1、Designation: C842 05 (Reapproved 2015)Standard Specification forApplication of Interior Gypsum Plaster1This standard is issued under the fixed designation C842; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification covers the minimum requirements forfull-thickness (in accordance with Table 1) interior gypsumplastering on g
3、ypsum, metal, masonry, or monolithic concretebases designed or prepared to receive gypsum plaster.1.1.1 Gypsum plaster applied to the interior side of exteriorwalls of masonry or concrete shall be isolated from the exteriorwall.1.2 Gypsum plasters shall not be used in exterior locationsor interior “
4、wet” areas.NOTE 1To secure desirable results, this specification should becoordinated with the provisions of Specification C841. General informa-tion concerning full thickness gypsum plastering is contained in AnnexA2, Annex A3, and Annex A4.1.3 Details of construction for a specific assembly toachi
5、eve the required fire resistance shall be obtained fromreports of fire-resistance tests, engineering evaluations, orlistings from recognized fire testing laboratories.1.4 Details of construction to achieve required sound con-trol shall be obtained from reports of tests conducted atrecognized sound t
6、esting laboratories in accordance with theapplicable sound tests of Test Methods E90, C423,orE492.1.5 The values stated in inch-pound units are to be regardedas the standard. The SI (metric) values given in parentheses areapproximate and are provided for information purposes only.1.6 The text of thi
7、s standard references notes and footnoteswhich provide explanatory material. These notes and footnotes(excluding those in tables and figures) shall not be consideredas requirements of the standard.2. Referenced Documents2.1 ASTM Standards:2C5 Specification for Quicklime for Structural PurposesC11 Te
8、rminology Relating to Gypsum and Related BuildingMaterials and SystemsC28/C28M Specification for Gypsum PlastersC35 Specification for Inorganic Aggregates for Use in Gyp-sum PlasterC59/C59M Specification for Gypsum Casting Plaster andGypsum Molding PlasterC61/C61M Specification for Gypsum Keenes Cem
9、entC206 Specification for Finishing Hydrated LimeC423 Test Method for SoundAbsorption and SoundAbsorp-tion Coefficients by the Reverberation Room MethodC631 Specification for Bonding Compounds for InteriorGypsum PlasteringC841 Specification for Installation of Interior Lathing andFurringC1489 Specif
10、ication for Lime Putty for Structural PurposesE90 Test Method for Laboratory Measurement of AirborneSound Transmission Loss of Building Partitions andElementsE492 Test Method for Laboratory Measurement of ImpactSound Transmission Through Floor-Ceiling AssembliesUsing the Tapping Machine3. Terminolog
11、y3.1 Definitions:3.1.1 Definitions shall be in accordance with TerminologyC11.3.2 Definitions of Terms Specific to This Standard:3.2.1 catfaces, nblemishes or rough depressions in thefinish coat.3.2.2 coat, na thickness or layer of plaster applied over asurface in a single application.3.2.2.1 base c
12、oat, nthe sum of the scratch and brown coatsor the total coats in place prior to application of finish coats.3.2.2.2 brown coat, nthe second coat of plaster applied inthree-coat work.3.2.2.3 finish coat, nthe last coat of plaster applied ineither two-coat or three-coat work.3.2.2.4 scratch coat, nth
13、e first coat of plaster applied overa lath or other substrate.3.2.2.5 three-coat work, nplaster applied in three succes-sive coats, leaving time between coats for setting or drying, orboth, of the plaster.1This specification is under the jurisdiction of ASTM Committee C11 onGypsum and Related Buildi
14、ng Materials and Systems and is the direct responsibilityof Subcommittee C11.03 on Specifications for theApplication of Gypsum and OtherProducts in Assemblies.Current edition approved Oct. 1, 2015. Published October 2015. Originallyapproved in 1976. Last previous edition approved in 2010 as C842 05
15、(2010)1.DOI: 10.1520/C0842-05R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International
16、, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.2.6 two-coat work, nscratch and brown coats appliedfrom the same mix with no time allowed for setting of thescratch coat before the brown coat is applied.3.2.3 gypsum ready mixed plaster, ncalcined gypsumplaste
17、r, mixed at the mill with a mineral aggregate, designed tofunction as a base coat to receive various finish coats.3.2.4 metal bases, nexpanded metal, welded or wovenwire, or punched sheet metal plaster bases.3.2.5 smooth-trowel finish, na finish resulting from steeltroweling.3.2.6 texture finish, na
18、 finish resulting from (1) trowelapplication followed by floating or texturing of the surface withany of a variety of tools using a minimum of water or (2)machine application which is or is not hand textured.4. Delivery of Materials4.1 All manufactured materials shall be delivered in theoriginal pac
19、kages, containers, or bundles bearing the brandname and manufacturer (or supplier) identification.5. Protection of Materials5.1 Plasters and other cementitious materials shall be keptdry until used; they shall be stored off the ground, under cover,and away from walls with condensation and other damp
20、surfaces. Metal products shall be protected, while stored,against rusting.6. Environmental Conditions6.1 TemperaturesWhere the ambient outdoor temperatureat the building site is less than 55 F (13 C), a temperature ofnot less than 55 F (13 C) and not more than 80 F (27 C)shall be maintained continuo
21、usly inside the building for aperiod of not less than one week prior to the application ofplaster (Note 2). Temporary heat shall be evenly distributed,using deflective or protective screens to prevent concentratedor uneven heat or cold on the plaster, and maintained until thepermanent HVAC system is
22、 activated.NOTE 2The requirement should minimize the possibility of plastercracking due to structural movements caused by thermal changes fromoutdoor temperature extremes during construction.6.2 VentilationSufficient ventilation shall be provided toremove excess water given off through the drying pr
23、ocess. (SeeAppendix X2 for provisions for ventilating underside of roofsand glazed buildings with and without operable windows.)7. Materials7.1 Gypsum PlastersThe following plasters shall conformto Specification C28/C28M:7.1.1 Ready mixed.7.1.2 Neat.7.1.3 Wood-fibered.7.1.4 Gauging for finish coat.7
24、.2 Gypsum Casting and Molding PlastersSpecificationC5, C59/C59M.7.3 Gypsum Keenes CementSpecification C61/C61M.7.4 Lime:7.4.1 Finishing Hydrated LimeSpecification C206, TypeS.7.4.2 Quicklime for Structural PurposesSpecification C5.7.4.3 Lime Putty for Structural PurposesSpecificationC1489.7.5 Lime P
25、uttyLime putty exceeding 8 weight % ofunhydrated magnesium oxide shall not be used for finish coatplaster.7.6 Aggregates:7.6.1 Aggregates for Base Coat PlasterSpecification C35.7.6.2 Aggregates for Finish Coat PlastersSpecificationC35, except that gradation shall be within the limits specifiedin Tab
26、le 2.7.6.3 Sand for job mixed lime putty-gypsum gauged, sandfloat finish (see 9.6.6.1) shall be graded within the limitsspecified in Table 3.7.7 WaterWater used in mixing and finishing plaster shallbe potable, and free of such amounts of mineral or organicsubstances that affect the set, the plaster,
27、 or any metal in thesystem.NOTE 3Water containing salt or alum, or water in which tools havebeen washed, accelerates the “set” and may cause efflorescence. Waterfrom stagnant pools and wells frequently contain organic or vegetablematter which may retard the “set,” cause staining, or interfere with t
28、hebond.7.8 Bonding CompoundsSpecification C631.TABLE 1 Thickness of PlasterPlaster BaseThickness of Plaster Including FinishCoat, in. (mm)Metal plaster base58 (16) minAll other types of plaster base12 (13) minUnit masonry58 (16) minMonolithic concrete surfaces:AVerticalBC 58 (16) minHorizontalC 18 (
29、3) to58 (16)ABase coat plastering of the same proportions as specified for unit masonry is notprohibited from being used over plain or reinforced monolithic concrete, providedthe surface is first covered with a metal plaster base or first coated with a bondingcompound.BFinish coat plaster applied di
30、rect to a bonding compound over vertical monolithicconcrete shall be not more than316 in. (4.8 mm) in thickness. Where morethan316 in. of finish coat is required to bring such vertical surface to a true plane,a base coat of plaster shall first be applied to the bonding compound.CWhere horizontal or
31、vertical monolithic concrete surfaces require morethan38 in. (9.5 mm) or58 in. (15.9 mm) of plaster, respectively, to producerequired lines or surfaces, metal plaster base shall be attached to the concretebefore application of plaster. Where concrete surface requires the application ofmore than 1 in
32、. (25.4 mm) of plaster to produce required lines or surfaces, lathshall be applied over furring secured to the concrete.Typo corrected editorially October 2010.TABLE 2 Aggregate for Finish Coat Plasters, PercentageRetained on Each Sieve, CumulativeSieve SizePerlite, Natural and Manufactured SandVolu
33、me,% Weight, %max min max minNo. 20 (850 m) 0 . 0 .No. 30 (600 m) 10 . 0.5 .No. 100 (150 m) 100 40 100 40No. 200 (75 m) 100 70 100 70C842 05 (2015)28. Surface Preparation8.1 SubstratesSurfaces of substrates for the application ofgypsum plaster shall be free of materials that will inhibit bondor adhe
34、sion, shall be straight, plumb, level, square, and true torequired plan angles and curves. See A2.5.8.1.1 All accessories shall be securely attached to thesubstrate and be installed to accommodate embedment offlanges.8.1.2 Gypsum and Metal LathShall have been installed incompliance with Specificatio
35、n C841.8.2 Conditioning of SurfacesAll depressions in masonryand concrete surfaces deeper than18 in. (3.2 mm) shall bebrought flush to the surface with compatible materials prior toplaster application. Fins or protrusions extending morethan116 in. (1.6 mm) from the surface shall be removed.Protrusio
36、ns less than116 in. (1.6 mm) shall be feathered outwith compatible materials prior to plaster application.8.2.1 MasonryAll masonry surfaces shall be wetted im-mediately prior to the plaster application. No free water shallremain visible on the substrate surface.8.2.1.1 Where the surface is too smoot
37、h to provide mechani-cal key, the surface shall be roughened or bonding compoundshall be used. (See Annex A2.5 and A2.6.)8.2.1.2 Where bond cannot be obtained over the entiresurface by the methods specified in 8.2.1.1, self-furring metallath shall be used in accordance with Specification C841.8.2.2
38、Monolithic concretebonding compounds shall beused prior to plastering all monolithic concrete surfaces. (SeeA2.6.)8.2.3 Grounds, beads, and screeds shall be installed prior tothe plastering as modified herein.8.3 Grouting:8.3.1 Metal bases for solid partitions shall be grouted withgypsum plaster lea
39、ving14 in. (6.4 mm) below the top edge ofthe base, and be formed with a center groove so that the lathextends34 in. (19 mm) below the top edge of the base, orplaster grout shall be placed after installation of lath.8.3.2 Metal FramesHollow door and window frames shallbe filled with gypsum plaster gr
40、out.9. Mix Design9.1 Mixing, GeneralAll plaster mixing shall be done bymechanical means unless hand mixing is specified.9.1.1 Retempered, partially set, frozen, caked or lumpymaterial shall not be used.9.1.2 Each batch shall be mixed separately and mixers shallbe free of all set and hardened materia
41、ls prior to mixing eachbatch.9.1.3 All tools shall be kept clean.9.1.4 The setting time shall be not more than 4 h.9.2 Hand Mixingsee Annex A3.1.9.3 Mechanical MixingIn accordance with manufacturersprinted directions. See Annex A3.2.9.4 Base Coat Proportions:9.4.1 Gypsum Neat PlasterProportions of s
42、and, perlite, orvermiculite aggregate to 100 lb (45.4 kg) of gypsum neatplaster shall be not more than those specified in Table 4. (SeeA2.3 for equivalent measure for aggregates.)9.4.2 Gypsum Ready Mixed PlasterShall be used with theaddition of water only.9.4.3 Gypsum Wood-Fibered PlasterProportion
43、of damp,loose sand or perlite or vermiculite shall be not more than 1 ft3(0.028 m3) to 100 lb (45.4 kg) of gypsum wood-fibered plaster.9.5 Preparation of Lime Putty:9.5.1 Lime putty shall be prepared from Type S hydratedlime or pulverized quicklime, in accordance with the manufac-turers printed dire
44、ctions.9.5.2 Hydrated LimeType S lime shall only be used aftersoaking for the time period required in accordance with themanufacturers printed directions.9.6 Finish Coat Proportions:9.6.1 Finish coats shall be either ready mixed or job mixedin accordance with Table 5 and Table 6.9.6.1.1 Where thickn
45、ess of the finish coat is more than18 in.(3.2 mm), the proportion of the gypsum gauging plaster shallbe increased to minimize shrinkage type cracks.9.6.2 Troweled Finishes of lime putty gauged with gypsumgauging plaster or ready mixed gypsum plaster shall beproportioned in accordance with Table 5.9.
46、6.2.1 Where finish in 9.6.2 is to be applied over base coatscontaining perlite or vermiculite, the addition of not lessthan12 ft3(0.014 m3) or not more than 1 ft3(0.028 m3)offineaggregate meeting the sieve analysis of Table 2 shall be addedto the mix.9.6.3 Troweled finishes of lime putty gauged with
47、 gypsumKeenes cement shall be specified as medium or hard and shallbe proportioned in accordance with Table 5.9.6.3.1 When finish in 9.6.3 is mechanically mixed, thewater shall be placed in the mixer first, then the lime, the fineaggregate (if used), and finally the gypsum Keenes cement.9.6.4 Trowel
48、ed finishes of gypsum ready mixed plaster shallbe mixed in accordance with Table 5.9.6.5 Float finishes of lime putty gauged with gypsumgauging plaster shall be proportioned in accordance with Table5.9.6.5.1 When finish in 9.6.6 is to be mixed with sand, thesand shall be graded within the limits sho
49、wn for basecoats inSpecification C35 except that all of the sand shall pass a No. 8(2.36 mm) sieve.9.6.6 Float finishes of lime putty gauged with gypsumKeenes cement shall be proportioned in accordance with Table5.9.6.6.1 When the finish in 9.6.6 is to be mechanically mixedwet, follow procedures in 9.6.3.1. For mixing dry, add limefirst, then gypsum Keenes cement, and sand. This dry mixTABLE 3 Sand for Job-Mixed Lime Putty-Gypsum Gaged SandFloat Finish, Percent Retained on Each Sieve by Weight,CumulativeS
