Code of practice for setting out of buildings
1984 Edition

Scope (Clauses 2.0 & 6.1)

• Establishes accuracy criteria for primary reference points crucial in building layout.
• Applicable to construction projects where these points guide structural positioning.

Allowable Deviations (Clauses 2.12 & 11.3)

• Deviations are symmetrical, applicable in both directions.
• Accuracy of primary benchmarks is maintained regardless of errors in national systems.

Accuracy Concepts (Clauses 6.1 & Fig. 2)

• Expressed in terms of angular, linear, and vertical accuracy.
• Utilizes a free network linking primary points with official coordinate systems via a reference point and direction.
• Ensures controlled deviations in building point layout.

Diagram: Free Net Reference System

graph LR
  A[Official Coordinate System] --> B[Reference Point]
  B --> C[Primary Reference Point]
  C --> D[Secondary Baselines]
  D --> E[Building Key Points]
  E --> F[Position Points (e.g., column center lines)]

This standard guarantees precise building layout by systematically managing permissible tolerances and referencing frameworks.

Definitions (Clauses 2.0, 2.12)

• Primary Points: Fundamental reference markers forming the base for building layout.
• Secondary Points: Points derived from primary points, such as baselines.
• Position Points: Specific points like column centerlines.
• Permissible Deviation (E): Maximum allowable symmetric variation, positive or negative.

Permissible Deviations (Clause 8.2)

Formulas for Permissible Deviations

• Distance between points:

[ E = \pm K \sqrt{L} \quad \text{(mm)}, \quad L \geq 5,m ]

[ E = \pm 2K \quad \text{(mm)}, \quad L < 5,m ]

• Angular deviation between two lines:

[ E_{\theta} = \pm 0.067 K \sqrt{L} \quad \text{(degrees)} ]

or in gons:

[ E_{\theta} = \pm 0.075 \frac{K}{\sqrt{L}} \quad \text{(gons)} ]

Notes:

• (L) is the length in meters of the shorter side relevant to the angle or distance.
• (K) is an accuracy constant determined by project requirements.
• These tolerances maintain layout precision aligned with construction needs.

Diagram: Reference Flow

flowchart LR
    A[National Coordinate System] --> B[Primary Points]
    B --> C[Secondary Points (Baselines)]
    C --> D[Position Points (Center Lines)]
    D --> E[Structural Elements]

This illustrates the hierarchy from national references to building components.

Permissible Deviations (Clauses 11.3, Table 11.2)

Setting Out and Levelling (Clause 11.3)

• Instruments must be verified for precision and stability before use.
• Regular recalibration and checks during operations are mandatory.

Permissible Deviation Concept (Clause 2.12)

• Deviations (E) are symmetrical, represented as ±E.
• Applies to linear, angular, and vertical measurements.
• Visualized as tolerance bands around true values (see Fig. 2 of the standard).

Setting Out Principles (Clause 6.1)

• Primary points create the foundational reference system.
• Accuracy depends on relative positioning within the network.
• Coordinates are established from traverse networks linked to official systems.

Diagram: Setting Out Network

graph LR
A[Official Reference Point] --> B[Primary Reference Point]
B --> C[Secondary Baselines]
C --> D[Building Key Points]
D --> E[Position Points (e.g., column centers)]

Additional Notes

• Use metric, metallic woven, or glass fibre tapes as per specification.
• Errors in national coordinate systems do not affect building point accuracy due to referencing methods.

This summary aligns with IS 11134's guidelines on accuracy, tolerances, and layout methodology.

Accuracy Criteria (Clause 11.2.1)

Note: Project specifications may mandate stricter limits.

Reference Systems (Clauses 6.1 & 6.2)

• Primary System: Network of primary points adjusted collectively (least squares).
• Secondary System: Derived from primary points, used for detailed layout.
• Connection to Official System: Preferably via one reference point and direction to minimize cumulative errors.

Methods to Establish Primary Points

• Loop traverses
• Redundant resections
• Intersection methods
• Simultaneous polar method
• Anblock adjustment method (illustrated in Fig. 5)

Diagram: Reference System Hierarchy

graph TD
  A[Official Coordinate System] -->|Reference Point & Direction| B[Primary System]
  B --> C[Secondary System]
  C --> D[Building Main Points]
  D --> E[Position Points (e.g., column centers)]

Additional Information

• Vertical and angular deviations are controlled as per IS 11134.
• Appropriate measurement tools such as metric tapes and glass fibre tapes are specified.
• Primary point accuracy is ensured by adjusting the entire network, not isolated points.

This framework guarantees precise and traceable construction layouts.

Primary Points (Clause 2.1)

• Determined through high-precision measurements.
• Referenced to national or municipal coordinate systems.
• Serve as foundational markers for deriving secondary points.
• Coordinates obtained via traverses or triangulation networks.
• May be locally adjusted while preserving overall network integrity.

Accuracy Specifications (Clause 6.1)

• Primary points must satisfy stringent relative positional accuracy.
• Expressed as permissible angular and linear deviations.
• Errors here influence secondary points and overall building layout.

Permissible Deviations (Clause 7.3)

• Secondary points have defined tolerance limits relative to primary points.
• Deviations vary based on project scale and accuracy needs.

Secondary System (Clause 7.2)

• Comprises grids or baselines derived from primary points.
• Used for detailed layout tasks like locating column centerlines.

Typical Accuracy Parameters

Diagram: Reference Point Systems

graph TD
  A[National/Municipal System]
  B[Primary Points]
  C[Secondary Points (Grid/Baselines)]
  D[Building Main Points]
  A --> B
  B --> C
  C --> D

Summary

• Primary points are high-precision references tied to official coordinates.
• Secondary points, derived from primary, facilitate detailed layout.
• Permissible deviations ensure construction accuracy.
• Use traverses and triangulation for establishing primary points.
• Control angular and linear errors as per IS 11134.

Overview (Clauses 6.1 & 7.1)

• Accuracy defined for relative positions within and between secondary systems and between primary and secondary points.
• Primary points act as key reference markers for building layout.

Permissible Angular Deviations (Fig. 2)

• Depend on network order.
• Typical formula:

[ \Delta \theta = \frac{30''}{\sqrt{L}} ]

Where (L) is traverse length in kilometers.

Accuracy Limits

Network Configuration

• Primary system connects to official coordinates via one reference point and direction.
• Secondary baselines extend from primary system.
• Position points (e.g., columns) set relative to secondary baselines.

Vertical Accuracy (Clause 11.1)

• Benchmarks must maintain ±5 mm relative vertical accuracy.

Diagram

graph TD
  A[Official Coordinate System]
  B[Primary Network]
  C[Secondary Network]
  D[Position Points]

  A -->|Reference Point & Direction| B
  B -->|Baselines| C
  C -->|Layout| D

Summary

Strict adherence to angular and linear tolerances in primary points is essential to ensure accurate building layouts as mandated by IS 11134.

Secondary System (Clause 7.2)

• Secondary points provide references for detailed building layout.
• Often paired to form baselines.
• Together with main points, they compose the secondary layout system.
• Derived from primary points using methods such as intersection, resection, and polar coordinates.
• Accuracy depends on the integrity of the primary system.

Permissible Deviations (Clause 7.3.3)

• For points in different secondary systems:

[ \text{Allowed deviation} = K \times L \quad \text{(mm)} ]

Where (L) is distance in meters and (K) is an accuracy constant.

Personnel Responsibilities

• Primary system: qualified surveyors or engineers.
• Secondary system: engineers or surveyors familiar with construction surveys.
• Position points: typically set out by site supervisors.

Permissible Deviation Table

Diagram

flowchart TD
    A[Primary Points] --> B[Secondary Points]
    B --> C[Baselines (Secondary System)]
    C --> D[Position Points (Columns, Walls)]

Note: Coordinate with local survey authorities to ensure alignment with official coordinate systems.

Key Insights (Clauses 5, 6, 7, 8)

• Accuracy reduces with the number of measurement steps due to cumulative errors; minimizing operations is essential.
• Primary points are critical references for building layout.
• Accuracy is specified for points within the same secondary system, between secondary systems, and between primary and secondary points.
• Defines accuracy thresholds for relative positioning of position points.

Accuracy Limits

Note: Variations depend on project precision and measurement techniques.

Error Propagation Formula

[ \sigma_{total} = \sqrt{\sum_{i=1}^n \sigma_i^2} ]

Where (\sigma_i) is the standard error of each measurement step, and (n) is the number of steps.

Setting Out Guidelines

• Employ a free network connected to official coordinates via a single reference point and direction.
• Limit inaccuracies by reducing the number of polygons and measurement sequences.
• Control layout of corner and baseline points to prevent misalignment.

Diagram: Free Net Connection

graph LR
  A[Official Coordinate System]
  B[Primary Reference Point]
  C[Primary Reference Direction]
  D[Secondary Baselines]
  E[Main Building Points]
  F[Position Points]

  A --> B
  B --> C
  C --> D
  D --> E
  E --> F

Summary

IS 11134 promotes minimizing measurement steps and maintaining rigorous accuracy controls for primary and secondary points to achieve precise building layouts and prevent construction discrepancies.

Marking Primary Points (Clauses 6.5, 10.4)

• Primary points must be marked with precision, for example using punch marks.
• Locate primary points outside active work areas to avoid accidental displacement.
• Points transferred during layout should be immediately marked to secure their positions.

Accuracy and Permissible Deviations (Clause 8.2)

• Permissible distance deviation for length (L) (meters):

[ \pm K \sqrt{L} \text{ mm} ]

• For (L < 5, m):

[ \pm 2K \text{ mm} ]

• Angular deviation for two lines:

[ \pm 0.067 K \sqrt{L} \text{ radians} \quad \text{or} \quad \pm 0.075 K \sqrt{L} \text{ gons} ]

Reference System and Network

• Primary points form a free network connected to official coordinate systems.
• Accuracy of building points is independent of errors in national or municipal coordinate systems.

Diagram

graph LR
A[National Reference] --> B[Primary Reference Point]
B --> C[Secondary Baselines]
C --> D[Main Building Points]
D --> E[Position Points]

Summary

Mark primary points accurately and protect them from movement. Use the constant (K) and distance (L) to calculate permissible deviations, ensuring construction accuracy.

Marking Procedure (Clause 10.4)

• Immediately mark points after transfer to prevent displacement.

Verification Checks (Clauses 2.8, 10.5)

• Check measurements must be independent, employing instruments of equal or superior accuracy.
• Optical plumb lines require verification with similarly precise instruments.

Instrument Calibration (Clause 11.3)

• Instruments must be checked prior to initial use and frequently rechecked.
• Adjustments should be made as necessary to maintain precision.

Permissible Deviations in Level Differences (Table 11.2)

Distance Measurement (Clause 4.1)

• Use tapes conforming to IS 1269-1964.
• Corrections for temperature, sag, slope, and tension must be applied.
• Employ tension devices with tapes.
• Use different tapes for check measurements adhering to the same IS.

Correction Formula

[ L_c = L_m + \Delta T + \Delta S + \Delta Sl + \Delta Te ]

Where:

• (L_c): Corrected length
• (L_m): Measured length
• (\Delta T): Temperature correction
• (\Delta S): Sag correction
• (\Delta Sl): Slope correction
• (\Delta Te): Tension correction

Workflow Diagram

flowchart LR
    A[Measurement] --> B[Mark Transferred Point]
    B --> C[Verification Measurement]
    C --> D{Within Accuracy Limits?}
    D -- Yes --> E[Proceed with Data]
    D -- No --> F[Recalibrate Instruments]
    F --> G[Adjust and Repeat]
    G --> C

This process ensures reliability and precision in layout and leveling.

Key Formulas

• Permissible deviation for position point distances:

[ E = \pm K \sqrt{L} \quad \text{(mm)} ]

• For distances less than 5 meters:

[ E = \pm 2K \quad \text{(mm)} ]

• Permissible angular deviation between two lines:

[ E_{\theta} = \pm 0.067 K \sqrt{L} \quad \text{(degrees)} ]

or equivalently:

[ E_{\theta} = \pm 0.075 \frac{K}{\sqrt{L}} \quad \text{(gons)} ]

Where:

• (L) is length in meters (shortest side of angle)
• (K) is a constant from Table 1 based on accuracy class

Table 1: Accuracy Class Constants

Permissible Deviations in Vertical Levels (Clause 11.3)

Notes

• Deviations are symmetric (±).
• Levelling instruments must be regularly checked and adjusted.
• Project-specific tolerances may override these values.

Decision Flow

graph TD
A[Distance L] --> B{Is L < 5 m?}
B -- Yes --> C[Permissible Deviation = ± 2K mm]
B -- No --> D[Permissible Deviation = ± K√L mm]

Instrument Verification (Clause 11.3)

• Instruments must be checked for precision and stability before use.
• Frequent revalidation is required.
• Permissible deviations for level differences are:

Causes of Centering Errors (Clause 6.6)

• Instrument errors including optical plummet inaccuracies.
• Poorly defined or rough reference points.

Permissible Deviations in Layout (Clauses 2.12 & 8.2)

• Position point deviation formula:

[ \pm K \sqrt{L} \quad \text{(mm)} ]

• For (L < 5 m):

[ \pm 2K \quad \text{(mm)} ]

• Angular deviation:

[ \pm 0.067 K \sqrt{L} \quad \text{(radians)} \quad \text{or} \quad \pm 0.075 K \sqrt{L} \text{ (gons)} ]

• Values of (K) based on accuracy needs:

Summary

• Regular instrument and point verification minimizes errors.
• Use specified permissible deviations according to application.
• Apply formulas consistently with constant (K).

Flowchart

flowchart TD
    A[Start Layout] --> B[Verify Instrument Accuracy]
    B --> C{Is Instrument Accurate?}
    C -- No --> D[Adjust and Reverify]
    C -- Yes --> E[Define and Mark Points Clearly]

Grid Concepts (Clause 2.4)

• Grid Definition: Two orthogonal sets of horizontal lines forming a coordinate system.
• Grid Types:
  • Site Grid: Used for large sites with multiple parallel building lines, simplifying layout.
  • Structural Grid: Relates to center lines of structural elements, referenced to base lines.
  • Location Grid: Utilized by planning authorities for defining legal boundaries and streets with high precision.

Specifications and Methods

• Primary System:

  • Network of primary points adjusted simultaneously via least squares.
  • Methods include loop traverses, redundant resections, intersections, simultaneous polar, and anblock adjustments (see Fig. 5).
  • Prefer avoiding connecting site systems to official systems by a single reference point.

• Secondary System:

  • Reference points and directions chosen for internal precision.
  • Coordination with authorities is essential before layout.

• Accuracy:

  • Location grids are considered free of error per legal standards.
  • Internal building accuracy ensured by referencing one point and one direction per grid square.

Additional Considerations

• Vertical transfers and plumb line deviations must be controlled (Clause 2.4:10).
• Primary system adjustments must be executed as a whole.
• Specialized precision tasks may require tailored approaches.

Example: Anblock Method

graph LR
A[Instrument Station 1] --> B[Free Net Point 1]
A --> C[Free Net Point 2]
D[Instrument Station 2] --> B
D --> C
E[Instrument Station 3] --> B
E --> C

Grid Type Summary

Always consult relevant authorities and employ least squares adjustments for primary points.

Setting Out (Clause 8.3)

• For accuracy constants (K \leq 5), follow Clauses 4.1 and 4.2 for setting out.
• Typical building construction applies, but precision machinery setting requires specialized handling.

Accuracy Requirements (Clauses 6.1 & 7.3)

• Primary points establish the reference framework.
• Permissible deviations for secondary points and angular measurements are specified.
• Limits vary according to project scale and precision demands.

Angular Permissible Deviations (Fig. 2)

• Define allowable angular errors during layout to ensure structural alignment.

Network and Reference Systems

• Utilize a free network derived from traverses.
• Connect to official coordinate systems via a single reference point and direction.
• Building point accuracy remains independent of national system inaccuracies.

Example Permissible Deviations

Diagram: Free Net Layout Concept

graph LR
  A[Official Reference Point] --> B[Primary Reference Point]
  B --> C[Secondary Baseline]
  C --> D[Building Main Points]
  D --> E[Position Points (e.g., column centers)]
  A --> F[Reference Direction]

Note

Always consult IS 11134 Clauses 4.1, 4.2, 6.1, 7.3, and 8.3 for detailed tolerances and formulas.

Accuracy Specifications (Clause 6.1)

• Defines permissible deviations for positioning primary points used as building references.
• Uses a free network connected to official systems by one reference point and direction.
• Internal accuracy is maintained independently of national system errors.

Angular Deviations

• Refer to Fig. 2 (not included here) for angular accuracy representation.
• Expressed as allowable angular deviations during layout.

Grid Systems (Clause 2.4)

• Site Grid: For multiple parallel building lines to simplify layout.
• Structural Grid: Center lines for structural elements referenced to baselines.
• Location Grid: Legal boundaries and axes, with accuracy as per local regulations.
• Layout is performed using one reference point and direction per grid cell.

Vertical Transfer Accuracy (Clause 11.2.1)

Additional Notes

• Consult local authorities regarding reference points and accuracy requirements.
• Project documents might impose stricter tolerances.

Diagram

flowchart LR
    A[Official Coordinate System]
    B[Primary Reference Point]
    C[Primary Reference Direction]
    D[Secondary Baselines]
    E[Structural Grid Center Lines]
    F[Building Components]

    A --> B
    B --> C
    C --> D
    D --> E
    E --> F

Summary

IS 11134 stresses precision in layout through primary and secondary reference systems, permissible angular and vertical deviations, and structured grid frameworks for exact building positioning.