Construction Drawing and Blueprint Reading
Domain 6 tests Construction Drawing and Blueprint Reading: identifying views, reading scales and symbols, and extracting dimensions without scaling off a distorted print.
The drawing set
- Plan - horizontal cut about 1.2 m above floor, showing walls, openings, fixtures and room names.
- Elevation - outside face showing heights, levels, windows, chhajja and parapet.
- Section - vertical cut showing foundation, plinth, DPC, lintel, slab thickness and floor levels.
- Site plan - building position in the plot with boundaries and north arrow.
Conventions
- Scales: 1:100 for plans, 1:50 for details, 1:1000 for site plans. 1:100 means 1 mm on paper equals 100 mm on the ground.
- Levels are written as RL in metres, for example +0.450 for plinth and −0.600 for the foundation bottom.
- Line types: continuous thick for cut walls, thin for dimensions, dashed for hidden work, chain-dotted for centre lines.
- Written dimensions govern; never scale a photocopy.
Worked example
On a 1:100 plan a wall measures 45 mm on paper. Reasoning: 45 × 100 = 4500 mm = 4.50 m. A 230 mm wall should appear as 2.3 mm. If the printed wall measures 5 mm, the sheet has been enlarged or reduced, so use the written dimension 230 mm, not the scaled value.
Traps
- Confusing plan with elevation, or section with elevation.
- Ignoring the stated scale and using a ruler on a reduced print.
- Missing abbreviations: GL (ground level), FL (floor level), CL (centre line), SSL (structural slab level), DPC.