How to Check Dimensions on Drawings vs Site? | Q & A

Checking dimensions is about accuracy, verification, and control. A site engineer must never rely only on tape measurement—the process is systematic.

1. Check Drawing Dimensions First (Before Going to Site)

• Use dimensions written on drawings, not scaled values

• Confirm latest revision

• Cross-check with:

  • Architectural drawings

  • Structural drawings

• Note grid-to-grid dimensions and overall dimensions

Rule: “Do not scale—only read dimensions.”

2. Establish Reference Points on Site

• Identify permanent reference benchmarks (BM)

• Fix grid lines using:

  • Total station / theodolite

  • Tape (for small works)

• Mark center lines of columns and walls

3. Setting Out on Site

• Transfer drawing dimensions to site using:

  • Grid intersections

  • Center-line method

• Mark:

  • Column centers

  • Beam center lines

  • Wall lines

Tools used:

• Total station

• Measuring tape

• Chalk line

• Plumb bob / laser level

4. Cross-Check Methods (Very Important) a) Grid-to-Grid Check

• Measure distance between grids on site

• Compare with drawing dimensions

b) Overall vs Individual Dimensions

• Sum of individual dimensions = overall dimension

• If mismatch → error in marking

c) Diagonal Check (Squareness)

• Measure diagonals of a rectangular layout

• Diagonals must be equal

5. Vertical Dimension Checks (Levels)

• Use auto level / dumpy level / laser level

• Check:

  • Plinth level

  • Beam bottom level

  • Slab top level

• Compare RL values with drawings

6. Tolerance Awareness

Typical construction tolerances:

• Column position: ±10 mm

• Slab thickness: ±5 mm

• Beam width: ±5–10 mm

Minor deviation may be acceptable; major deviation is not.

7. During Execution Checks

• Recheck after:

  • Excavation

  • PCC

  • Shuttering fixing

  • Reinforcement fixing

• Do not wait until concreting day

8. What If Dimensions Don’t Match?

• Stop work immediately

• Recheck drawing revision

• Verify architectural vs structural drawing

• Inform senior engineer / consultant

• Never adjust dimensions without approval

One-Line Interview Answer (Perfect)

I check drawing dimensions using written values, set out grids on site with reference benchmarks, cross-check using diagonals and overall dimensions, verify levels with leveling instruments, and immediately report any mismatch.

Common Interview Follow-Up

Q: Why shouldn’t we scale drawings?
A: Scaling is inaccurate due to printing and distortion—only written dimensions are reliable.