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Indian StandardRECOMMENDATIONSFORMODULAR

CO-ORDINATION INBUILDING INDUSTRY:TOLERANCES

PART 2 PRINCIPLES AND APPLICATIONSf First Revision )

UDC 621~753.1 : 721.013 ( 389.63)

@ BIS 1992BUREAU OF INDI AN STANDARDSMANAK BHAVAN, 9 BAHADUR SH AH ZAF AR MARG

NEW DELHI 110002January 1992 Price Group 7

( Reaffirmed 1996 )

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Planning, Byelaws and Dimensional Co-ordination Sectional Committee, CED 10

FOREWORDThis Indian Standard ( First Revision ) was adopted by the Bureau of Indian Standards, after the draftfinalized by the Planning, Byelaws and Dimensional Co-ordination Sectional Committee had been approvedby the Civil Engineering Division Council.One of the aims of modular co-ordination is to provide compatibility and inter-changeability of compo-nents. In earlier days a practicai system of tolerances was derived as clearance fit, prescribing minustolerances on each component without any allowance to the space in which it is to be placed In the past,the building industry never faced the problem of tolerances,structural engineering. It is a common practice, except in the field of mechanical andto instal readymade doors/windowsets while brickworkis in progress. Any inaccuracies in size, shape or position of doors/windowsets is adjusted by the brickworkand inaccuracies in the brick itself adjusted in mortar joints. The extensive use of prefabricated elementsand componeots in building construction have provoked the concept of tolerance in recent years. Theconcept of tolerance is indeed a tool to be used for dimensional control of the component which can fitwithout any problem ~for size, squareness, bow, plumbness, position and appearance.The value of tolerances is subject to fabrication and assembly of materials, design of moulds and manu-facturing~process. Moreover it can be employed to delimit the dimensional variations for factory producedor site-cast, precast and precast prestressed concrete products. This can be used by designers, architects,engineers, general contractors, manufacturers, erectors, quality control agencies and related or interfacingtrades.This standard is intended to be a working reference for the dimensional control of prefabricated compo-nents and precast concrete products.This standard was originally published as IS 6408 : 1971 Recommendations for modular co-ordinationapplication of tolerance in building industry. In the usage of this standard, a need was felt to cover theterminology in a comprehensive manner in addition to effecting the other technical changes deemednecessary on the basis of the experience gained over the years, As a result, the standard has been publishedin the following two parts:

Part 1 Glossary of terms, andPart 2 Principles and applications.

This part has been made comprehensive by incorporating the advancement made in the field of jointdesign systems and process of manufacture for precast concrete products and other allied componentsemployed in building construction. Further, general concept concerning tolerances for building and buildingcomponents and illustrative examples supported by figures have been included. The derivation of manufac-ture sizes for modular space, calculation of joint clearance, distribution of tolerances, specification oftolerances and indication of tolerances on drawings have also been elaborated to make this standardcomprehensive.In the preparation of this standard considerable assistance has been rendered by the National BuildingsOrganization, New Delhi.In the preparation of this standard due weightage has been given to international co-ordination amongthe standards and practices prevailing in different countries in addition to relating it to the practices in thefield in this country. This has been met by deriving assistance from the following documents:

a) Industrialized building and modular design. Henrik Nissen Cement and Concrete Association,London 1972.b) The principles of modular co-ordination in building ( revised ). CTB W24. The InternationalModular Group 1982.c) Modular co-ordination of low cost housing. United Nations Publications 1970.

( Continued on third cover )

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Indian StandardRECOMMEN-DATIONSFORMODULAR

CO-ORDINATION INBUILDING INDUSTRY:TOLERANCES

PART 2 PRlNClPlES AND APPLICATIONS( First Revision )

1 SCOPE1.1 This standard ( Part 2 ) covers the basicprinciples to be adopted for the inaccuracieswhich occur in setting out of the building on thesites, erecting or manufacturing of buildingcomponents.1;2 This deals with theory and application ofdimensional deviations which shall be limited bythese tolerances in construction industry.1.3 Tolerances are intended to be applied whetheror not a system of dimensional co-ordination isused in design process.2 REFERENCESThe following Indian standards are necessaryadjuncts to this standard:

IS JVO.1077 : 1986

TitleSpecification for commonburnt clay building bricks(fourth revision )

IS No.4993 : 1983

6408( Part 1 ) : 1991

3 ALMS

Recommendations for modularco-ordination buildingindustry : ~Toleraces, Part 1Glossary of terms

3.1 Every process of construction entails somedegree of inaccuracy due to dimensional variationmaterial and methods employed for production.These will become apparent only when compo-nents will not fit into their allocated modularspaces or when spaces between two componentsbecome so large or small that components fail tomeet joint requirements. It becomes necessary toassess the likely variation that may occur in jointclearances in order to select suitable joint techni-ques or building components so designed toaccommodate the extremes of variations ( seeFig. 1 ). Such a process helps to derive the worksize of building components.

FIG. 1 DIMENSI ONALARIATION1

http://../link/10/1077.Bishttp://../link/10/1077.Bishttp://../link/10/1077.Bishttp://../link/31to60/4993.Bishttp://../link/31to60/4993.Bishttp://../link/61to88/6408_1.Bishttp://../link/61to88/6408_1.Bishttp://../link/61to88/6408_1.Bishttp://../link/61to88/6408_1.Bishttp://../link/61to88/6408_1.Bishttp://../link/31to60/4993.Bishttp://../link/10/1077.Bis

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3.2 The pre-requisite to achieve aim of precast,prestressed or prefabricated building components.that are connected on site without shaping, canonly be achieved if components are produced witha suitable degree of accuracy.3.3 The components must fit into their modularzones without an accumulation of error whileinstalling them in position ( see Fig. 2 ).3.4 With the use of the fabricated building com-ponents which are neither intended to nor capa-ble of being shaped on site, it is necessary toobtain certain degree of accuracy in both manu-facturing and placing/assembly.3.5 While preparing dimensional specification andquality requirements of fabricated building com-ponents the~controlling dimensions, basic dimen-sions and tolerances shall be specified by thesupplier to encourage the use of their products inthe construction industry.4 F IELD OF AP P LIC ATION4.1 Der iva t ion of Dimen s ions for Modu larC o x n p o n e n tIn component building design the application ofthe special reference system and the selection ofpreferred sizes for component and space dimen-sions is only the first step towards ensuring thatcomponents as supplied can be assembled withease of fit.4.2 The reference system enables designers torelate the position and size of components bymeans of modular planes. Such co-ordinatingplanes form the boundaries of modular compo-nent spaces and include allowances for inaccuracyand the size clearances.4.3 In modular design practice, therefore, thesespaces shall be defined by co-ordinating dimen-sions which are modular.4.4 It is important to stress the essential theoreti-cal nature of such dimensions in the context ofbuilding component manufacture.

4.5 The modular co-ordination shall provideco-ordinating length, width and thickness ofcomponents. By this, it means it shall provideflexible dimensional compatibility between theposition of different material sub-systems compris-ing the components and positioning anddimensions of these functional sub-systems.4.6 The modular sizes shall provide the basis onlyfor determining the manufacturing sizes ofcomponents as explained in Fig. 3.4.7 Deduction from the modular sizes shallrequire to be made to accommodate any allowancefor joint and for the dimensional deviations thatoccur in production and erection.4.8 Th e S y st em o f To le ra n ces t o M o d u l a rC o m p o n e n t s4.8.1 In this system the space -between modularplanes or gridlines is a whole multiple of thebasic module. This is also the modular size of thecomponent, which is used for architectural designin general arrangement of plans, elevations andsections. For detailed drawings of joints and forspecifying the size to be manufactured, it is neces-sary to consider the aspects given in 4.8.1.1and 4.8.1.2.4.8.1.1 First the width of the joint betweencomponents shall be deducted (Zg) and next anallowance for inaccuracy in erection ( positiontolerance ). These two together comprise theminimum deduction from the modular size togive the maximum size for the component. Thenan allowance is made for inaccuracy in manufac-ture ( the manufacturing tolerance ) and theminimum size for the manufacture component isreached. Care shall be taken that the tolerancesare not so coarse that the maximum deductioncreate too large a space for available techniquesin jointing.4.8.1.2 This being a proven system for derivationof work size to a modular component, furtherguidance shall be required on tolerance values tobe prescribed for gap, position and production.

SPACE

COMPONENT

F IG. 2 MODULAR COMPONENTS2

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Sib6408 ( Part 2 ) : 1992

2g*P*f -4

h

Ic-

-P

-2g*P

-T

MODULAR PLANES

MODULAR SPACE

MODULAR SIZE

MINIMUM GAPS

POSITION TOLERANCE

MINIMUM DEDUCTION

MINIMUM SIZE

MANUFACTURINGTOLERANCE

MINIMUM SIZE

MAXIMUM DEDUCTION

FIG. 3 SYSTEM OF TOLERANCESFOR MODULAR COMPONENTS4.9 Reliable information on the quantification ofbuilding tolerances is hard to find. As someindication of the order of magnitude is to betaken into consideration, values for varioustolerance classes are given in Annex A, which arebased on the experiencep gained in the field byundertaking study and.Bnalysis of actual measure-ments.5 TERMINOLOGYFor the purpose of this standard, the definitionsgiven in IS 6408 ( Part 1 ) : 1990 and IS 4993 :1983 shall apply.6 GENERAL CONCEPT6.1 The concept of tolerances applicable to build-ing and building components is relatively newand less known in our country. Therefore, it isproper to lay down uniform:rules.for application

of tolerances so that manufacturers, designers andbuilders may improve the dimensional control inmanufactured products at design, production andassembly stages.6.2 Small variations in dimensions are unavoid-able in construction industry which can betolerated within certain limits, if the linkage isto be made as designed. The limits of the permis-sible deviations determine the tolerance, that is,permitted deviations for the building componentsand total building unit.6.3 The manufacturing, setting-out and erectiontolerances together shall comprise the constructiontolerance. These shall be determined with respectto construction method adopted for satisfactoryperformance. Sometimes these are also recognizedas product, erection and interfacing tolerances inindustrialized building construction methods.

3

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IS6408 ( Part 3) : las?7 TYPE OF DIMENSIONAL DEVIATIONS7.0 Dimensional deviations are of two types:

a) induced deviations, andb) Inherent deviations.

7.1 Induced deviations are divided in threegroups: namely, (a) manufacturing deviations,(b) setting out deviations, and (c) location devia-tions.7.1.1 Induced deviations shall arise as a result ofmanufacturing and building processes.7.1.2 While selecting the size of components andtheir joints to suit a standard modular component,the inherent deviations are summed arithmeticallyand combined with the statistically summed indu-ced deviations to provide a sensible indication oft h e total allowance for all relevant specifiedpermitted deviations.7.1.3 These geometricalhuman error, inaccuracyin precise measurements,7.2 Inherent deviationsnamely, (a) Irreversible,

deviations are caused byof tools and limitationsfalls in two groups:and (b) reversible.

7.2.1 These shall arise as a result of inherentproperty of materials used in manufacture ofcomponents and elements.7.2.2 The irreversible deviations are caused byinitial shrinkage, settlement and creep.7.2.3 The reversible deviations are caused by thechange in temperature or humidity or by deflec-tion due to live/wind loading.7.2.4 It shall be necessary, when dealing withtolerances, to specify reference conditions, such as, 0 0

CON1 ROLLINGDIMENSION 12 M

(a) choice of jointing technique and selection ofwork size for the components, (b) design of jointto ensure movement which may occur at aparticular place, and (c) large size wall elementsmade of materials having low thermal expansioncoefficients and low moisture movement exposedto weather.7.3 The dimensional tolerance, orientation tole-rance and shape tolerance together shall comprisethe manufacturing tolerance.7.4 The positional and orientation tolerances forarranging components together shall comprise thesetting out tolerance.7.5 The position and orientation tolerances forerection together shall comprise the erectiontolerance.8 DEVIATIONS AND TOLERANCES8.1 Deviations arise in all work processes, produc-tion and assembly. No dimensional specificationcan be fulfilled with 100 percent accuracy.8.2 In order to ensure linkage and correct func-tioning, these deviations shall be limited. Thisshall be done by selecting limits for permissibledeviations.8.3 In construction industry the tolerances shallbe specific-d with f deviations from the specifieddimension which shall be called basic dimension.The basic dimensionshall be within the controllingdimensions ( see Fig. 4 ).8.4 The tolerance shall then be defined as thetotal difference between maximum and minimumpermissible dimensions ( see Fig. 5 ).

6 6 6All dimensions in millimetres.

FLG. 4 CONTROLLI NG DIMENSION AND BASIC DIMENSIONOBSERVED DIMENSION J

m BASIC DiMENSlO N DEVIATIONj -

_MlNIMUM PERMISSIBLE DIMENSION TOLERANCE TMAXIMUM PERMISSIBLE DtMENSlONI

FIG . 5 OBSER VEDDIMBNSION AND DEVIATION4

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8.5 The tolerance specification shall denote thesymmetrical tolerance system.Example:

The length shall be specified by the basicdimensions 2990 mm. It shall be permissiblefor this length to vary between the limits:2985 mm ( minimum permissible dimensions ),and2995 mm (maximum permissible dimensions).

The tolerance shall be 2995 - 2985 9 10 mm.The basic dimensions with tolerances shall beexpressed as 2990 f 5 mm.8.6 In other branches of industry following diffe-rent methods of specifying tolerances are used ondrawings:

+ 15 + 10 +7 + 0 - 52980 2985 2988 2945 3000+ 05 + 0 -3 - 10 - 15

and these five dimensional specifications shallcorrespond to same dimensions and same limitsfor the deviations.8.7 The length obtained by actual measurementof component shall be called as observed dimen-sions and the difference between the length andthe controlling dimension shah denote the devia-tion ( see Fig. 6 ). The deviation shall bereckoned with signs ( f ).

9.5 Measurement of the deviation a of an arbi-trary point~P is achieved in practice from a checkplane ( line ) 3 at known distance 6 from thebasic plane ( or line ) 2 ( see Fig. 6 ).9.6 Flatness Deviations9.6.1 Flatness deviations shall be determined bythe principles as shown in Fig. 7. Deviation is thedistance from any point on the surface to asurface representing a median plane for all fourcorner points.9.6.2 In practice the measurement shall be madefrom a plane exterior to the component andparallel to two main directions of the component.9.6.3. Deviation shall be measured at variouspoints over the entire surface area.9.7 Skewness9.7.1 Skewness is a special case of flatness devia-tion affecting a rectangular surface with welldefined corners ( see Fig. 8 ).9.8 Angular Deviations9.8.1 Correspondingly, angular deviations shallbe expressed in three ways as deviation in length.9.8.1.1 The difference between the observed angleand the basic angle is expressed by means of thelength 1 and d as given below ( see Fig. 9 and

OBSERVED SURFACE

=&g$gFIG. 6 DIWIATION ROMBASIC P LANE exp r essed by a )

9 BASIC SHAPE, OBSERVED SHAPE ANDDEVIATION IN SHAPE9.1 In practice, it is seldom possible to managewith one dimension tolerances. Limits have to beset for the deviation in shape occurring in allthree dimensions of building components.9.2 In case of one dimension tolerance, the pres-cribed shape shall denote the basic shape. Thedifference between the observed and the basicshape shall be called the deviation in shape.9.3 Deviation in length, angle, straightness orplaneness shall be expressed by means of devia-tion in length.

F I G . 7 FLATNESS E VIATION

9.4 The deviations from a plane or a straightnessat one of edges of a member shall be expressedby means of distance from points, lines or planeseon an observed surface ( or curve ) 1, to the basicplane or a line 2 ( see %ig. 6 ). FIG. 8 SKEWNESS5

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IS 6408 ( Part q )JV rSS2Fig. 10 ):

a) Observed angle is more than basic angle : 1b) Observed angle is less than basic angle

( 4 - 11>c) Observed diagonal is less than basic dia-

gonal ( A - dl )

r,AS,C ANG.LE9A

Afi ANGLEBASIC ANGLE96FIG. 9 DEVIATIONIN ANGLE

[ expressed by length I and ( I2 - Z1 ]

1 OBSERVED ANGLEBASIC ANGLEFIG. 10 DEVIATION[ expressed by ( da IN SHAPE- 411

ACTUAL !POSITION I

-----i

-5-----REFERENCEPOSITION

11 A POSITIONAL

9 .9 Se t t ing Out Dev ia t io t i 9.9.1 The setting out deviation shall be determin-ed by the principle as shown in Fig. 11.9 .10 Er ec t ion Dev ia t ion9.10.1 The erection deviation shall be determinedby the principle as shown in Fig, 12.10 BOX P RINCIP LE10.1 Box is the imaginary and arbitrary shapewhich encloses three dimensional space betweentwo forms of surface symmetrical to each otherand are so placed that the distance of each one ofthem is one quarter of a tolerance away from thebasic surface inside and outside directions.10.2 Shape tolerances which are intended tolimit the deviations in a component length, angle,straightness and planeness easily become confus-ing and difficult to apply in practices. The tole-rances on the shape of a component are, therefore,collectively used in box principle.IO.3 Figure 13 shows an arbitrary basic shape lyingbetween an inner and outer figure, the surfaces ofwhich are located symmetrically about the surfaceof the basic figure. One surface shall be locatedT/4 inside the surface of the basic figure, and theother T/4 outside it.10.4 This principle has limitation of adoption inboth shape and size. It delimits the control ofthree length tolerances. However, it does notestablish the inside control of figure.11 COMBINATION OF TOLER ANCES11.1 When a number of components are linked,their partial dimensions and joints shall oftenamount to series of dimensions having a totaldimension. The tolerances on partial dimensionsand total dimensions shall be interdependent.11.2 Addit ive P &ciple11.2.1 The most elementary way of establishingthis relationship shall be by means of adding thevalues of partial tolerances. Thus, assuming theseries of partial tolerances as II, 2-s ......... Tn themaximum deviation on total sum dimensions A,shall be calculated from the following equation:A 6 = zt J/2 x 1 Tl + Tr + .-....... Trl 1

REFERENCE

a----

11 B ORIENTATIONFIG~ 11 SETTI NG Our DEVIATIONFOR A LINE

6

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IS 6408 ( Part 2 ) I 1992

:-,---y-3+ a1L+____-A 1

12A POSITIONALFIG. 12 ERECTION

- qzfEq+12 6 ORIENTATION

DEVIATIONSFOR A.COMPONBNT

FIG. 13 Box PRINCIPLE ( DEVIATION OF FORM )11.2.2 Assuming total tolerance T, is equal to2As, it will always hold good. If it is required toselect a part tolerance on the basis of a given sum( total ) tolerance Z-s, the sum may be workedout from the following relationship:

Tr + T 9 +.- . . . . . . . 7. > T e11.2.3 This relationship between partial tolerancesand total tolerances is called the additive principle.This principle is also known as arithmeticalsummation principle.11.3 Summation of Tolerances11.3.1 It is a theoretical presumption that eachcomponent shall be erected within its allocatedmodular space with high degree of workmanshipin joints. But in practice, it is seldom achieved.11.3.1.1 The inaccuracy which occurs in size,squareness, bow, plumbness and position of eachcomponent and minimum joint width, if summedarithmetically, shall result into large space forjoints (see Fig. 14). For example, if minimum 5 mmis applied to five aspects of tolerances for twocomponents shall result into ( 5 ~5 ) + 5 +(5x5)= 55 mm space forjoint. This will be toolarge sum tolerance for a component.

12 CO-ORDINATE TOLERANCESApplication of the additive principle can lead tounrealistic values for small part tolerances orlarge sum tolerances. The principle can, therefore,be ~modified by introducing further toleranceswhich act differently on one and the same dimen-sion, the so-called collaterally regulating toleran-ces or co-ordinate tolerances. These details areexplained in 13 to 17.13 CHOICE OF TOLERANCE SlZE13.1 The size of tolerance shall be chosen on thebasis of the production method, jointing system,aesthetics and economy.13.2 The relationship of four dimension, namely,(a) controlling dimension, (b) basic dimension,(c) joint dimension, and (d) tolerances shalldepend on the connections between thecomponents.13.3 The tolerances on the basic dimensionsof a component are absorbed and equalized injoints between additive elements. For example oftolerance equalization Fig. 15 may be referredto

7

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Referring to the sizes shown in the Fig. thedistance between C and D lines:With large component and small joint:

With small component and large joint:

From above two equations:F max -Fmin- lrn8x lrnin 2 Trn

_- 1

I1;_ I1LA SIZE

4 -iIIIIIIIIII

l&D POSITI

or,Tf = i-i s 2 Trn

13.3.1 It can be seen that the given relationshipbetween two dimensions shall result in unevenjoints which perhaps may not absorb the toleranceon joint. It can also be seen that the positionaltolerance tends towards zero value due to highvalue of tolerance on component. This shall callfor high degree of site workmanship which maynot be practical.

I II II II II II II IILIII\

146EII 1 II II \ ;:bI I I I II I II II I II I: ::b

l&C BOW

FIG. 14

SQUARENESS

1LE PLUM8ASPECTS OF TOLBRANCB

III

I c

8

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IS 6408 ( art 2 ) : 1992

CONTROLLINGmm4 s l o N

-+$$OS,T,ON2x Lmi .1 TOLERANCE Tmi i! LIZ i I, L/2c, -I

t JOINT G h JOINT fc JOINT %MODULAR ZONE MO OULAR ZONE

L- Controlling dimension1 - Basic dimension componentF- Basic dimension joint

Tm - Position toleranceTl - Tolerance on componentTf - Tolerance on joint

FIG. 15 RELATIONSHIP BETWEBN CONTROLLING DIMENSIONS, COMPONENTS DIMBNSIONS,JOINT DIMENSIONS AND TOLBRANCBS14 TOLERANCE OF FLOOR 15 TOLERANCE ON BRICK SIZ ECOMPONENTS14.1 In linkage of the floor components the joint 15.1 Modular Sizeis assumed to be self-forming, which can be possi- 15.1.1 As shown in Fig. 16 modular standardble by grouting the joint from top without formwork and without mortar running right through. brickwork result in horizontal controlling dimen-sions that are divisible by 1 M ( = 100 mm ). InExamjle: order that the controlling dimension may be

The floor components comply with their con- observed during construction, bricks must betrolling dimension 1 200 mm. produced having suitable degree of accuracy.This means the floor components shall not be 15.1.2 The stretcher course with full bricks andwider than 1 200 mm. corresponding vertical joint, the marginal dimen-sion of work shall be determined as under:The basic dimension for the width is expressedas 1198f2mm. The controlling dimension = 200 mm

This limits the following dimensions for the !Maximum permissible joint = 16mmeomponent: Minimum permissible joint = 8mmMinimum permissible dimension 1 196 mmMaximum permissible dimension 1~200 mm 15.1.2.1 On the basis of above assumptions:Basic dimension 1 198 mm Upper marginal dimensions for the brickTolerance 4mm = 200 - 8 = 192 mm

9

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IS 6498 ( P a r t 2 ) : 1992Lo w e r marginal dimension for the brick

= 200 - 16 = 184 mmThe basic dimension of brick ( 192 + 184 )2= 188 mm andTolerance = 192 - 184 p: 8 mm or f 4 mm.

15.1.2.2 In order to achieve controlling dimensionof 200 mm, each brick must have limits for jointdimension with length of 188 -f 4 mm or f 2.1percent.15.1.3 In case, 200 mm controlling dimension isto be observed with nominal dimension of brick190 mm and tolerance of f 6 mm ( in accordance;hi;h IS lq77 : 19F6 ) (. see Note ) it results inmargmal dlmenslons with variationsf 3.1 percent.

Maximum brick length = 190 + 6 - 196 mmMinimum brick length = 190 - 6 = 184 mm.

This corresponds to joint of 4 mm minimum and16 mm maximum.

O,,,l,,,,sJ iiIIiWl

190 10N 0 MINAL

NOTE - As per IS 1077 : 1986, tolerance on 20 bricklengths is & 80 mm which gives an average toleranceof f 4 mm per brick length and hence a ma? toleranceoff 6 mm per brick can be permitted, provided thattolerance on any 20 bricks shall not exceed f 80 mm.

15.1.3.1 It can be seen from above that jointdimensions calculated are unrealistic and veryoften too large for achieving controlling dimensionsof 200 mm, even if it is calculated average of 20bricks.The deviations are equalized over larger lengthof brickwork, while adhering to the essentialdimensions for openings for doors and windows, itshall not be attained. Therefore, tolerances stipu-lations should be based on statistical basis.15.1.3.2 In order to achieve desired controllingdimensions, dimensions of each brick should havelimits as specified in 15.1.2~1 and 15.2.2.1.

inril_ 188 _I$_BASIC DIMENSION.

BASIC DIMENSION ANDMARGINAL DIMENSlOl;i$j~~ Al1 dimensions in millimetres.

FIG. 16 MODULAR BRICK TOLERANCES10

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15.2.2.2 In order to achieve controlling dimen-sion of 240 mm, the each brick must have limitsfor joint dimension with length of 228 f 4 mm orf 1.8 percent.

.15.2 N o n -a r o d u i a r Co ir v e n t i o n a l S i ze15.2.1 As shown in Fig. 17, the non-modularconventional brickwork result in horizontal con-trolling dimensiom that are divisible by 60 mm( 4 brick ). In order that the controlling dimen-sion may be observed during construction, bricksmust be produced having a suitable degree ofaccuracy. ,, 15.2.2 The stretcher,. course with full bricks andcorresponding vertical joints, the marginal dimen-sions of brick shall be determined as under:

The controlling dimension = 240 mmMaximum permissible joint p 16 mmMinimum permissible joint = 8mm

-15.2.2.1 On the basis of above assumptions:Upper marginal dimension for the brick

= 240 - 8 = 232 mmLower marginal dimension for the brick

=240- 16- 224mmThe basic dimension of brick232 + 224L: 2 = 228 mm, and

Tolerance = 232 - 224 = 8 mm or f 4 mm.

BASIC DIMENSION ANDMARGINAL DIMENSIONS

15.2.3 In case, 240 mm controlling dimension isto be observed with nominal dimension of brick230 mm and tolerance of f 3 percent and f 8percent, for class A and-class B types of bricks; itresults in the marginal dimensions.Class AMaximum brick length = 230 + 3 %= 237 mmMinimum brick length = 230 - 3 o/o

= 223 mm .This corresponds to a joint of 3 mm minimumand 17 mm maximum.

Class BMaximum brick length = 230 + 8 y0

= 248 mmMinimum brick length = 230 - 8 O/O

= 212 mmThis corresponds to a joint of 28 mm.

;L--yQNOMINAL DIMENSION

CLASS A -, 310CLASS B r 8O/o

All dimensions in millimetres.FIG. 17 STANDARP BRICK TOLERANCES

11

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IS 6408 ( Par t 2 ) : 199215.2.3.1 It can be seen from above that the jointdimensions calculated are unrealistic and large forstrict adherence to the controlling dimensions of240 mm. Therefore, tolerance specification shallhave to be prepared on a statistical basis.16 TOLERANCE ON COMP ONENT,DOORSET/ WINDOW SET WIDTH16.1 Building designers are not usually accom-plished to determine the tolerances for building

(

-m

-

Lx3M:lZM

1200 )

1189.5: l-5mm *

components, but nevertheless, the procedure for-calculation shall abreast t,hem to deliberate withmanufacturers who can render advise on manu-facturing tolerances for a product-positionaltolerances which are based on information gainedfrom site -assembly experiences.16.2 The process ~of calculating maximum andminimum size acceptable on site for a modularcomponent is illustrated in Fig. 18.

-9

1

t-

c

c

MODULAR SPACEassume 12 M wid thMODULAR SIZE

MINIMUM GA?g = 3+nm

POSITI ONAL TDLERANCep=3mm

MANUFACTURINGTOLERANCEt=3 mmMINIMUM GEDUCTION2g+p -9mm

MAXIMUM SIZE1200-g = 1191mm

MINIMUM SIZE1191-3 =1166 mm

MAXIMUM GAPgz3+3+l;5z7*5mm

MINIMUM GAPg= 5 (1200~-1191- 3)g=3 mmMANUFACTURINGDIMENSIONS TOBE SPECIFIEDAS 1169 ,- l-5 mm

All dimensions in millimetres.FIG. 18 DERIVATIONOP MANUFACTURESIZES

12

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IS 6408( Par t 2,) :1992-16.2.1 As a first step, select modular-component, and define the maximumtional and manufacturing tolerances.

size of thegap, posi-16.2.2 When the above have been settled, addup g + p + g and deduct it from modular size,which is the maximum size.16.2.3 Manufacturing tolerance deduced frommaximum size shall be a minimum size.16.2.4 Check the maximum gap = g + fi + t/2and also minimum gap = l/2 ( modular size -maximum - positional tolerance ), or differencebetween maximum size and minimum size.16.2.5 Lastly specify manfacturing dimensionas + l/2 minimum gap after adding l/2 minimumgap to minimum size.17 MODI FICATION OF THE ADDITIVEPR INCIP LE BY ADJUSTMENT17.1 When building elements are assembled bymeans of joints which may vary within definitelimits, one may within these limits adjust theposition of the element during assembly takinginto consideration the actual measurement of theelement. For a given joint tolerance, therefore, itis possible to set a large tolerance on the elementthan what is permitted by the additive principle.Such a modification implies, however, that it isnot possible to combine all measurements whichsatisfy the indicated tolerance required.17.2 Taking an example of a prefabricated orpartially prefabricated building having precastconcrete planks for floor component and the loadbearing precast beam/joist ( connection as shownin Fig. 19 ), the maximum permissible displace-ment of floor in relation to joint is f 10 mm.

n

17.2.1 If site concrete joint width of 60 mm ( .iX

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IS 6408 -( Part 2 ) t 199218 APPLICATION 0F CO-ORD~NATETOLERANCES 19 THE SQUARE ROOT RULE18.1 Co-ordinate tolerance are based on the 19.1 In practice, tolerance of the types T, , Tr , .Ts and T d are also calculated with this orincioles:..assumption that erection on a number of parallelprefabricated wall components shall be adjustedon site. Thus Ts is introduced with a value of10 mm, for determining the displacement of thesupport ( see Fig. 20 ). This shall be calculated_P. that isF =E- 2 + = 10that is 2.5 + 2.5 + -$ I 10therefore, T4 = 10 mm that is18.1.1 It can be noticed from above two princi-ples that the effect T I and T , is replaced by theeffect of T b, which offers more realistic value for C

g + q + _!A!& + [%-J ]I* = l@adoption in erection work. Therefore, T4 - 16;3 mm

PV GATEWAY(? n

BASIC ROOM DIMENSION e

TOLERANCEST1 = Thickness of wall componentT n = Placing of wall componentT 3 = Length of floor componentT 4 = Placing of floor componentTs = Room dimensionIv = Dimension of wall componentId = Dimension of floor component

FIG. 20 CO-ORDINATE OLE RANCES1.4

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$9.2 .The. calculation is based on followingassumptions:a) All the deviations in thickness, length andassembly have normal distribution,b) There are no systematic errors,c) It has some probability of error, andd) All deviations shall be independent.

19.3 It is seldom possible to have fulfilment ofabove assumptions in practice. Thus, error on Trwill be equal to Tr, Ts, and Ts.29 CONTROL OF MEASUREMENT29.1 In order to avoid ambiguity for controlmeasurement, it shall be necessary to satisfy thetolerance measurement precisely.29.2 It shall include the information on numbersof measurements, methods of production andmanufacturers constraints also.

.-IS 6408 ( Psl i t y+22 199221 SHRINKAGE,AND,CREEP21.1 The dimensions in various building productsare subjected to constant alteration due to changein temperature and moisture content, shrinkageand other deformation under conditions of use.This shall be clearly specified in order to avoidpossible rejection.21.2 The contributions from measuring instru-ments and methods adopted to determine the~deviation shall remain negligible if authorisedquality control department is involved for carryingout the tests on rendom samples.22 APPROVAL22.1 If the control measurements show deviationswith numerical values which are less than orequal to half the tolerance, the dimension shallbe adopted, otherwise it shall be rejected.22.2 Agreement on production and supply shallcontain clear understandings on consequencesarising from possible rejection.

ANNEX A( Clause 4.9 )

SERIES OF EXAMPLES OF THE PRECtSION CLASSESPrecision class PC 4 :

Precision class PC 5 :

Precision class PC 6 :

Steel sections;Timber moulding andprofiles of fine grained Precision class PC 7 :ashlar.Steel windows, door, fra-mes, trim; wood trimwindows and door sec-tions; components in finegrained ashlar; wall, ceil-ing, and floor surfaces.Prepared and fitted com-ponents ( such as frame-work, staircases, railings,floors, panels, cladding,gutters, rainpipes );Metal castings;Wood windows and doors; Precision class PC 8 :Built in furniture;Parquet flooring;Fine flooring, fine concretecomponents;Components of mediumgrained ashlar;Fine ceramics (e.g. pavingtiles, ceramic tile clad-dings);Floor coverings;

Installations ( such as gas,water and heating pipes).Forged and fabricatedframes and railings;Wrought components( such as floors, wallcoverings, steps );Planed boards, -planksbattens;Coarse flooring, Medium-grained concrete compo-nents;Ashlar facing;Plaster surfaces;Faces of joints.Unwrought components,carpentary ( such asframework joints, refters,unplanted boards, planks,battens );Components having finish-ed surfces of state degreeof accuracy ( such as con-crete facework compo-nents cast in metalforms );Surface of heavy concretedecks;

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156408(Part2):1992

Precision class PC 9 :

Precision class PC 10 :

Facing brickwork, Fair- Ta b l e 1 Ex a c t Va l u e s o f To le r a n c e G r a d e sface walling, Clay block-.work, masonry. ( Cluuse 4.9 )Components to be plaste- Tolerance grades for basic size ranges ( millimetres )red or clad ( such ascomponents cast inwooden forms, heavydecks and stairs in therough concrete );Components to be plaster-ed or clad ( such as walls,piers, decks stairs );Rough brickwork andblockwork.Components not requiringgreat accuracy ( such asfoundations );Walls, Room dimensions;Components not requiringgreat accuracy ( such asfoundations, retainingwalls ) unless an evencoarser degree of accu-_~

Class Up 10016"o 2

(1) (2) (3)PC 1 0.25 04PC 2 04 06PC 3 06 1-OPC 4 1.0 16PC 5 16 23PC 6 25 4PC 7 4 6PC 8 6 10PC 9 IO 16PC 10 16 25

250 1000 2500 OverGO 220 IOGO 10 000,

(4) (5) (6) (7)06 O% 10 1210 1.2 1.6 2016 20 25 3.225 32 40 5040 5.0 6.0 8.06 8 10 12

10 12 16 2816 20 25 3225 32 40 5040 50 60 80racy is sufficient.

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( Continu edfrom second cover )d) Dimensional co-ordination for building. DC12. HMSO Publication 1972.e) PC1 committee report on Tolerances for precast and prestressed concrete, PC1 Journal, Vol 30,No. 1, Jan/Feb. 1985.f) IS0 4464-1980 Tolerances in buildin_:: - relationship between the different types of deviations andtolerances used for specification. International Organization for Standardization.g) DS/R 1050-1982 Application of dimensional tolerances in building. Dansk Standardiseringsraad.h) DlN 18201-1984 Tolerances in buildings: terminology, principles, application and testing. Deust-sehes Institute for Normong.j) DIN 18201-1958 Dimensional tolerances in buildings: terminology, fundamental tolerances,application and testing. Deustsehes Institute for Normong.

For the purpose of deciding whether a particular requirernent of the standard is complied with, the finalvalue, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordancewith IS 2 : 1960 Rules for rounding off numerical values ( revised ). The number of significant placesretained in the rounded off value should be the same as that of the specified value in this standard.

Standard MarkThe use of the Standard Mark is governed by the provisions of the Bureau of IndianStandards Act, 1986 and the Rules and Regulations~made thereunder. The Standard Mark onproducts covered by an Indian Standard conveys the assurance that they have beenproduced to comply with the requirements of that standard under a well defined system ofinspection, tosting and quality control which is devised and supervised by BIS and operatedby the producer. Standard marked products are also continuously checked by BIS for con-formity to that standard as a further safeguard. Details of conditions under which a licencefor the use oft he Standard Mark may be granted to manufacturers or producers may beobtained from the Bureau of Indian Standards.

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Bweao of Indian StandardsBlS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification of goodsand attending to connected matters in the country.CopyrightBIS has the copyright of all its publications. No part of these publications may be lieproduced in anyform without the prior permission in writing of BIS. This does not preclude the free use, in the course ofimplementing the standard, of necessary details, such as symbols and sizes, type or grade designations,Enquiries relating to copyright be addressed to the Director ( Publications ), BIS.Revision of Indian StandardsIndian Standards are reviewed periodically and revised, when necessary and amendments, if any, areissued from time to time. Users of Indian Standards should ascertain that they are in possession of thelatest amendments or edition. Comments on this Indian Standard may be sent to BIS giving thefollowing reference:Dot : No. CED 10 ( 4295 )

Amendments Issued Since PublicationAmend No. Date of Issue Ted Affected

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