Foreword

TCVN 9262-2:2012 is fully equivalent to ISO 7976-2:1989.

TCVN 9262-2:2012 has been converted from TCXD 210:1998 (ISO 7976-2:1989) according to the provisions in 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 some articles of the Law on Standards and Technical Regulations.

The TCVN 9262 series with the general title “Tolerances for Building – Measuring Methods for Buildings and Building Products” comprises 2 parts as follows:

– TCVN 9262-1:2012, Part 1: Measuring methods and instruments

– TCVN 9262-2:2012, Part 2: Position of measuring points.

TCVN 9262-2:2012 has been drafted by the Institute of Architecture, Urban and Rural Planning, proposed by the Ministry of Construction, appraised by the General Department of Standards, Metrology and Quality, and announced by the Ministry of Science and Technology.

1. Scope

This standard provides guidance on determining the position of points to be measured when carrying out measurements on buildings and prefabricated components. These positions are used for checking, acceptance measurements and measurements for the collection of accurate data. This standard is divided into two parts:

– Part one specifies the position of measuring points for measurements that can be carried out both in the factory and on the construction site;

– Part two specifies the position of measuring points for measurements that are only carried out at the construction site.

NOTE: Construction products such as fiberglass and similar soft materials are not covered by this standard.

2. Normative references

The following referenced documents are indispensable for the application of this standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

TCVN 9262-1:2012^[1], Tolerances for building – Measuring methods for buildings and building products – Part 1: Measuring methods and instruments;

ISO 4463, Measurement methods for building – Setting-out and measurement.

3. General provisions

During acceptance measurements and measurements for the collection of accurate data, suitable positions of measuring points will be found. Measurements may be from 1 point, towards 1 point or between points.

The positions of the measuring points shall be predetermined in a summary table or similar documents, otherwise the measuring points shall be taken 100 mm from corner points or edges (see Figure 1). The following examples will illustrate some of the most common cases. If this is not possible, the positions of the measuring points shall be recorded in the field diary.

Figure 1 – Determining the position of measuring points

The number of positions of measuring points under the following conditions should be calculated to be minimal, and additional measurements may also be carried out to more accurately reflect the dimensions to be measured.

Details shall be measured in the state as they are used in practice, if this cannot be done then measurements in the specific conditions at that time must be accepted.

Where permitted, products should be measured at the time they are being prepared for delivery.

If there are no special requirements, components should not be measured while still in the formwork or during assembly.

On site, construction deviations (see Clause 5) can be determined according to the site coordinate system, according to the design reference system or the height during assembly, according to the vertical or according to other components.

4. Position of measuring points carried out in the factory and on site

4.1. Dimensions of components

4.1.1. Length and width

On each face of the prefabricated component, 3 lengths (L₁ to L₃) and 3 widths (W1 to W3) shall be measured as described in Figure 2. If the specified width is less than 1.2 m then L2 need not be measured. If the specified length is less than 1.2 m then W2 need not be measured.

Figure 2 – Length and width to be measured

4.1.2. Nominal width

The nominal width of prefabricated components shall always be measured.

Figure 3 describes two measuring points applicable to components with a fixed bottom plate.

For components with a fixed top or wall plate, two measuring points are described in Figure 4. Components manufactured as parts shall only be measured after those parts have been tightly assembled together.

Figure 3 – Two measuring points for components with a fixed bottom plate

Figure 4 – Two measuring points for components with a fixed top or wall plate

4.1.3. Thickness or (height) of cross-section

Each component to be measured will have 8 measurements of thickness or height of cross-section.

Figure 5 describes the measuring points for components with a rectangular cross-section. Positions with a specified width of less than 1.2 m do not need to be measured at points T₄ and T₈. At positions with a specified length of less than 1.2 m, measurements at points T₂ and T₆ are not necessary.

Figure 5 – Measuring points for components with a rectangular cross-section

Figure 6 describes the measuring points for components with a non-rectangular cross-section.

Figure 6 – Measuring points for components with a non-rectangular cross-section

Figure 7 describes the points for measuring the thickness of cast-in-situ concrete beams.

Figure 7 – Points for measuring the thickness of cast-in-situ concrete beams

4.1.4. Thickness of bricks, wall blocks or cast-in-situ concrete walls

Figure 8 describes the points for measuring the thickness of walls with a length of less than 3 m.

Figure 9 describes the points for measuring the thickness of walls with a length greater than 3 m. The intermediate measuring points at the top should be evenly spaced (but not more than 3 m apart) from the 2 points at the 2 ends of the wall.

Figure 8 – Description of points for measuring the thickness of walls less than 3 m in length

Figure 9 – Measuring points for wall thickness with a length greater than 3 m

4.1.5 Measurement of dimensions of components with non-rectangular cross-section.

When prefabricated components cast in-situ have a design cross-sectional dimension that varies, 2 additional measurements shall be made as described in Figure 10.

Figure 10 – Description of additional measurements for components with non-rectangular cross-section

4.2. Squareness of components

4.2.1. Angular deviation

The angular deviation is determined at all 4 corners of the component as described in Figure 11 for all cases.

Figure 11 – Determining the deviation at 4 corners of the component

To measure the angular deviation, 2 reference points R₁ and R₂ are created to form a reference line and 2 measuring points M₁ and M₂ are required (see Figure 12).

Figure 12 – Determining the position of two reference points R and measuring points M

The height of the column of a building story should be measured at the top, middle and bottom as described in Figure 13.

Figure 13 – Measuring the height of a column

Both horizontal and vertical squareness must be measured (see Figure 14).

Figure 14 – Measuring squareness in both horizontal and vertical directions

For prefabricated components with a non-rectangular cross-section such as beams with edges, the angle should be measured along the two vertical surfaces (See Figures 11 and 15).

Figure 15 – Measuring the angle along two vertical surfaces

If the squareness is determined by diagonal measurement, the measuring points for each measurement will be the 2 corresponding corner points as described in Figure 16.

Figure 16 – Measuring points when determining squareness by diagonal measurement

NOTE: In the case of diagonal measurement, the corner points must be used if the angles cannot be accurately determined.

4.2.2. Parallelism

The deviation from parallelism is determined using the measuring points as in 4.1.1. The measured dimensions are described in Figure 17 (See also Figure 2).

Figure 17 – Determining the deviation from parallelism

4.3. Straightness and curvature of components

4.3.1. Straightness

On each edge of a prefabricated component (For example: floor, wall or beam) with dimensions less than 3 m, an array of 5 evenly spaced measuring points can be arranged (See Figure 18).

Figure 18 – Position of 5 measuring points when measuring straightness of components less than 3 m

For components with a length greater than 3 m, an additional measuring point must be taken for every 1 m in length.

When measurements need to be taken at the edge cross-section of the component (local straightness), at least 3 or preferably 5 evenly spaced measuring points are required (0.5 m apart). (See Figure 19).

Figure 19 – Measuring straightness of components greater than 3 m

4.3.2. Calculated curvature

A series of measurements to determine the calculated curvature are carried out on the underside when the width of the component does not exceed 1.2 m. In addition, measurements can be taken at points as described in Figure 20.

Components with a non-rectangular cross-section, for example: T-shaped or double T beams, when determining the calculated curvature, measurements are also taken at points on the two sides (edges) as described in Figure 21.

Figure 20 – Measuring points for determining the curvature of components with a rectangular cross-section

Figure 21 – Measuring points for determining the curvature of components with a non-rectangular cross-section

4.4. Flatness and warping of components

4.4.1. Measuring principles

The general measuring principles are presented in 4.4.1 of TCVN 9262-1:2012. The measuring methods follow the principles described in 4.4.2 to 4.4.5 and these measuring points correspond to the provisions of TCVN 9262-1:2012.

4.4.2. Overall flatness

On each face of the prefabricated component, the measuring points are determined as described in Figure 22.

The number of measuring points depends on the dimensions of the component, at least 9 measuring points are required and the distance between points shall not exceed 1 m.

Figure 22 – Determining measuring points when measuring overall flatness

4.4.3. Local flatness measurement

On the surface to be measured for local flatness, one or more arrays of measuring points can be taken. The maximum length of an array is 2 m and the maximum distance between measuring points is 0.5 m.

The position of this array can be taken arbitrarily but note that they must match the edge of the component. Each measuring array consists of 5 evenly spaced measuring points according to the measuring range as described in Figure 23.

4.4.4. Warping

To determine warping, depending on the measuring method, 4 or 5 measuring points are required: either 4 points at 4 corners or those 4 points and an additional point at the intersection of the 2 diagonals (see Figure 24).

Figure 23 – Measuring point arrays

Figure 24 – Measuring points for determining warping

5. Position of measuring points carried out on site

In this section, it is considered that there are suitable reference systems on site or at the assembly location during measurement, such as auxiliary points or lines, grids and reference markers, and of course these reference systems will also be checked according to the provisions in ISO 4463.

5.1. Position in the horizontal plane

TCVN 9262-1:2012 indicates the different deviations that can be determined in one or a few similar measurement processes, which are the deviations that appear from:

– Measured position in the horizontal plane;

– Verticality;

– Flatness.

The maximum number of points sufficient to measure for each unit area to determine flatness is described in Figure 38 of TCVN 9262-1:2012.

The various diagrams in this Clause 5 will describe the position and number of measuring points to separately determine the different types of deviations.

5.1.1. Deviation from the structural grid lines

Figure 25 describes how to determine the position of key points and guide columns in the structural grid.

Figure 25 – Position of key points and guide columns in the structural grid

5.1.2. Deviation from secondary lines parallel to the building

The number of measuring points depends on the dimensions of the parts of the building to be measured.

For tall wall-shaped components in general, measurements will be taken at the corner points. For prefabricated or cast-in-situ assembled wall components, additional measurements are required, in both vertical and horizontal directions (for example for elevators) every 3 m (or less).

Figure 26 describes the measuring points to determine the positional deviation from the secondary lines and the vertical planes through these lines.

Columns are always checked in two perpendicular directions.

Figure 26 – Determining the deviation from secondary lines parallel to the building

5.1.3. Deviation from secondary lines perpendicular to the building.

The measuring points as in 5.1.2 can be used to determine this type of deviation. Figure 27 describes the position of measuring points to determine the positional deviation of component edges.

Figure 27 – Position of measuring points to determine the positional deviation of component edges

5.2. Height deviation

The deviation in position in the vertical and horizontal planes or the height of ceilings and floors is determined at the measuring points described in Figure 28.

The overall height or flatness of floors and ceilings is measured according to a horizontal grid determined at distances from 0.5 m to 3.0 m. This distance is selected according to the size and function of the surface to be measured.

Figure 28 describes the position of measuring points at the intersections of grid lines.

Beams are measured for height at at least 3 points as described in Figure 29 (at the top or bottom).

Figure 28 – Position of measuring points at the intersections of grid lines

Figure 29 – Measuring points when measuring beam height

5.3. Verticality

5.3.1. Verticality of multi-story building walls and columns

For walls of multi-story buildings, at least one verticality measurement must be carried out per floor. Figure 30 describes the selected measuring points on each floor having the same horizontal position.

When checking the verticality of columns in multi-story buildings, the points placed at positions 1 and 2 are best (along the centerline of the column) (See Figure 31). If not possible, the measuring points should be placed along the edge of the column at points 3 and 4. The verticality of the column is checked in two perpendicular directions.

Figure 30 – Measuring points on floors with the same horizontal position

Figure 31 – Measuring points for verticality of columns in multi-story buildings

5.3.2. Verticality of tall walls and columns.

The number of measuring points depends on the size of the wall surface to be measured. These types of wall components will be measured at points near the corners (See Figure 32), prefabricated assembled walls should be measured at one point every 3 m.

Figure 32 describes the features to be measured to determine the vertical position deviation. Columns are checked in two perpendicular directions.

Figure 32 – Measuring points for verticality of tall walls and columns

5.4. Eccentricity

Eccentricity is determined at the measuring points described in Figure 33.

In this case,

Where:

T – thickness of the component;

x₁ and x₂ – distances from the vertical line of the horizontal plane to the component;

E – eccentricity.

Figure 33 – Measuring points for determining eccentricity

5.5. Relative position to other components (openings and spaces)

This section provides some examples where accuracy in position and dimensions of components and parts of the construction in relation to other parts is necessary.

Figure 34 – Measuring door and window openings

5.5.1. Window openings and other openings

The dimensions of windows or bounded openings are measured as described in Figure 34. For openings larger than 3 m, additional features must be measured for each additional meter of the opening.

5.5.2. Spaces

Figure 35 describes the features used to measure the length and width of a space. If H or L is greater than 6 m, additional measuring points must be taken, preferably one measuring point every 3 m in the extended direction.

The distance between columns or between columns and wall surfaces is determined by the measuring points described in Figure 36.

Figure 35 – Measuring points for length and width of a space

Figure 36 – Measuring points for determining the distance between columns or between columns and wall surfaces

If the distance is wider than 6 m, additional measurements must be taken in the extended direction, preferably with one additional measuring point every 3 m.

Figure 37 describes the measuring points to determine the height of a space. If L or W is greater than 6 m, additional measurements are required in the extended direction, if possible with one additional measuring point every 3 m.

Figure 37 – Measuring points for determining the height of a space

The above principles are applied when measuring the distance between floor and beam on the underside of the arch, for example 100 mm from each axis and at midspan.

The measuring points to determine the distance between floor and beam are described in Figure 38.

Figure 38 – Measuring points for determining the distance between floor and beam

5.6. Flatness, straightness, design curvature

5.6.1. Floors and ceilings, overall flatness

The measuring points necessary to determine deviations in the overall flatness of floors and ceilings are described in Figure 28.

5.6.2. Floors, local flatness

Figure 39 describes how to determine local flatness. For each surface, one or more measurements are carried out. Each measurement should only be measured within a length not exceeding 2 m. The positions of the measurements are chosen randomly, but it is better to try to choose known locations.

Each measurement consists of 5 measuring points evenly spaced along the length.

Figure 39 – Measuring points for determining the local flatness of floors

5.6.3. Walls, overall flatness

On each vertical face of the wall there will be many measurements depending on the size of the wall, however there should be at least 9 measuring points.

Figure 40 describes the overall flatness of the wall measured according to a defined rectangular coordinate grid with distances from 0.5 m to 3.0 m. This distance depends on the size as well as the function of the surface to be measured.

The perimeter of this grid should be around 100 mm from the edge of the surface.

This procedure can also be used when it is necessary to simultaneously determine different deviations such as position (see 5.1) or verticality (see 5.3).

Figure 40 – Measuring points for determining the overall flatness of walls

5.6.4. Walls, local flatness

The measuring points necessary to determine deviations in the local flatness of wall surfaces can be selected according to the example described in Figure 23.

5.6.5. Calculated curvature

See 4.3

5.7. Other significant deviations

5.7.1. Length of bearing (supporting surface)

When measuring the length of the bearing, select the measuring points as described in Figure 41. It should be noted that the measuring points on each floor component must be marked before assembly at a constant distance C from the edge of the floor component. The distance M from the measuring point on the floor component to the surface of the supporting component is measured after assembly, the bearing length is B = C – M.

Figure 41 – Measuring points for determining the length of the bearing

Measurements are taken from both ends of the component. When the width W of the floor component is less than 1.2 m, only the midpoint needs to be measured, but if W is in the range of 1.2 m to 3 m, it must be measured as described in Figure 41. Components with width W greater than 3 m must be measured additionally in the middle.

5.7.2. Joint width

The width of connecting joints is measured at the points described in Figure 42.

For vertical or horizontal joints that are too long, the distance between measuring points can be chosen from 1.2 m to 3 m.

5.7.3. Step at joint

The step at the joint is measured at point M (See Figure 43), according to the distance from this point to the plane of the adjacent connecting component.

Figure 42 – Measuring points for determining joint width

Figure 43 – Measuring point for step at joint

[1] TCVN to be issued