## TCVN 9261:2012 ISO 1803:1997 Building construction – Tolerances-Expression of dimensional accuracy- Principles and terminology

**Foreword**

TCVN 9261:2012 is completely equivalent to ISO 1803:1997.

TCVN 9261:2012 was converted from TCXD 252:2001 (ISO 1803:1997) in accordance with clause 1, Article 69 of the Law on Standards and Technical Regulations and point a), clause 1, Article 7 of the Government’s Decree No. 127/2007/ND-CP dated August 1, 2007 detailing the implementation of a number of articles of the Law on Standards and Technical Regulations.

TCVN 9261:2012 was compiled by the Institute of Architecture, Urban and Rural Planning, proposed by the Ministry of Construction, appraised by the Directorate for Standards, Metrology and Quality, and announced by the Ministry of Science and Technology.

**1. Scope**

**1.1.** This standard specifies the principles for expressing dimensional deviations in construction and defines the basic terms and definitions related to the assessment, technical requirements and accuracy inspection.

**1.2.** This standard applies to the manufacture of components (standardized or purpose-built), during the preparation, assembly of components and building structures.

NOTE: Equivalent terms in English and French are presented in Annex A.

**2. General provisions**

During construction, when there are requirements for achieving accuracy and fit, it is necessary to examine in detail the construction technology, functionality and aesthetic requirements of the building as well as the cost of erection, purpose of use, interchangeability of components during service life.

Building on-site, a large-sized object (like a house) involves assembling components of different sizes through a series of measurement and positioning operations which can lead to deviations from the design dimensions and shapes (incurred deviations). In addition, there are unavoidable dimensional changes due to movement, changes in material dimensions under the influence of environmental changes, loads and other conditions (inherent deviations).

This standard is used to:

a) Evaluate and apply in design taking into account the anticipated dimensional deviations;

b) Compare the dimensional requirements of joints with the expected dimensional deviations so that the joints meet the functional requirements;

c) Clearly specify the dimensional accuracy requirements in the design for all stages of construction;

d) Check dimensions and verify the conformity of shapes, sizes of components manufactured on-site and in the building throughout the manufacturing, installation and erection processes.

In practice, dimensional variations occur in all manufacturing and measurement processes. Inaccuracies will appear at each stage of the construction process, leading to deviations (manufacturing deviations, installation and erection deviations) from the desired dimensions (target sizes – see Figure 1).

Thus, for the actual performance of the building to meet the requirements or achieve the necessary functionality, dimensional deviations must be taken into account using probabilistic methods where appropriate. The basic design requirements will set limits for deviations (permitted deviations) on which the target sizes must be based for conformity checking (see Figure 2). This process should not only be carried out at the end of the stage (in many cases it may be too late to correct errors) but should be carried out at each stage during the manufacturing, installation and erection processes.

The dimensions of the building and components will always change according to physical conditions such as temperature and humidity. Therefore, it is necessary to clearly state the standard physical conditions, time and required accuracy of the measurement to which the target sizes and permitted deviations apply.

**Figure 1 – Illustration of manufacturing, installation, erection deviations combining to produce the final deviation in the completed building**

**Figure 2 – Target, actual performance and the fit between performance and target**

**3. Terms and definitions**

The following terms and definitions are the basic terms describing dimensions in technical requirements and measurement to meet building construction requirements.

**3.1. Dimension**

The extent in a given direction, straight line or angle.

NOTE: The extent in this concept is unquantified.

**3.2. Size**

The magnitude of a dimension quantified in a specified unit.

**3.3. Target size**

The reference size used in design and practice, representing the desired size and related deviations, the deviations being considered ideal if they have a value of zero.

NOTE:

1) The term “construction size” is the target size used in manufacture to achieve the target size specified in the drawings and taking into account systematic deviations occurring in the production process used or inherent deviations of the materials used;

2) If it is not necessary to specify a target size then any size can be chosen as the reference size related to the deviations;

3) In some countries and some fields (e.g. mechanical engineering), the term “nominal size” is used as the reference size. In construction, this term should only be used to refer to the approximate magnitude of a dimension.

**3.4. Target angle**

The reference angle used in design and in practice, representing the desired angle with related deviations; these deviations are considered ideal if they have a value of zero.

**3.5. Actual size**

The size whose value is determined by measurement.

NOTE: Where necessary, the measurement shall be corrected for the physical conditions during measurement.

**3.6. Upper limit of size**

The largest permissible actual size.

**3.7. Lower limit of size**

The smallest permissible actual size.

**3.8. Deviation**

The difference between the actual size and the corresponding target size.

NOTE: In some cases, it is necessary to distinguish deviations caused by the physical environment, such as temperature, shrinkage, magnetism or loading (inherent deviations) and deviations due to variations in manufacture, setting out and erection (incurred deviations).

**3.9. Upper permitted deviation**

The difference between the upper limit of size and the corresponding target size.

**3.10. Lower permitted deviation**

The difference between the lower limit of size and the corresponding target size.

**3.11. Tolerance**

The difference between the upper and lower limits of size.

NOTE:

1) Tolerance is an absolute value without sign;

2) In building construction, tolerance is often expressed as “± permitted deviation” and should therefore be understood as the tolerance value (see Figure 3);

3) An example of the relationship between the terms in this standard is shown in Figure 3.

**Figure 3 – Example of the relationship between important terms**

**4. Terms and definitions related to dimensional variations**

The following terms are used to express the relationship between actual size and target size.

NOTE:

1) Deviations of profile and shape are expressed by the difference between three-dimensional coordinates and target three-dimensional coordinates.

2) The measurement method for these terms is specified in TCVN 9262-1:2012.

**4.1. Length deviation**

The difference between the actual length and the corresponding target length.

**4.2. Angular deviation**

The difference between the actual angle and the corresponding target angle.

NOTE:

1) Deviations can be calculated in “gon”, degrees (°) or perpendicular displacement over a given length. Where “gon” is the unit of angular measurement calculated on a decimal basis.

2) In particular, the angular deviation is the deviation of the angle formed between the actual line and the given reference line, such as the meridian, X or N axis, horizontal line and vertical line (plumb line).

**4.3. Profile deviation of a line**

Diagram of the difference between the actual positions of a set of specified points on a line and the points on the corresponding target line.

**4.3.1. Straightness deviation of a line**

Diagram of the difference between the actual positions of a set of specified points on a line and points on a straight line passing through 2 specified points lying on that straight line.

**4.4. Shape deviation of a surface**

Diagram of the difference between the actual positions of a set of specified points on a surface and the points on the corresponding target surface.

**4.4.1. Flatness deviation of a surface**

Diagram of the difference between the actual positions of a set of specified points on a surface and the points on the corresponding plane.

NOTE: Flatness deviation is usually determined along straight lines of specified length, arranged at specified or random positions.

**4.4.2. Skewness**

The difference between the actual position of a corner point or a point lying on the outer edge of a surface and the corresponding target position on the plane passing through three different points of the corner or through the points lying on the outer edge of that surface.

**4.5. Position deviation of a point**

The difference between the actual position of a point and the corresponding target position relative to a specified datum.

NOTE: Position deviation is usually measured separately in both the horizontal and vertical planes.

**4.6. Position deviation of a line**

The difference in the actual position of specified points on a line and the points at the corresponding target positions relative to a specified datum.

**4.7. Verticality deviation**

The horizontal difference between a specified point on a straight line or on a plane intended to be vertical and the corresponding target point on a vertical reference line or reference plane (See note 4.2).

**4.8. Horizontality deviation**

The vertical difference between a specified point on a straight line or a plane intended to be horizontal and the corresponding target point on a horizontal reference line or on a horizontal reference plane (See note 4.2).

**4.9. Joint alignment deviation**

The difference in relative elevation or position at the joint of adjoining components intended to be flush with each other.

**4.10. Shape deviation**

The difference between the actual shape of an object and the corresponding target shape.

NOTE: The actual shape of an object lies between two envelopes representing the smallest and largest permissible objects.

**Annex A (Normative) List of terms in Vietnamese – English – French**

Term | Vietnamese | English | French |

3.1 | Kích thước | Dimension | Dimension |

3.2 | Kích cỡ | Size | Dimension (valeur numérique) |

3.3 | Kích cỡ chuẩn | Target size | Dimension recherché |

3.4 | Góc chuẩn | Target angle | Angle recherché |

3.5 | Kích cỡ thực | Actual size | Dimension réelle |

3.6 | Giới hạn trên của kích cỡ | Upper limit size | Dimension limite supérieure |

3.7 | Giới hạn dưới của kích cỡ | Lower limit of size | Dimension limite inférieure |

3.8 | Độ sai lệch (sai số) | Deviation | Écart |

3.9 | Độ sai lệch trên cho phép | Upper permitted deviation | Écart supérieure admissble |

3.10 | Độ sai lệch dưới cho phép | Lower permitted deviation | Écart inférieure admissble |

3.11 | Dung sai | Tolerance | Tolérance |

4.1 | Độ sai lệch theo chiều dài | Length deviation | Écart de longueur |

4.2 | Độ sai lệch góc | Angular deviation | Écart angulaire |

4.3 | Sai lệch về biên diện của một đường | Profile deviation of line | Écart de forme d’une ligne |

4.3.1 | Sai lệch về độ thẳng của một đường | Straightness deviation of line | Écart de rectitude d’une ligne |

4.4 | Độ sai lệch về hình dáng của một mặt | Shape deviation of a surface | Écart de forme d’une surface |

4.4.1 | Độ sai lệch về độ phẳng của một mặt | Flatness deviation of a surface | Écart de planéité d’une surface |

4.4.2 | Độ vênh | Skewness | Voile |

4.5 | Độ sai lệch về vị trí của một điểm | Position deviation of a point | Écart ponctuel |

4.6 | Độ sai lệch về vị trí của đường | Position deviation of a line | Écart de position d’une ligne |

4.7 | Độ sai lệch so với phương thẳng đứng | Verticallity deviation | Écart d áplomb |

4.8 | Độ sai lệch so với phương nằm ngang | Horizontality deviation | Écart de niveau |

4.9 | Độ sai lệch về mối nối | Joint alignment deviation | Desaffleurement |

4.10 | Độ sai lệch về hình dáng | Shape deviation | Écartde forme |

**Annex B (Informative) Bibliography**

TCVN 9254-1 : 2012, *Buildings and civil engineering works – Vocabulary – Part 1: General terms;*

TCVN 9259-1 : 2012, *Building construction tolerances – Part 1 – Basic principles for evaluation and specification;*

TCVN 9259-8 : 2012, *Building construction tolerances – Part 8: Dimensional inspection and verification of construction;*

TCVN 9262-1: 2012, *Measurement in building construction – Part 1: Methods and instruments;*

TCVN 9262-2: 2012, *Measurement in building construction – Part 2: Measurement positions;*

ISO 6707-2 : 1993, *Building and civil engineering – Vocabulary- Part 2: Contract terms.*