Dimensions Tolerance Specification

Concrete international / june 2009 33

By Cristian Masana

Dimensional Tolerance

Specificationthe iCH perspective on tolerances for reinforced concrete construction

A lmost everyone can agree that there will be deviations between the actual dimensions and locations of

concrete elements in a structure and the dimensions and locations indicated on the project drawings. The disagreements begin when limits on the acceptable amount of those deviations are established. The primary means by which these disagreements can be avoided is to clearly specify tolerances that can be met using reasonable care and construction methods and still meet the owner’s serviceability and aesthetic requirements.

By gathering data on jobs under construction, reviewing desired tolerances from a survey by the Architect Bureau Guild, consulting literature on acceptable tolerances, and using their own judgment, the Instituto del Cemento y del Hormigón de Chile (ICH) Committee on Technical Specifications for Contracts has developed ET 004-06, “Dimensional Tolerances in Reinforced Concrete Elements.”1 This specification provides a consistent set of tolerances for six different surface finish grades defined in the document. Before entering into a construction contract, contractors should inform the owner if, in their judgment, the tolerances can be met given the urgency of the project, the specified materials, and any other specific requirements. Most importantly, contractors should inform the owner if they believe the budget is not adequate to achieve the quality the owner expects.

SurfaCe finiSh graDeS anD ToleranCeSThe specification separates concrete finishes into six

different grades. Four grades are for general concrete construction, while the other two are specifically for slabs. The grades are defined in the specification as:■ G1: Architectural or exposed concrete—concrete

elements whose surface texture or finish will be permanently exposed to view without further treatment;

■ G2: Concrete for coating and painting—concrete elements whose surfaces will be provided with a rubbed finish or painted;

■ G3: Exposed concrete for public works—concrete elements whose surface finish is not altered and whose geometrical finish requirements are not as restrictive as those of G1;

■ G4: Raw concrete—concrete elements whose surfaces will be plastered or covered with another finish different from those considered in G2;

■ G5: Concrete for floors—the upper surface of a slab-on-ground or suspended slab that will be covered with carpet, wood, tile, or other material or will be exposed after polishing; and

An English translation of ICH Technical Specification ET 004-06 is available with the online version of

this article at www.concreteinternational.com

34 june 2009 / Concrete international

■ G6: Concrete for floors—the upper surface of a slab-on-ground or suspended slab that will not be covered or polished.Different grades may be specified

for different elements of the same structure, but they must be clearly indicated in the contract documents. G5 and G6 may be used for horizontal or inclined surfaces, such as ramps, but they are not applicable to industrial floors specified as flat floors.

The specified tolerances for the various grades of concrete finish are given in Tables 1 to 5. As shown in the tables, the tolerances vary depending on the length L, which is the distance between points where measurements are taken to determine compliance with the specified tolerance. These points are usually chosen arbitrarily and may be on any segment and in any direction along the plane of the evaluated surface. Choosing short lengths for local deformations and long lengths for long-wave deformations is suggested.

Predetermined cases with specific tolerance requirements may exist, such as aisles according to the Chilean General Building Code, and other tolerances may be specified to ensure compatibility with adjoining elements or other construction.

meaSuremenTThe owner or contractor may

measure elements where necessary, preferably by locating areas of concern by first performing a visual inspection. The measurements can be made using any tool or equipment with ±1 mm (±0.04 in.) accuracy, and the values are rounded to the nearest 1 mm (0.04 in.). The measurements are made with respect to an auxiliary plane parallel to the axis of the outlined element.

With one exception, tolerances are measured on concrete elements after the forms are stripped and before any supports are removed. That is, the tolerances consider only formwork system offsets or deformations—no

Table 1:Flatness tolerances For vertical surFaces

Surface finish grade

L ≤ 1.5 m(L ≤ 4.9 ft),*

mm (in.)

L ≤ 3 m(L ≤ 9.8 ft),*

mm (in.)

L ≤ 6 m(L ≤ 19.7 ft),*

mm (in.)

L > 6 m(L > 19.7 ft),*

mm (in.)

G1 4 (0.16) 6 (0.24) 10 (0.40) 25 (1.00)

G2 5 (0.20) 7 (0.28) 12 (0.48) 30 (1.20)

G3 7 (0.28) 12 (0.48) 18 (0.72) 30 (1.20)

G4 8 (0.32) 15 (0.60) 20 (0.80) 30 (1.20)* Length L is the distance between points where measurements are taken to determine

compliance with the specified tolerance.

Table 2:Flatness tolerances For soFFit surFaces beFore support removal


L ≤ 1.5 m(L ≤ 4.9 ft),*

mm (in.)

L ≤ 3 m(L ≤ 9.8 ft),*

mm (in.)

L ≤ 6 m(L ≤ 19.7 ft),*

mm (in.)

L > 6 m(L > 19.7 ft),*

mm (in.)

G1 4 (0.16) 6 (0.24) 10 (0.40) 15 (0.60)

G2 5 (0.20) 8 (0.32) 12 (0.48) 18 (0.72)

G3 6 (0.24) 10 (0.40) 15 (0.60) 20 (0.80)



Table 3:Flatness tolerances For soFFit surFaces aFter support removal


L ≤ 1.5 m(L ≤ 4.9 ft),*

mm (in.)

L ≤ 3 m(L ≤ 9.8 ft),*

mm (in.)

L ≤ 6 m(L ≤ 19.7 ft),*

mm (in.)

L > 6 m(L > 19.7 ft),*

mm (in.)

G1 6 (0.24) 10 (0.40) 15 (0.60) 20 (0.80)

G2 7 (0.28) 12 (0.48) 18 (0.72) 22 (0.88)

G3 8 (0.32) 14 (0.56) 20 (0.80) 25 (1.00)



Table 4:other tolerances


Variation from project axes,

mm (in.)

Door and window openings, mm (in.)

Rough seams on faces of elements,

mm (in.)

G1 5 (0.20)* 5 (0.20)* 3 (0.12)

G2 6 (0.24) 5 (0.20) 5 (0.20)

G3 10 (0.40) 5 (0.20) 5 (0.20)

G4 15 (0.60) 10 (0.40) 8 (0.32)* Other tolerances may be specified in the general building code or project documents.

Concrete international / june 2009 35

This is the last of a series of articles giving the Chilean perspective on various concrete construction issues. Previous articles include:■ Covarrubias, J.P., “Specification for Concrete

Cracking,” V. 29, No. 9, Sept. 2007, pp. 50-54;■ Masana, C., “Concrete Dumping Height Specifications,”

V. 30, No. 2, Feb. 2008, pp. 40-42; and■ Masana, C., “Formwork Removal Specifications,”

V. 30, No. 6, June 2008, pp. 38-40.

Table 5:Floor Flatness tolerances For suspended slabs and slabs-on-ground


L ≤ 1.5 m(L ≤ 4.9 ft),*

mm (in.)

L ≤ 3 m(L ≤ 9.8 ft),*

mm (in.)

L ≤ 6 m(L ≤ 19.7 ft),*

mm (in.)

L > 6 m(L > 19.7 ft),*

mm (in.)

Rough seams on same plane,

mm (in.)

G5 3 (0.12) 5 (0.20) 7 (0.28) 10 (0.40) 2 (0.08)

G6 4 (0.16) 7 (0.28) 10 (0.40) 15 (0.60) 3 (0.12)* Length L is the distance between points where measurements are taken to determine compliance with the specified tolerance.

structural deformations or strains are considered. Tolerances for vertical elements must be measured within 24 hours after removal of the formwork. For horizontal or inclined elements, tolerances are measured before removing the shoring system.

The exception to measuring tolerances before any shoring or supports are removed is the tolerances for soffit surfaces shown in Table 3. These are checked after formwork and shoring removal and therefore must include elastic deformations that are calculated and communicated by the structural engineer.

These tolerances are to be checked at least 30 days after support removal but before finishes are applied. Measurements after shoring removal must consider elastic deformations determined by the structural engineer.

nonComplianCeCorrections and sanctions, for the cases when construction

does not comply with the tolerances for the surface finish grade specified, should be indicated in the contract documents. These should also establish whether the owner is willing to accept surface repairs to meet tolerances and sanction the eventual rejection of the repair. Repair procedures to be used should be compatible with the structural and aesthetic requirements assigned to the element, and the owner or the owner’s representative may accept or reject a repair procedure proposed by the contractor.

In general, repairs are not accepted on G1 (architectural or exposed) surfaces. The only repair to these surfaces allowed is the trimming of raw seams of formwork joints without marking the concrete surface, unless the owner specifies otherwise. When deviations greater than those specified are found in elements specified as G1, the owner may order demolition of the element.

Repairs on G3 and G5 surfaces are acceptable if they are compatible with the structural and aesthetic requirements of the element. For G2, G4, G5, and G6, surface defects may be trimmed or filled to meet the specified tolerance, but the minimum cover thickness must be maintained.

Cristian Masana is a Civil engineer at iCH working as the technical secretary of the Performance Based specification Committee and as Chief of the Pavement Division. His research interests include design and construction specifications, time-dependent behavior of concrete, cracking, and durability of concrete structures.

uSeThe tolerance specification has been used on several

projects because it provides defined finish tolerances and avoids conflicts when the project is handed over to the owner. Its continued use is expected to help clarify the cost of specific tolerance requirements for projects and provide budget information for various quality levels.

references1. Especificacion Técnica ET 004-06, “Tolerancias Dimensionales

de Elementos de Hormigón Armado,” Instituto del Cemento y del

Hormigón de Chile, Santiago, Chile, Mar. 2006, 7 pp. (in Spanish)

Selected for reader interest by the editors.

COMMITTEE ON TECHNICAL SPECIFICATIONS FOR CONTRACTS

INSTITUTO DEL CEMENTO Y DEL HORMIGÓN DE CHILE

San Pío X No 2455 Providencia • Fono: (56-2) 232 6777 • Fax: (56-2) 233 9765 • Santiago Chile • E-mail: [email protected] www.ich.cl

TECHNICAL SPECIFICATION

ET 004-06:

DIMENSIONAL TOLERANCES IN

REINFORCED CONCRETE ELEMENTS

COMMITTEE ON TECHNICAL SPECIFICATIONS FOR CONTRACTS

COMMITTEE SCOPE The Committee gathers professionals related to the construction area who have shared their experience and knowledge to prepare this Technical Specification (ET) based on concrete behavior and aimed at reducing eventual disputes on construction sites.

Representatives of the companies in the Committee: Company Representative Company Representative AICE 3 Mr. Fernando Yañez DRS 1 Mrs. Ana María Butrón AOA 1 Mr. Luis Izquierdo Icafal 2 Mr. Raúl Salas ARA 3 Mr. Mario Muñoz Metro S.A. 1 Mr. Carlos Mercado Bechtel 1-3 Mr. Bernhard Paul Minmetal 1-3 Mr. Fernando Durán Besalco 2 Mr. Manuel Macaya Minvu 1 Mr. Camilo Sánchez Brotec 2 Mr. Leonardo Vildósola MOP 1 Mr. Rogelio Navarrete Constructora BI 2 Mr. Luis H. Bravo PUC 4 Mr. Carlos Videla Cade Idepe 1-3 Mr. Eric Woolvett Salfacorp 2 Mr. Carlos Fernández Codelco Chile 1 Mr. Felipe Urrutia Sigdo Koppers 2 Mr. Oscar Guarda Cruz y Dávila 1 Mr. Jorge Bravo Tecsa 2 Mr. Alejandro Albertz DLP 2 Mr. Javier Darraidou Vial y Vives 2 Mr. Manuel José Navarro Members of the Formwork and Dimensional Tolerances Committee: Renato Vargas ICH Technical Secretary ([email protected]) Jorge Montegu Committee Advisor

NAME INSTITUTION NAME INSTITUTION Luis Izquierdo AOA 1 Juan Horstman Moldajes Peri 5 Arturo Holmgren Cementos Polpaico 5 Jorge Ignacio Prieto Moldajes Peri 5 Yuri Tomicic Cementos Polpaico 5 Rodrigo Núñez Moldajes RMD 4 Javier Darraidou DLP 2 René Guerra Resmat - Dictuc 5 Cristian Masana ICH Oscar Guarda Sigdo Koppers 2 Federico Delfín Idiem U.de Chile 4 Hugo Barrera Usach 4 Oscar Flores Inarco 2 Rodrigo Mujica VMB Ingenieros Estructurales 3 Gabriel Muñoz Moldajes Peri 5 1.- Owner or his representative (Concrete Construction Inspector & Architects) 2.- Contractor 3.- Designer 4.- University 5.- Industrialist

ET 004-06: Dimensional Tolerances in Reinforced Concrete Elements

1

ET 004-06: Dimensional Tolerances in Reinforced Concrete Elements CONTENTS COMMENTS

I. GENERAL I.1. Objective: The aim of this Technical Specification (ET) is to set dimensional tolerances for reinforced concrete elements in order to include them in the construction contract.

I.2. Terminology: The following terms are used in this ET:

I.2.1. Finishing Grades: different types of concrete surface finishing and associated permissible dimensional tolerances.

I.2.2 Architectural or exposed concrete, Grade 1: concrete elements, whose surface texture or finishing will be permanently exposed to view, without further treatment.

I.2.3. Concrete for coating and painting, Grade 2: concrete elements that shall be provided with a rubbed finish or painted as finishing.

I.2.4. Exposed concrete for public works, Grade 3: concrete elements whose surface finishing is not changed in form and whose geometrical finishing requirements are lower than those of Grade 1 (for architectural or exposed concrete).

I.2.5. Raw concrete, Grade 4: concrete elements whose surfaces shall be plastered or shall be covered with other finishing, different from those considered in Grade 2.

I.2.6 Concrete for floors, Grade 5: the upper part of a slab-on-ground or concrete floor that will be covered with carpeting, wood, tiles or other material, or will be exposed once polished.

C.I.1.a) Deviations from values and lines indicated in drawings are accepted in construction, but limits to those deviations should be established. C.I.1.b) Contractor should inform the owner in advance (before submitting a construction contract) that, in his judgment, such tolerances are impossible to obtain. C.I.2.1 Normal qualities required in actual jobs.

C.I.2.6.a. Surfaces may be horizontal or inclined (ramps). C.I.2.6.b. The polished finishing may be manual or mechanical according to the project specifications.


2

I.2.7. Concrete for floors, Grade 6: the upper part of a slab-on-ground or concrete floor without recovering or polishing.

I.2.8. Permissible deviation: the allowable difference between a particular value and the reference value. Deviations may be positive (+) or negative (–). In this document deviations are considered symmetrical. Under special conditions, deviations may be asymmetrical.

I.2.9. Tolerance: the absolute value of sum of permissible deviations.

I.2.10. Flatness: the difference of distances between a reference theoretical plane (vertical, horizontal or inclined) and the actual surface of the element. Verticality: Flatness of a vertical element. Horizontality: Flatness of a horizontal element.

I.2.11. Rough seams: clots or scales left on the element surface at the joints of formwork plates, between wall sections, or arising during the surface finishing of slabs or concrete floors. In all cases, these are measured on a direction perpendicular to a theoretical surface parallel to the element’s face.

I.3. Scope

I.3.1. Dimensional tolerance values defined in this ET were set considering the maximum permissible limits.

I.3.2. Maximum permissible values are measured on stripped concrete elements without recovering, and considering only formwork system deformations. No structural deformations or strains are considered.

C.I.2.8. Permissible deviations shall depend on the Grade previously chosen by the owner. C.I.3.1. Finishing Grades have been set for construction procedures consistent with actual finishing techniques.

II. TECHNICAL SPECIFICATION II.1 MINIMUM REQUIREMENTS FOR DIMENSIONAL TOLERANCES


3

II.1.1 Maximum permissible deviations shall be established by the project engineer according to the Grade chosen and must be clearly specified in the project’s documents. II.1.2. Deviation of vertical elements shall be measured 24 hours after formwork removal. II.1.3. For horizontal or inclined elements, deviations will be those measured before removing the bracing system. Measurements after bracing removal must consider elastic deviations designed by the structural engineer. II.1.4. The following tables show the maximum permissible dimensional tolerances for different finishing grades of reinforced concrete: II.1.5. MAXIMUM VALUES OF DEFORMATION ON SURFACE FINISHING a) FLATNESS ON VERTICAL

SURFACES Height L≤ 1.5 m L≤ 3 m L≤ 6 m L> 6 m Grade Max.,

mm ±

Max., mm

±

Max., mm

±

Max., mm

± G1 4 6 10 25 G2 5 7 12 30 G3 7 12 18 30 G4 8 15 20 30

C.II.1.1.a) There are six Grades for the maximum permissible tolerances. C.II.1.1.b) The owner may choose a different Grade, even though this may not agree with any type described in this ET. Example: Concrete for public works may be specified as Grade 1. C.II.1.1.c) Required Grades may be different for different elements of the same construction, if so indicated.

C.II.1.3. This instruction does not exempt the contractor from complying with the specified formwork removal conditions.

C.II.1.4. Tables were constructed according to document DTE TM3. C.II.1.5.i. These dimensional tolerances are established for typical cases. Special cases using different requirements must be specified by the owner. These requirements must be clearly written in the project drawings and technical specifications. C.II.1.5.ii. Terminology used to define Grades is: G1 = Grade 1: Architectural or exposed concrete. G2 = Grade 2: Concrete for coating and painting. G3 = Grade 3: Exposed concrete for public works. G4 = Grade 4: Raw concrete. G5 = Grade 5: Concrete for floors which will be recovered or polished. G6 = Grade 6: Concrete for floors, without recovering or polishing.


4

b) FLATNESS ON HORIZONTAL SURFACES (ceilings) OF FORMWORK AFTER CASTING

Length L≤ 1.5 m L≤ 3 m L≤ 6 m L> 6 m Grade Max.,

mm ±

Max., mm

±

Max., mm

±

Max., mm

± G1 4 6 10 15 G2 5 8 12 18 G3 6 10 15 20 G4 8 14 20 25

c) FLATNESS ON HORIZONTAL SURFACES (ceilings) AFTER FORMWORK REMOVAL

Length L≤ 1.5 m L≤ 3 m L≤ 6 m L> 6 m Grade Max.,

mm ±

Max., mm

±

Max., mm

±

Max., mm

± G1 6 10 15 20 G2 7 12 18 22 G3 8 14 20 25 G4 9 17 25 30

d) OTHER DEVIATIONS Variations from

the project axes door and window

openings

Rough seams on element’s

face Grade Max., mm

± Max., mm

± Max., mm

± G1 5(1) 5(2) 3 G2 6 5 5 G3 10 5 5 G4 15 10 8

e) Floors

L≤ 1.5 m L≤ 3 m

L≤ 6 m

L> 6 m

Rough seams

on same plane

Grade Max., mm

±

Max., mm

±

Max., mm

±

Max., mm

±

Max., mm

± To be recovered or polished

G5 3 5 7 10 2 Without recovering and without polishing

G6 4 7 10 15 3

C.II.1.5.iii L is the total or partial reference length, arbitrarily chosen, on any section or direction of the plane. It is suggested choosing short lengths for local deformations, and long lengths for long-wave deformations. C.II.1.5.c) Table II.1.5.c refers to deformation during construction, including element deformation, without overloads, measured at the raw construction stage and at least 30 days after formwork removal. C.II.1.5.d).i. Predetermined cases with specific requirements may exist. Ex.: aisles according to the Chilean General Building Code. C.II.1.5.d).ii. Consider the option “measurement agreement.” This maximum deviation refers to that specified in the project drawings. If fitting elements or different construction systems are used, other tolerances may be specified. C.II.1.5.e) Grade 5 (G5) and Grade 6 (G6) may be used for horizontal or inclined surfaces (ramps). These Grades are not applicable to industrial floors specified as flat floors. See TDS 004-06.


5

II.2.CHECKING TOLERANCE STANDARDS II.2.1. The owner or contractor may measure elements where necessary, preferably by visual inspection in areas where dimensional problems are observed. II.2.2. Measurements must be made using any tool or equipment with ±1 mm accuracy. II.2.3. Measurements will be rounded to the nearest millimeter. II.2.4 Measurements will be made with respect to an auxiliary plane parallel to the outlined element axis. II.2.5. Maximum permissible tolerances shall be complied with throughout the total section as well as in any partial section.

C.II.2.1. The contract or protocol between the parties shall stipulate who will effect measurements, which areas or job sections are to be measured, the amount of measurements and the time when these shall be carried out. C.II.2.2. Recommended tools and equipments for these measurements are mentioned in document TDS 004-06 C.II.2.4 Tolerances of the outlined axis are not covered by this technical specification. It is suggested that these tolerances be specified in a separate chapter of the project’s specifications.

II.3 NONCOMPLIANCE II.3.1. In case contractor does not comply with maximum permissible tolerances for the grade of the specified surface, measurements, and corrections and sanctions shall be indicated in the contract documents. II.3.2. Noncompliance with maximum permissible tolerances, in intermediate or final batches, its correction, or repairing actions, will be the contractor’s responsibility. II.4. REPAIR OF SURFACE FINISHING II.4.1. The contract should establish whether the owner is willing to accept surface repairs to meet permissible tolerances, and sanction the eventual rejection of the repair. II.4.2. The owner or his representative may accept or reject a repair procedure proposed by the

C.II.3.1. Actions to be carried out will depend on the type and location of the element in the structure.

C.II.3.2. Noncompliance with dimensional tolerances does not exempt the contractor from his responsibility over the effects that repairs or corrections may cause on the structure stability or durability.


6

contractor. II.4.3. Repair procedures to be used must be compatible with the structural and aesthetic requirements of the element. II.4.4 General criteria for different finishing Grades: II.4.4.1. Finishing on architectural or exposed concrete: Normally repairs will not be accepted on such surfaces. Nevertheless, if deviations are greater than the specified tolerances for exposed concrete Grades, repairs will be carried out as follows: II.4.4.1.a) Grade 1: Only trimming raw seams of formwork joints without marking the concrete surface will be accepted, unless the owner specifies otherwise. II.4.4.1.b) When deviations and surface damage greater than those specified are found in elements specified Grade 1, the owner may order demolishing the element. II.4.4.1.c) Deviations greater than specified and damage on the element surface of Grade 3 and Grade 5 may accept minor repairs, compatible with the structural and aesthetic requirement of the element. II.4.4.2. Concrete surface finishing with recovering: If measured deviations are greater than those specified for Grades not considered exposed concrete, such as Grade 2, Grade 4, Grade 5 and Grade 6, surface defects may be trimmed or filled in order to meet the specified tolerance. This by no means allows reducing the minimum specified recovering thickness.

C.II.4.4.1.c) Special aesthetic requirements for finishing grades G3 or G5 must be included in the contract specifications. C. II.4.4.2. Concrete Grade 4 and Grade 6 are not considered exposed concrete.


7

III. FOLLOWING CONTRACTOR’S OWN CASTING PROCEDURE DOES NOT APPLY

IV. LACK OF CONTRACTOR’S OWN CASTING PROCEDURE DOES NOT APPLY

Documents

Dimensions Tolerance Specification