specific stone is required. (9.2.4)
10 Substrate Preparation
10.1 General Substrate Requirements
10.1.1The substrate shall be structurally sound, clean, dimensionally stable, and free of dust, paint, oil, grease, curing and sealing compounds, sealers, laitance, efflorescence, and any other bond-inhibiting substance.
10.1.2Concrete substrates shall be fully cured and shall present an open, absorptive surface; troweled-smooth, sealed, or curing-compound-treated concrete shall be mechanically abraded or shot-blasted to an open profile before stone is set, because the setting mortar bonds mechanically and cannot grip a sealed or contaminated surface.
10.1.3The Contractor shall verify the condition of the substrate before installation and shall not set stone over a noncompliant substrate.
NOTE Setting stone over a noncompliant substrate transfers a known defect into the finished work, which is why the condition of the substrate is the Contractor's responsibility to verify before installation. (10.1.4)
10.2 Flatness Tolerance
○ 1/4 in in 10 ft and 1/16 in in 1 ft (gauged stone with all edges under 15 in)
○ 1/8 in in 10 ft and 1/16 in in 2 ft (large units and slabs, any edge 15 in and over)
○ Per the requirement for the stone size, form, and method
10.2.1The substrate shall meet the flatness tolerance required for the stone size, form, and method.
10.2.2High spots shall be ground down and low spots filled with a cementitious patching or self-leveling underlayment compatible with the setting system.
10.2.3Where cleft variable-thickness stone is set by the thick-bed method, the mortar bed accommodates substrate variation, but the finished stone surface shall still meet the flatness and lippage tolerances of this standard.
NOTE For gauged stone with all edges under 15 inches the recognized tolerance is 1/4 inch in 10 feet and 1/16 inch in 1 foot, while for large units and slabs with any edge 15 inches and over it tightens to 1/8 inch in 10 feet and 1/16 inch in 2 feet, because a large rigid unit will rock on an undulation a small unit would tolerate. (10.2.4)
10.3 Substrate Type Verification
Concrete slab — cured, sound, profiled
Cementitious backer unit over framing — walls and floors
Cured Portland cement mortar bed (thick-bed)
Existing sound tile / terrazzo (bond-coat or membrane over)
10.3.1The setting system and method shall match the substrate type.
10.3.2Stone over wood-framed floors shall be set over an appropriate backer board or uncoupling/crack-isolation membrane rated for the stone, and the floor deflection shall be verified within the limit the stone tolerates.
10.3.3Stone shall not be set over a deflecting floor regardless of the mortar.
NOTE Stone over wood-framed floors requires a stiff floor and an appropriate backer board or membrane because wood expands, contracts, and deflects with moisture and load and will crack stone bonded directly to it, and heavy or large stone over wood framing requires verifying the floor deflection is within the limit the stone tolerates. (10.3.4)
11 Installation
11.1 Layout and Blending
Blend / random — distribute natural variation evenly
Book-match — mirror-matched adjacent slabs
Slip-match (side-slide) — repeating vein run
Vein-directional — consistent vein direction
As detailed on drawings
11.1.1The Contractor shall establish the layout from the control lines and setting-out points shown on the finish plan and stone layout so that border and cut units are balanced and of adequate width, full units fall at the most prominent locations, vein and pattern align and match as the design requires, and movement joints fall where the design and EJ171 require. 11.1.2Because natural stone varies, the Contractor shall dry-lay and blend the stone from several crates at once, distributing the natural range of color, vein, and shade across the work so that no concentration of dark, light, or heavily veined pieces forms a blotch, and shall obtain the Architect's approval of the dry-laid blend and vein match before setting.
11.1.3Layout and blending shall be completed and approved before any mortar is spread.
11.1.4Where book-match, slip-match, or directional veining is specified, the stone shall be sequenced and oriented to achieve the match shown on the shop drawings, and the fabricator's numbered layout shall be followed.
NOTE Book-matched and directional work is unforgiving, since a single piece set out of sequence or rotated breaks the pattern, which is the reason approved numbered shop drawings and crate sequencing are required. (11.1.5)
11.2 Mortar Application and Coverage
11.2.1Bonding mortar shall be applied with the trowel notch, technique, and open time the mortar and stone require, combed in one direction with directional troweling, and the stone set with a slight perpendicular movement to collapse the ridges and eliminate voids.
11.2.2The mortar coverage achieved beneath the stone shall be not less than 80 percent for interior dry applications and not less than 95 percent for exterior, wet, and heavy-load applications, with full coverage at edges and corners and no voids beneath.
11.2.3Moisture-sensitive stone shall achieve full (100 percent) coverage.
11.2.4Large units, slabs, and all floor stone shall be back-buttered in addition to combing the substrate to achieve the required coverage.
11.2.5Stone shall be set with full mortar coverage at all edges and corners and with no voids beneath, verified by periodic removal and inspection of set stone.
NOTE Inadequate coverage is a leading cause of stone cracking, debonding, and hollow floors, because a stone bridging a void fractures under load and an edge void admits water, and the required coverage cannot reliably be achieved on a large or floor unit by combing the substrate alone, which is why such units are back-buttered. (11.2.6)
11.3 Beating-In and Lippage Control
11.3.1Floor stone shall be beaten in or rolled with a beating block or the manufacturer's tool, and large units and slabs shall be set with a mechanical lippage-control (leveling) system where required, to seat the stone fully into the mortar, collapse the ridges, and bring adjacent edges into plane within the lippage allowance.
NOTE Polished and honed stone makes lippage conspicuous under reflected light, so the lippage tolerance is tighter and the leveling discipline more important than for textured tile. (11.3.2)
11.4 Grouting and Pointing
11.4.1Grouting shall not begin until the bonding mortar has cured for the period the mortar manufacturer requires, typically not less than 24 to 72 hours.
11.4.2Absorptive and sensitive stone shall be sealed with an impregnating sealer before grouting where the grout would otherwise stain the stone face.
11.4.3Joints shall be cleaned of mortar and debris to a uniform depth, the grout worked fully into the joints to fill them solid, the excess struck off, and the surface cleaned promptly to remove grout residue before it cures onto the stone.
11.4.4For polished stone, an unsanded grout shall be used and the cleaning performed before any abrasive residue can scratch the finish.
11.4.5Joints intended to function as movement joints shall be left open of grout and shall not be filled with grout under any circumstances.
NOTE Grouting before the bonding mortar has cured disturbs the bond, and grouting absorptive or sensitive stone without first sealing it lets grout pigment stain the stone face permanently. (11.4.6)
11.5 Curing and Protection
11.5.1The completed stone shall be protected from traffic and from other trades during the cure period and shall not be exposed to water, washing, or traffic until the setting and grouting materials have cured for the period they require, typically not less than 7 days for cementitious materials.
11.5.2Floors shall be protected with a breathable covering that does not trap moisture against the stone, does not transfer color or adhesive, and does not stain the stone.
11.5.3Protective coverings and tapes in contact with stone shall be verified non-staining for the specific stone.
11.5.4Heavy construction traffic, rolling loads, and point loads shall be kept off the floor until cure is complete.
NOTE Many common protective films and tapes stain absorptive and polished stone, so only products verified non-staining on the specific stone may be placed in contact with it. (11.5.5)
12 Field Testing and Inspection
12.1 Bond and Installation Inspection
○ Yes — full-area sounding and visual inspection under permanent lighting
○ No
12.1.1After installation and cure, the stone shall be inspected for full bond, with no hollow-sounding (unbonded) units, no lippage exceeding the allowance, no cracked, chipped, or warped units, uniform joints fully packed and free of voids, correct vein match and shade blend, the specified finish uniform and free of scratches and grout residue, and movement joints correctly formed and left open of grout, under the permanent or equivalent lighting.
12.1.2Stone shall be sounded — tapped to detect the hollow ring of an unbonded unit — across the floor, and hollow or unbonded units shall be removed and reset.
12.1.3The Contractor shall confirm by periodic removal of set stone that the required mortar coverage was achieved across the work.
NOTE Sounding the stone to detect the hollow ring of an unbonded unit, and periodic removal of set stone, are the means by which bond and the achieved mortar coverage are confirmed after cure. (12.1.4)
12.2 Stone Property Verification
NOTE Stone is a natural material whose properties vary across a quarry; verification testing of the actual supplied lot guards against substitution of a weaker or more absorptive stone than was certified. (12.2.1)
○ Required — test supplied lot against governing ASTM specification
○ Not required — manufacturer certification accepted
12.2.2Where required by the contract documents or where the stone source is unverified, samples of the supplied stone shall be tested by an independent laboratory for the physical properties of the governing ASTM specification (absorption per ASTM C97, compressive strength per ASTM C170, flexural strength per ASTM C880 or modulus of rupture per ASTM C99, and abrasion per ASTM C1353 for floor stone) to confirm that the delivered stone meets the certified values.
13 Cleaning, Sealing, and Protection
13.1 Cleaning
13.1.1After cure, the stone shall be cleaned of grout residue, construction soil, and marks using only cleaners the stone manufacturer permits for the specific stone and finish.
13.1.2Acidic cleaners shall not be used on calcareous stone (marble, limestone, travertine, serpentine) because acids etch and dissolve the surface, dulling polish and pitting the stone.
13.1.3Abrasive pads and powders shall not be used on polished finishes because they scratch the surface.
13.1.4The permitted cleaners and the prohibited cleaners for each stone shall be recorded in the maintenance instructions.
NOTE Acids etch and dissolve calcareous stone and abrasive pads and powders scratch polished finishes, and because the permitted and prohibited cleaners differ by stone and finish they must be recorded so the Owner does not damage the stone in service. (13.1.5)
13.2 Sealing
Penetrating impregnating sealer — absorptive interior stone (marble, limestone, travertine, slate)
Penetrating sealer rated for wet / exterior service
Pre-grout impregnating sealer plus final sealer — stain-prone absorptive stone
No sealer — dense low-absorption stone (most granite, dense quartzite) where not required
13.2.1Absorptive stone shall be sealed with a penetrating impregnating sealer compatible with the stone and finish, applied after the stone and grout have cured for the period the products require, to reduce absorption, staining, and etching susceptibility.
13.2.2The sealer shall be a penetrating impregnating type compatible with the stone and finish; film-forming sealers shall be used only where the manufacturer recommends them for the specific stone.
13.2.3The sealer, the resealing interval, and the application method shall be documented in the maintenance instructions.
NOTE A penetrating impregnating sealer is preferred over a film-forming sealer for floors because a topical film wears unevenly, can reduce slip resistance, and traps moisture, stain-prone absorptive stone may require a pre-grout sealer in addition to the final sealer, and dense low-absorption stone that does not benefit from sealing need not be sealed. (13.2.4)
14 Delivery, Storage, and Handling
14.1Stone, setting materials, grout, membranes, sealers, and accessories shall be delivered in the manufacturer's original packaging with labels and crate markings intact, identifying stone, finish, size, and block/lot.
14.2Stone shall be stored indoors where practicable, protected from weather, freezing, staining, and breakage, and kept off the ground on non-staining dunnage.
14.3Cardboard, wood, and adhesives that stain absorptive stone when wet shall be kept from contact with the stone faces.
14.4Cementitious setting materials and grout shall be stored dry and off the floor, and material that has hardened or exceeded its shelf life shall be discarded.
14.5Epoxy and polymer components shall be stored within their storage-temperature window and discarded when their limited shelf life is exceeded.
14.6Slabs shall be transported, stored, and handled in A-frames and moved with the clamps and frames the fabricator requires, because an unsupported slab cracks under its own weight.
14.7All stone for a continuous area should be from the same block or lot wherever possible, because color, vein, and shade vary between blocks and a block change within a single visual field is apparent.
NOTE An unsupported slab cracks under its own weight, cardboard, wood, and adhesives that contact stone faces when wet stain absorptive stone, and color, vein, and shade vary between blocks, so material handling and lot control protect both the integrity and the appearance of the stone. (14.8)
15 Warranty
1 year (materials)
As offered by the manufacturer for the products specified
1 year from substantial completion
2 years from substantial completion
15.1The stone supplier and setting-material manufacturers shall warrant their products against manufacturing and material defects for the period offered, and where a setting-material manufacturer offers an owner-registered system warranty covering the membrane, mortar, and grout as an installed system, that warranty should be obtained and executed in the Owner's name.
15.2The Contractor shall warrant the installation — including substrate preparation, membrane and mortar selection and application, mortar coverage, vein match and shade blend, lippage and joint quality, grouting, movement-joint formation, and sealing — against defective workmanship for the project warranty period.
NOTE Manufacturer system warranties are typically void unless the complete tested system was installed per the manufacturer's instructions and the cited TCNA method or NSI detail, including the epoxy and white-mortar requirements for moisture-sensitive and translucent stone, and the installation record is part of the warranty basis. (15.3)
NOTE Failures arising from substrate movement where required movement joints were omitted, from warping of moisture-sensitive stone set with a water-bearing mortar, from water intrusion where a required waterproof membrane was omitted, from cleaning or sealing contrary to the manufacturer's instructions, or from loads exceeding the rated service are excluded from both warranties, and variation in color, vein, and shade within the approved range is an inherent characteristic of natural stone and not a defect. (15.4)
16 Spare and Extra Materials
16.1The Contractor shall deliver to the Owner spare stone of each type, finish, and size installed, in the percentage of installed area stated, in full crates labeled with the stone, finish, size, and block/lot.
16.2Spare stone shall be stored by the Owner in a dry, protected location on non-staining dunnage.
NOTE Attic stock from the same block or lot is especially important for natural stone because later-quarried replacement stone will differ in color, vein, and shade and cannot be matched, and the spare material allows the Owner to repair damage with stone that matches the original installation. (16.3)