Construction Drawing
This domain tests whether you can read a drawing as a builder does: choose the right scale, identify line types, dimension correctly, and translate a scaled plan into real dimensions on site.
Rules of the drawing sheet
- Scales: site plan 1:500 or 1:1000; floor plan 1:100; construction details 1:20 or 1:10.
- Line types: continuous thick for visible outlines, continuous thin for dimension and hatching lines, dashed for hidden work, chain thin for centre lines.
- Dimensions are written in millimetres with no unit symbol after each figure; a general note states all dimensions in mm. Dimension lines carry 45° oblique strokes or arrowheads, and the smallest dimensions sit nearest the object.
- A plan is a horizontal cut taken about 1.2 m above floor level; a section shows cut surfaces hatched; an elevation shows the external face only.
- Symbols: a door is a quarter-circle swing, a window is thin lines within the wall thickness, a level is an inverted triangle with its reduced level.
- Every sheet carries a title block, drawing number, revision, scale and north arrow.
Worked example
A room measures 4.2 m × 3.6 m internally with 230 mm walls, drawn at 1:100. On paper the room is 42 mm × 36 mm. Overall size = (4200 + 460) × (3600 + 460) = 4660 × 4060 mm, that is 46.6 mm × 40.6 mm on the sheet. Floor area is 4.2 × 3.6 = 15.12 m²; the paper area of 42 × 36 mm is a drawing area, not a scaled area to convert by 100.
Traps that cost marks
Writing mm on every dimension; scaling an area by the scale factor instead of its square; reading an elevation as a plan; omitting the north arrow; forgetting that a section reveal on plan is drawn hatched only where it is cut.