1、GA-214-10GYPSUM ASSOCIATIONRecommendedLevels ofFinishGypsumBoardThe Finishing insomegeographicareasthislevelisreferredtoas“fire-taping.”Whereafire-resistanceratingisrequiredforthegypsumboardassembly, details of construction shall be in accordance withreports of fire tests of assemblies that have met
2、 the fire-ratingrequirement. Tape and fastener heads need not be coveredwithjointcompound.Specified where gypsum board is used as a substrate fortile; may be specified in garages, warehouse storage or othersimilar areas where surface appearance is not of primaryconcern.The weight, texture, and sheen
3、 level of wallcoveringsapplied over this level of finish should be carefully evaluated.Joints and fasteners must be adequately concealed if thewallcovering material is lightweight, contains limited pattern,has a gloss finish, or any combination of these finishes ispresent. Unbacked vinyl wallcoverin
4、gs are not recommendedoverthisleveloffinish.This level of finish is highly recommended where paint isspecifiedorwhereseverelightingconditionsoccur.This highest quality finish is the most effective method toprovide a uniform surface and minimize the possibility of jointphotographing and of fasteners
5、showing through the finaldecoration. A skim coat of joint compound is intended toconceal small imperfections in joints and on the surface of thegypsum board, smooth the texture of the paper, minimizedifferences in surface porosity, and create a more uniformsurfacetowhichthefinaldecorationcanbeapplie
6、d.A“skimcoat“isessentiallya“film“ofjointcompoundandisnot a readily measurable thickness. There is no specific milthickness that constitutes a proper skim coat. A skim coat isdescribed in the foregoing text as being “trowel applied“ withthe intent being that the consistency (viscosity) of the jointco
7、mpound be such that it can be applied by a trowel. Othertools may be used for application so long as the trowelconsistencyisachieved.The objective of the application is to achieve total cover-age of the entire surface with the skim coat. This is typicallyaccomplished by delivering the compound to th
8、e surface andusing a drywall broad knife to force the compound into thesurface pores and imperfections while shearing off excesscompoundfromthesurface.A skim coat will not approximate a plastered surface.Once the skim coat dries, the gypsum board paper may showthrough and the treated joints, filled
9、voids, and spottedfastenerheadswilllikelybevisible.Typically specified in appearance areas which are toreceive heavy- or medium-texture (spray or hand applied)finishes before final painting, or where heavy-gradewallcoverings are to be applied as the final decoration. Thislevel of finish is not recom
10、mended where smooth paintedsurfacesorlighttomediumwallcoveringsarespecified.This level should be specified where flat paints, lighttextures,orwallcoveringsaretobeapplied.In critical lighting areas, flat paints applied over lighttexturestendtoreducejointphotographing.Paintswithsheenlevelsotherthanfla
11、tandenamelpaintsarenotrecommendedoverthisleveloffinish.Level2:Level3:Level4:All joints and interior angles shall have tape embed-ded in joint compound and wiped with a joint knife leavingathincoatingofjointcompoundoveralljointsandinteriorangles. Fastenerheadsandaccessoriesshallbecoveredwith a coat o
12、f joint compound. Surface shall be free ofexcess joint compound. Tool marks and ridges areacceptable. Joint compound applied over the body of thetape at the time of tape embedment shall be considered aseparate coat of joint compound and shall satisfy theconditionsofthislevel.All joints and interior
13、angles shall have tape embed-ded in joint compound and shall be immediately wipedwith a joint knife leaving a thin coating of joint compoundover all joints and interior angles. One additional coat ofjointcompoundshallbeappliedoveralljointsandinteriorangles. Fastenerheadsandaccessoriesshallbecoveredw
14、ith two separate coats of joint compound. All jointcompound shall be smooth and free of tool marks andridges. Note:Itisrecommendedthatthepreparedsurfacebe coated with a drywall primer prior to the application offinal finishes. See painting/wallcovering specification inthisregard.All joints and inter
15、ior angles shall have tape embed-ded in joint compound and shall be immediately wipedwith a joint knife leaving a thin coating of joint compoundover all joints and interior angles. Two separate coats ofjointcompoundshallbeappliedoverallflatjointsandoneseparate coat of joint compound shall be applied
16、 overinterior angles. Fastener heads and accessories shall becovered with three separate coats of joint compound. Alljointcompoundshallbesmoothandfreeoftoolmarksandridges. Note:Itisrecommendedthatthepreparedsurfacebe coated with a drywall primer prior to the application offinal finishes. See paintin
17、g/wallcovering specification inthisregard.Level5:All joints and interior angles shall have tape embed-ded in joint compound and shall be immediately wipedwith a joint knife leaving a thin coating of joint compoundover all joints and interior angles. Two separate coats ofjointcompoundshallbeappliedov
18、erallflatjointsandoneseparate coat of joint compound shall be applied overinterior angles. Fastener heads and accessories shall becovered with three separate coats of joint compound. Athin skim coat of joint compound trowel applied, or amaterial manufactured especially for this purpose andapplied in
19、 accordance with manufacturers recommenda-tions, applied to the entire surface. The surface shall besmooth and free of tool marks and ridges. Note: It isrecommended that the prepared surface be coated with adrywall primer prior to the application of finish paint. Seepaintingspecificationinthisregard
20、IV. :COMMENTSSkim Coatpp,gLevels of Gypsum Board FinishV. RESOURCES:Association of the Wall and Ceiling IndustryCeilings overpainting of textured ceiling surfaces may not be deemednecessary where an adequate amount of material is applied to providesufficienthidingproperties.Adrywallprimermaynotbere
21、quiredundercertain proprietary texture materials; consult with the manufacturer ofthetexturematerialsforspecificrecommendations.A smooth surface may be achieved bylightly sanding or wiping joint compound with a dampened sponge.Care shall be exercised to ensure that the nap of the gypsum boardfacing
22、paper is not raised during sanding operations. For additionalinformation on the finishing of gypsum board surfaces consult ASTMStandardC840.In general:paints with sheen levels other than flat, enamel and dark paint finisheshighlightsurfacedefects;textureshideminorimperfections.NOTICEAll of the state
23、ments, opinions, specifi-cationsandrecommendationsonlevelsof gypsum board finish contained in thispublication are for general informationpurposes only and are not intended toimply that these are the only materials,procedures, processes, or methodswhichareavailableorsuitable.Bypublishingthisdocument,
24、thecosponsoringtrade associations, and their member compa-nies, individually or collectively, make noexpress or implied warranty or other represen-tation as to the quality, characteristics, orsuitability of the materials or techniquesdescribed herein, and specifically disclaim anyimplied warranties
25、of merchantability or fitnessfor a particular purpose which may arise byoperationoflaworotherwise.This document may be revised orwithdrawnfromcirculationatanytime.The status of the document should beverified by the user prior to followingany recommendations containedherein.Toverifythatyouhavethemostcurrent version of the document,access the Gypsum Associationwebsiteatwww.gypsum.org.
