Homeownersconsumer Countertop

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A Homeowners Guide to

Natural StoneCountertop Installation


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1. Introduction ........................................1

2. Stone Materials ...................................1

(Varieties: Granites; Marbles, Serpentinesand Onyxes; Slates; Limestones andTravertines; Stone Tiles)

3. Communicating with Your Contractor..2

(Documentation; You and Your SubcontractorsResponsibilities; Shop Drawings; StoneSlab Layout)

4. Cabinet and Substrate Requirements..3

(Measurement Tolerances; Subtops;Cabinet Doors, End Panels and Hardware)

5. Field Measurements ............................3

(Cabinet Components)

6. Design Considerations ........................3(Joinery Layout (Seam Placement); Spansand Cantilevers; Sink Mounts; Edge Profiles;Corner Embellishments; Backsplashes)

7. Quality Fabrication Methods ..............4

(Finishing Edge Profiles; Cutouts forAuxiliary Equipment)

8. Installation Methods ...........................5

(Dry Assembly; Shims; Adhesive; FinalPositioning and Joint Filling;

Sealer Application)9. Tolerances............................................5

(Joint (Seam) Widths; Lippage; Slab Thickness;Exposed Edges; Joints at MaterialsTransition; Slab Flatness and Levelness)

10. Adhesives and Joint Fillers..................6

(Types; Seam Filler Materials)

11. Stone Tile Countertop Considerations ..7

(Subtops; Edge Treatment; Stone TileTolerances; Joint Widths; Vein Trend;

Shading Variation; Splashes; BackButtering; Tile Reinforcement)

12. Resin-Impregnated Slabs.....................8

(Description of Procedure;Design Considerations)

13. Reinforcement Techniques...................8(Fiberglass Mesh; Liner Blocks; Splines;Rodding)

14. Allowable Repair .................................9(Fissures; Cracks; Chips; Pitting)

15. Maintenance ......................................10

(Application of Sealers; Topical Sealers;Impregnators; General Precautions;Care and Cleaning Practices)

16. Stone Swatches and Installations .....11

17. Drawings

RC-001Kitchen Layout ......................................13

RC-002Kitchen Layout ......................................14

RC-003Corner Joinery Examples ......................15

RC-004Typical Joinery at Kitchen Sink .............16

RC-005Detail of Rodding Reinforcement..........17

RC-006Undermount Sink Support Details ........18

RC-007Support Details for Heavy

(Enameled Cast-Iron) Sinks...................19

RC-008Support Details for Rimmed or

Drop-In Sink Styles........................20

RC-009Vanity Top Details .................................21

RC-010Stone Shelf Details.................................22

RC-011Cantilever Supports...............................23

RC-012Edge Profile Nomenclature ...................24

Table of Contents

Disclaimer

This document is written as a general guideline. TheMarble Institute of America and its Member companieshave neither liability nor can they be responsible to anyperson or entity for any misunderstanding, misuses, ormisappliation that would cause loss or damage of anykind, including loss of rights, material, or personalinjury, or alleged to be caused directly or indirectlyby the information contained in this document.

28901 Clemens RoadSuite 100Cleveland, OH 44145440.250.9222www.marble-institute.com


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2008 Marble Institute of America Page 1

NATURAL STONECOUNTERTOP

INSTALLATION

1. INTRODUCTIONThe beauty and permanence of natural stonecountertops are enjoyed by many. The fullpotential of any installation is realized onlywhen the selection, design, fabrication, andinstallation are completed by, or with theconsultation of, qualified and experiencedindividuals. This document has beenprepared and published by the Marble

Institute of America to help guide consumersthrough the process professional fabricatorsuse when using natural stone as a countertopsurface.

2. STONE MATERIALSVarieties. Many varieties of natural stonehave been used successfully for countertopsurfaces. However, different types of stonehave specific properties that offer advantagesor disadvantages in various applications. The

following is a brief overview of the commonvarieties of stone used as countertops.

Granites are undoubtedly the most popularstone type used in countertop applicationstoday. This group of stones includes manystone materials that are not true granites bygeological definition. However, because theirproperties are so similar, the AmericanSociety for Testing and MaterialsInternational (ASTM) lumps them together as

granite. These stones are knowngeologically as gabbro, anorthosite, gneiss,diabase, and diorite, to name a few.Whatever the name, these stones are some ofthe hardest of the common countertopstones, offering high levels of resistance toabrasion and scratching. The primaryminerals in granite are resistant to almost all

chemicals commonly found in a home;however, there may be trace mineralspresent in some granites and granite-likestones that are vulnerable to some acids.

Marbles, serpentines, and onyxes aretraditionally prized for their aesthetic appeal,accentuated by distinct veining and oftenbold colors. They are relatively softer thangranite, although some serpentines are asdense as some granites. Marbles can bescratched by kitchen utensils so it is best touse cutting boards and other protectivemeasures. Use only non-abrasive productswhen cleaning marble.

Marbles can also be etched by chemicalattack. These stones are calcium carbonate-based and are damaged by exposure to acidicsolutions such as lemon juice, tomatoes,vinegar, etc. The use of inappropriatecleaning agents may also trigger acidic attack.Acidic solutions can permanently etch thesurface of the material. The application of asealer will reduce, but not eliminate, thevulnerability to acidic attack. For thesereasons, your stone dealer may notrecommend marble for use in kitchens.

Slates have high resistance to chemicals andhave been traditionally used as chemistrylaboratory tops. However, slates are softerthan granite and therefore vulnerable toscratching and abrasion. Slate has a naturalcleft (not a smooth surface). Some suppliersprovide slate slabs that are not honed. Bespecific about the kind of finish you desire.The same precautions mentioned for marbleswith regard to damage should be applied to

slates.

Limestones and travertineare calciumbased similar to marble. Therefore, they havethe same weaknesses as marbles when used ascountertops. Abrasion damage is a concern,particularly if the stone is polished. Manyvarieties of these stone types will absorb


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Page 2 2008 Marble Institute of America

water to some degree and must be sealed tohelp protect them.

Stone tiles can be used as a countertopsurface material. The finished surface will

carry the same precautions as the particularstone type from which it is made. The jointfiller, whether grout, plastic sealant, epoxyor resin, may have specific requirements forprotection and maintenance. Follow therecommendations of the manufacturer of thematerial.

3. COMMUNICATING WITH YOURCONTRACTORDocumentation. As dictated by standard

practices of good business, allcommunications MUST be documented inwriting.

All natural stones are unique. Some have pits,fissures, cracks, corrosive minerals, or otherfeatures that you may find objectionable.These should be acknowledged and pointedout to you when samples and/or slabs arebeing viewed. You need to be aware thatsome of these features may become more or

less noticeable when the position (vertical orhorizontal) of the slab is changed, or whenthe lighting intensity is changed.

You and Your SubcontractorsResponsibilities. Cabinetry installation,plumbing rough-in, electrical rough-in, etc.are usually required to be completed by you,or by subcontractors coordinated by you.These should be specifically addressed inwriting. Your stone contractor will install

your stone, not connect electricity or water.

Granite is heavy! Please have a clear pathfrom your driveway to your kitchen so thatinstallation crews can navigate through yourhome easily. Please have walkways free ofice, snow and clutter. Also, if you haveexisting countertops, please make sure they

are removed BEFORE installation. Also,make sure that your installation date does notconflict with other work being done in yourhome (wood floor finishing, tile installation,other tradesmen, etc).

Shop Drawings can effectivelycommunicate exact cutting information toyou. A shop drawing is a highly detaileddocument that will identify all aspects of thefinished product installation. The shopdrawing is prepared by your fabricator,showing the layout of the stone pieces,location and size of all seams, and detailsclarifying all corner and edge treatmentconditions. Some fabricators produce full sizetemplates that are highly detailed. Thesedetailed templates may be considered fullsize shop drawings. Whatever the format,you will review and approve this documentprior to the start of fabrication. This is thetime to ask questions about seam placement,cutouts, etc.

Stone Slab Layout. When working withhighly variegated materials, insist that youparticipate in the layout of the actual stoneslabs. This is very important and highlyrecommended so that you can fullyunderstand what can or cannot bedone. Keep in mind that the pricing maychange if you decide to have the stone cut ina certain way that causes unnecessary waste.

4. CABINET AND SUBSTRATEREQUIREMENTSCabinets and any trim that affects the overallsize of the stone countertops must be

permanently installed in their final positionprior to field measuring for countertops.

Measurement Tolerances. Top surfacesof the stone cabinets must be within 1/8" (3mm) of flat and level when measured across adistance of 10'- 0" (3 m). Wall surfaces toreceive stone backsplashes must be plumb


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and within 1/8" (3 mm) of a true plane whenmeasured across a distance of 10'- 0" (3 m).When cabinets are not within thesetolerances, you (or your AuthorizedRepresentative), will be asked for permission

to proceed with the installation. Installingcabinetry outside of these tolerances willrequire excessive shim spaces and wideregions of filler material. Any necessaryaesthetic improvements to conceal thiscondition (e.g., additional wood trim) maybe your responsibility.

Subtops. Fragile stone varieties may requirea full subtop to support the stone. Generally,sound varieties of granites and marbles can beused in thicknesses of 20 mm (") or greaterwithout the use of a subtop. However, thepresence of aesthetically pleasing butunsound veins, cracks, or excessive fissuringwill mandate the use of a subtop, regardlessof thickness. Appropriate materials forsubtops are marine-grade plywood, exterior-grade plywood, waterproofed medium-density particle board, or furring strips.Excessive weight requirements, like that of aheavy cast-iron sink, may require the use ofeither a subtop or auxiliary framing to carryhe weight of the sink and its contents. Water

weighs around 8lbs. per gallon. Some ofthe larger sinks can easily hold 10 gallons ormore. Thats an additional 83 pounds (ormore) hanging under your counter!

Cabinet doors, end panels, andhardware must be installed before the fieldmeasurements are made. Upper cabinets areusually required prior to installation if a fullheight backsplash is to be installed. If not,then it is best to position them after the stoneinstallation.

5. FIELD MEASUREMENTSCabinet Components. Fieldmeasurements are taken once all cabinetshave been installed in their permanent

positions. The following related componentsmust be available to the Technician at thetime of measurement (templating):

Cabinet Doors

End Panels

Cabinet Hardware Sinks (and Manufacturer-supplied

templates)

Plumbing Fixtures

Cook Tops

Exhaust Vents (when full-heightsplash is required)

Electrical Outlets (roughed in)

Refrigerators (in some cases)

6. DESIGN CONSIDERATIONSJoinery Layout (Seam Placement). Thelayout of the joinery (seams) of thecountertops is extremely important to theoverall appearance upon completion. Detailson drawings RC-001, -002 and -003 show avariety of joinery schemes. Make sure youunderstand where seams will be and howseams may affect the overall appearance ofthe stone. This is especially true wheninstalling some of the higher-end varieties

with obvious veins and movement.

Spans and Cantilevers. In designs wherepart of the countertop is spanning betweensupports, the length of the span shall belimited to 2'- 0" (600 mm) for " (20 mm)stone thicknesses and 3'- 0" (900 mm) for1" (30 mm) stone thicknesses. In designswhere the countertop is cantilevered oroverhanging the supports, the cantilever shallbe limited to 6" (150 mm) for " (20 mm)

thick countertops and 10 (250 mm) for 1"(30 mm) countertops, but in no case may thecantilevered portion represent more than1/3 of the width of the countertop.Cantilevered countertops exceeding thesedimensions will require corbelled supportsbeneath the stone. The exposed underside ofcantilevered portions of countertops will be


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sawn or otherwise unfinished surfaces. Note:Fragile stones may require corbelled supportsfor cantilevers that are less than thosespecified.

Sink Mounts. Sinks are supplied in one ofseveral types: Top mount, (or self-rimming),undermount, and farm-home. In the case ofthe top-mounted sinks, the weight of the sinkand its contents are transferred to the topsurface of the stone counter via the rim of thesink. Undermount sinks can be anchored tothe underside of the stone countertop orcarried by a subtop. A subtop or auxiliaryframing may be required for either designwhen more fragile stones are used, or whenthe sink (with contents) is excessively heavy.Refer to details on drawings RC-008 throughRC-011 for examples of sink mounting.Note: cast iron sinks will always require theextra support stated above for both top andundermount types.

Edge profilesor silhouettes; add eleganceto the finished project. Edge profiles withnarrow projections and sharp corners aremore susceptible to chipping than those witha larger, curved silhouette. Examples of edgeprofiles commonly used are included ondrawing RC-016. With machinery andtooling available to modern fabrication shops,many custom profiles can be created whichare not shown here. Ask your fabricator ifyou have something special in mind. Yourselection of an edge detail will likely influence the

cost of your countertops more than any other

decision you make.

Corner Embellishments. Corners of stone

countertops can be cut square, cut to aradius, or projected.

Backsplashes. Partial backsplashes usuallyrange from 4" to 8" high. Full-heightbacksplashes cover the entire area betweenthe countertop and the upper cabinets.

Backsplashes are normally made of the samethickness as the countertop material. Thisallows the Fabricator better yield from theslabs, as the narrow strips will aid in thelayout efficiency, and it also provides better

color match. Mixing materials of twodifferent thicknesses requires using stoneslabs sawn from two different blocks, andcolor variation can be pronounced.However, some Fabricators have themachinery to plane down backsplashes usingthe same slab or block of material to get athinner splash and match the rest of thecounters. On stones with obvious veining,the vein of the splash should match thecountertop below.

Backsplashes are not assumed to be part ofthe job and must be specified if you wantthem.

7. QUALITY FABRICATIONMETHODSFinishing Edge Profiles. Professionallyfinished edge profiles will be a constantthickness and smooth along the entire length.Edges are finished to the same type and

quality of surface as the top, unless acontrasting edge surface has been specifiedfor accent purposes. When working withresin treated slabs, exact color matchbetween the edge surface and the top surfacemay not be achievable.

Cutouts for auxiliary equipment mustconform to equipment templates, withallowable tolerances. Please verify that theequipment templates match the equipment

you are installing. There have been caseswhere the supplied manufacturer templatesdid not match the sink, cooktop, etc. In theinterest of safe handling, some cutouts maybe partially or completely performed in yourhome after installing your stone.


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8. INSTALLATION METHODSDry Assembly. At the project site, it isrecommended that all stone pieces be dryassembled in place to verify satisfactory fitprior to the application of adhesive.

Shims are commonly employed to level thestone countertops. Shim material may bewood or plastic. Maximum spacing betweenshims is 2'- 0" (600 mm). Alternatively,longer spacing between shims may be used ifthe stone is supported with anoncompressible filler material (usuallyepoxy or polyester resin). This practice isoften referred to as hard packing.

Adhesive. The stone countertops aresecured to the substrate with a nonstainingadhesive. Common construction adhesives orsilicone sealant are the most popularmaterials used.

Final Positioning and Joint Filling.Final positioning of the stone is done eithermanually or with the aid of commerciallyavailable stone-alignment tools. Filling theseams is normally completed prior to final

positioning of the stone units, allowing thefiller material to extrude out of the joint asthe stones are pulled into alignment. Thestone surface may be masked to preventcontact by the filler material.

Sealer Application. After the countertopsare installed and the seams are filled, a sealeror impregnator may be applied. Refer to theReinforcement Techniques section below forfurther discussion of these applications.Alternatively, some fabricators prefer toapply the sealer or impregnator in thefabrication shop prior to transporting thepieces to the project site.

9. TOLERANCESThe tolerances listed here are achieved usingskilled tradesmen following standard industry

workmanship practices. Due to variations infabrication equipment and stock availability,these tolerances may not be achievable, or insome cases, closer tolerances may beachievable. Therefore, for any particular

project, you and your contractor may agreeto tolerances that are more or less stringentthan those listed here. Such agreementsshould be documented in writing. Unlessotherwise agreed, the tolerances listed hereare acceptable guidelines.The tolerances in this section pertain to largestone panel-type countertops only.Tolerances for stone tile countertops arelisted below, in Adhesives and Joint Fillers.

Joint (seam) widthsbetween two stoneunits should equal 1/16" (1.5 mm), with atolerance of 1/64" (0.4 mm). In suchcases where a larger joint width has beenspecified, the tolerance is to be 25% ( )of the nominal joint width. Joint width doesnot include the dimension of an arris(a smallchamfer, approximately 1/16 x 1/16) onthe stone edge. When an arris is used, theperceived joint width may be greater than theactual width due to the seam filler occupyingthe width of the arris.

Lippage. In the stone industry, the termlippage refers to the unevenness of the

finished surfaces of two adjacent stone units.Due to the relatively tight seams used incountertop installations, even minor amountsof lippage are noticeable. Lippage may beunavoidable due to permanent warp in the


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slab stock. There should be no detectablelippage at the front or rear edge of thecountertop. Maximum allowable lippage atthe center of the countertop is 1/32" (0.8mm). See sketch that follows for

clarification.

Slab Thickness. The thickness of thestone slabs used in a given project shallnot vary by more than 1/8" (3 mm)

between the thickest and thinnest slabs.

Exposed edges of adjacent stone slabs mustbe matched in thickness and properlyinstalled so that neither the top nor bottomsurface exceeds lippage tolerances.

Joints at Materials Transition. Visiblejoints between stone and other materials(e.g., cabinetry, gypsum wall board) shall be1/8", with a tolerance of 1/16" (1.5mm), and filled with a soft, elastic material.Exceptions to this would be the jointbetween a full height backsplash and theunderside of the upper cabinets, which is tobe a nominal " with a tolerance of 1/8"(3 mm). Concealed joints between the

stone and other construction materials (e.g.,stone-to-wall joint underneath thebacksplash) shall be sized to ensure aminimum of 1/8" (3 mm) of cover.

Slab Flatness and Levelness. Individualstone slabs are to be flat within 1/16" (1.5mm) when measured with a 4'-0" (1.2 m)straight edge. Finished countertop surfacesincluding multiple stones are to be both flatand level to 1/8" (3 mm) across 10'- 0"

(3 m).

10. ADHESIVES ANDJOINT FILLERSTypes. Adhesives used for stone installationcan be either standard construction adhesivesor elastic sealants with strong bondingproperties to both the stone and thesubstrate. Construction adhesives will

normally provide greater bond strength,while elastomeric sealants will provide someforgiveness for movement within the cabinetand subtop underneath. Excessive movementof the substrate, regardless of the type of

adhesive used, will result in the cracking ofseams or the stone itself. Verify that theproduct used does not stain the stonematerial.

Seam Filler Materials. Seams in the stonecountertop are usually filled to the level ofthe top surface. The most common fillermaterials are polyester resin, epoxy resin,elastomeric sealant, and grout. Elastomericsealants can be made from silicon,polyurethane, or acrylic bases.

11. STONE TILE COUNTERTOPCONSIDERATIONSSubtops. Stone tile countertops must have asubtop made of minimum 3/4" exterior

grade plywood or " cementitious backerboard. Subtop must be flat to within 1/8 in10'- 0".

Edge Treatment. Exposed edges of the

countertop may be finished by providing anedge profile strip of stone, wood, or metal.Where stone is employed, it is to be used asan apron to the top surface stone, whichlimits stress on the countertop/apron joint.

Stone tile tolerances for all stone typesmust be 1/32" (1 mm) in length, width, andthickness.

Joint Widths. Unless otherwise agreed,

joint widths for stone tile countertops mustconform to the following: Stone-to-walljoints must be 1/8" (3 mm) in width. Stone-to-stone joints must be 1/16" (1.5 mm)minimum, 3/32" (2 mm) maximum, anduniform from stone to stone. Stone-to-cabinetry joints must be 1/8" (3 mm) inwidth.


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Vein Trend. When using stone tiles withobvious veining, all tiles shall be installedwith the vein running in the same direction.

Shading Variation. Stone tiles are subject

to manufacturing processes different fromstructural stone. There is great latitude in theacceptability of shaded stones. Ask theInstallers to lay out the stone for yourinspection and approval.

Splashes must be stone tile, minimum of 4"high.

Back buttering of all stone tiles isrequired. This technique applies a portion ofthe installation material to the back face ofthe stone. It requires placement of one-halfof the setting material in the case of thin-setmortar, epoxy, or non water-solubleadhesive, or a lesser quantity of very richmortar in the case of Portland cement, to theback of the stone, while the balance of thesetting material is applied to the bed.Application should be performed so that onepass is completed in a north-south direction,while the second pass is performed in an east-west direction, thus ensuring, as close aspossible, 100% contact of the stone to theinstallation bed.

Tile Reinforcement. A commonreinforcement for fragile stone tiles is toapply a fiberglass mesh to the back surface ofthe tile. The adhesive used in this applicationis commonly an epoxy or polyester resin.When this type of reinforcement is adheredto the tiles, the Installer must use a thin-setmaterial that will bond to the resin-

impregnated backer. Most often this willrequire an epoxy-based, rather than aPortland-based, thin-set compound.

12. RESIN-IMPREGNATED SLABSThe application of resin to the surfaces ofstone slabs has become an ever-increasing

practice. The intent of this procedure is to fillpits, cracks, and fissures of natural stoneswith a glossy resin to enhance the appearanceof the polished slab. When received, theresin treatment is usually easily detected by

viewing the raw edges of the slab. Evidenceof excess resin is usually visible on the edgesof the slab if the stone has been treated.

Description of Procedure. The processinvolves evenly applying the resin on thesurface of the cleaned, sawn slab. This isfrequently done in an automated process,although some suppliers will do thismanually. Depending on the equipment used,the slab may be placed over a large vacuumtable to draw the resin deeper into the stone.The resin is allowed to cure, which may ormay not be accelerated with heat application.Once the resin has cured, the slab is polished.The polishing grinds most of the resin fromthe stone surface, so that it remains only indepressions and some inter-crystallineregions of the slab. The amount of surfacearea that remains as resin varies due to thenatural features of the material, but it isusually a fraction of one percent (1%).

The resin used in this process is commonly anepoxy, polyester, or acrylic based polymer.Design Considerations. While the intentof this process is to provide a cosmeticallymore attractive surface, you should be awareof several characteristics of resined stone:

Color. The resin applicationnormally makes the color of thestone somewhat darker than anuntreated slab. This becomes an issuewhen finishing the edges of thecountertop, as the color of the edgewill be lighter in appearance than thecolor of the face surface. Severalproducts are marketed in theindustry for darkening the edge, butnone have been found to beuniversally successful.


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Interaction with Sealers. Therehave been cases of incompatibilitybetween a given resin and fabricator-applied sealer combination. Thisusually results in a cloudy or

blotchy appearance after the sealerproduct has been applied.

Structural Flaws. The resinprocess can hide cracks or otherblemishes which are structurallyinfluential features of the material.Assessment of the structuralworthiness of the material can bemade more difficult as a result.

UV Light Exposure. Nearly all ofthe resins currently in use are

vulnerable to color change or surfacedegradation when exposed toultraviolet light. These materials aretherefore not suitable for exteriorapplications.

13. REINFORCEMENT TECHNIQUESAs products of nature, stones have varyingstrength and behavioral properties. Stones oflesser soundness or stones that have hadsubstantial areas removed from the slab (e.g.,

sink cutouts) will benefit from reinforcementby a variety of techniques.

Fiberglass Mesh. A commonreinforcement for stone slabs of limitedsoundness is to apply a fiberglass mesh to theback surface of the slab. The fabricatorcompletes this process in the shop. Theadhesive used in this application is commonlyan epoxy or polyester resin.

Liner Blocks. Although not frequently usedin stone countertop construction, a linerblock of stone material can be adhered to theunderside of the stone slabs (when no subtopis used) to reinforce seams or othervulnerable areas. The liner block need not beof the same type of stone material as thecountertop.

Splines. Seams, particularly those betweennarrow stone pieces, are often put togetherusing a steel or stainless steel key.Commonly, a large washer is used as thespline key. The metal is fully encapsulated

with polyester or epoxy resin and fitted toclosely cut slots in the stone, similar to thebiscuit joint reinforcements used inwoodworking.

Rodding. A commonly seen method ofcountertop reinforcement is the techniquereferred to as rodding. Rodding isbeneficial to narrow strips of stone material,such as those in front or behind sink or cooktop cutouts. This technique requires ashallow kerf(a narrow cut or groove) in theunderside of the stone slab. The kerf is thenclosely fitted with a metal or fiberglass rod,which is then fully embedded in epoxy orpolyester resin. The rod has greaterresistance to bending than the stone and helpsprevent the stone from bowing. A strip offiberglass mesh backing is often applied overthe rodded region for additionalreinforcement.

14. ALLOWABLE

REPAIR

Stone countertops in need of repair requirecompetent, experienced artisans to achievethe desired results. Repairing stone ispermitted when the refurbished region is notin a structurally significant area of thecountertop, and when it can be accomplishedskillfully so that the repair is consistent incolor and texture with the rest of the slab.

Fissures occur naturally in many stonetypes. A fissure is defined by the AmericanGeological Institute as an extensive crack,break, or fracture in the rock, which maycontain mineral-bearing material. The termfissure is used commercially in the stoneindustry to describe a visible separation alongintercrystalline boundariesor the voids betweenmineral crystals. This separation may start


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and stop within the field of the stone orextend through an edge. A fissure differsfrom a crack in that it is a naturally occurringfeature in the stone.

Cracks occur in stones as a result ofmechanically induced stresses duringhandling, fabrication, transport, orinstallation. When cracks are detected in slabmaterial prior to fabrication, the best methodis to simply avoid them during the layoutprocess. In stones with lesser soundnessproperties, this option may not be practical,or possible. When working with such stonesit is common practice to repair cracks bycementing them together with epoxy orpolyester resin, either with or without dowelreinforcement. Cracks that occur as a resultof handling-induced stresses are often moredifficult to repair, as they commonly includechipping in addition to the crack. Repair isfrequently performed by injection of apenetrating resin adhesive, which may bedyed to match the stone, and then rebuffingthe area after curing of the resin. In manycases, the entire stone must be repolished tomake the repair unnoticeable. If the repair isattempted but unsuccessful, the stone is to bereplaced with a new piece.

Chips can occur in stones either as a resultof sawing operations or handling and restraintdevices. Particularly in the igneous stonevarieties, the exiting portion of the diamondblade will create many small chips. A smallchamfer, called an arris, of approximately1/16" x 1/16" (1.5 x 1.5 mm) can be usedto eliminate most of these small chips. Theuse of an arriswill make the seam appear

wider than its actual dimension when filled.Larger chips may be repaired with epoxy orpolyester resin if the completed repair isconsistent in color and texture withunrepaired areas of the slab. In manymaterials, the resin used in the repair willappear more natural if it is not dyed.

Pitting of the countertop surface,particularly in granite material, is acommonly seen characteristic on naturalstone. Granites are made up of severaldifferent minerals, each mineral having a

different hardness. Granites contain quartz,feldspars, biotite, amphibole, ferroustitanium oxides, and other mineralcombinations. On the Mohs Scale (see inserton page 7), diamonds are the hardestmineral, with a rating of 10. Quartz andfeldspar have a hardness of 6.5 to 7 and arevery durable. Biotite (also known as mica) onthe other hand is very soft (2.5) and flakeseasily. All true granites have biotite in theircomposition. Because biotite is relatively softand flaky, the first few layers are removedduring the polishing process, causing pitsthroughout the slab. Some granites havemore biotite throughout their compositionthan others. The higher the biotite content ofthe stone, the more pits it will have. Mostpolished igneous rocks will have varyingdegrees of pits, depending on the amount ofbiotite, muscovite, and phlogopite in theircomposition.

The pits do not make the granite less durableor otherwise inferior, and do not inthemselves qualify the slab for replacement.Pits are common in all granites and should beexpected when dealing with a natural,polished stone containing several types ofminerals of varying hardness. It is usually bestto not attempt repair of pits, as most repairtechniques will not cosmetically improve thecountertop.

15. MAINTENANCEApplication of Sealers. The application ofa topical sealer or impregnator is a commonstep in decreasing the vulnerability of thestone to stains.

Topical sealers cure as a film on the stonesurface. Since the material is actually


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covering the stone, the appearance of thestone surface may be altered by theapplication of this type of product. Thismaterial will provide somewhat of asacrificial layer over the stone, and will

absorb most of the wear on the countertop.Since the sealer is softer than the stone,normal use of the countertop will result inabrasion of the sealer surface and dictatereapplication to maintain the original lusterof the surface. A properly applied topicalsealer will normally reduce, although noteliminate, the vulnerability of calcareousstones to attack from mildly acidic solutions.

Impregnators will penetrate the stone andcure a few millimeters below the surface,residing in the microscopic spaces betweenthe minerals in the stone. These products donot actually seal the stone, and are morecorrectly referred to as a repellent ratherthan a sealer. As such, they are formulated toprevent transmission of liquids, whileallowing transmission of vapor (not unlikebreathable fibers). Since they reside belowthe actual surface of the stone, the change tothe appearance of the stone surface isminimal. Impregnators will be eitherhydrophobic, in that they repel water-basedfluids only, or oleophobic, repelling both oiland water-based fluids. The Manufacturer ofthe impregnator product will recommend areapplication interval.

General Precautions. When any surfaceprotection product is used, care must betaken to read and follow the Manufacturerswritten instructions accurately. This willprovide the greatest benefit from the

application and will guarantee safe handlingof the product.

Care and cleaning practices.The natural stone you have purchased foryour home or office is an investment that willgive you many years of beautiful services.Stone is a natural product and simple care

and maintenance will keep it lookingbeautiful. Make sure you understand whichmethods are best for your particular stonecountertop. Ask your fabricator for the MIAbrochure Care & Cleaning for Natural Stone

Surfaces.For more information visithttp://www.usenaturalstone.com/care/index.cfm


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* Source: The Reduction of E. Coli on Various Countertop Surfaces, by Dr. O. Peter Snyder, Jr., Ph.D., of the Hospitality Institute of Technology and Management, March 1999.** Source: A Study of the Cleanability of Marble and Granite Countertop Materials, by Dr. O. Peter Snyder, Jr., Ph.D., of the Hospitality Institute of Technology and Management, February 2006.

Marble Institute of America and its Member companies are not responsible for any use or misuse that causes damage of any kind, including loss of rights, materials, and personal injury alleged to be caused directly or indirectly by the information

www.marble-institute.com

Granite Countertops:#1 in Cleanability!

Butterfly Green Granite

In a recent study, granite countertopsprovided the greatest reduction inbacteria counts of all materialstested! Six countertop surfaceswere contaminated with E. colibacteria, then washed and rinsedusing dish soap and normal andreasonable cleaning practices.

A follow-up study evaluated thedifferences in cleanability of threecommon unsealed natural stonesused for countertop surfaces againstan engineered stone. Overall, therewas no statistical difference inreduction after wash and rinse forany of the four surfaces.**

Granite .......................36,000 to 1*

Stainless Steel ...............4,000 to1Concrete ........................2,400 to 1Tile ...................................900 to 1Wood................................500 to 1Plastic Laminate...............285 to1

Reduction in BacteriaAfter Washing & Rinsing:

Genuine Stone and the Genuine Stone sealare trademarks of the Natural Stone Council.


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All rights reserved. No part of this document may be reproduced

or transmitted in any form or by means electronic or mechanical,

including photocopy, recording, or by an information storage

For over sixty years, the Marble Institute of America has served as

the authoritative source of information on standards of naturalstone workmanship and practice and the suitable application ofnatural stone products.

Membership in the association is worldwide and includes naturalstone producers, exporters/importers, distributors/wholesalers,fabricators, finishers, installers, restoration/maintenance specialistsand industry suppliers all committed to the highest standards ofworkmanship and ethics.

MIA publishes a monthly newsletter for members, markets a rangeof technical publications and consumer pamphlets on naturalstone, sponsors business and technical meetings and seminars onindustry-related topics, provides educational programming for

architects and construction specification professionals, and conductsthe Rocky Advertising Awards and the annual Pinnacle Awardscompetitions recognizing outstanding natural stone projectsworldwide. MIA also sponsors an industry accreditation programfor high quality fabricators and commercial installers.

MIA is also a leading promoter of stone usage in the commercialand residential marketplaces. MIA produces a number of consumereducation materials on the use of natural stone and its proper careand maintenance and hosts an informative website for consumersatwww.usenaturalstone.com.

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Homeownersconsumer Countertop

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