Basic Numeracy and Measurement
What this domain covers
Numeracy and measurement questions check that you can take off quantities from a drawing, count materials correctly, check loads against the duty class, and measure plumb, level and square with real instruments.
Core rules
- Work in consistent units: 1 m = 1,000 mm; 1 kN ≈ 102 kg, so 1 t ≈ 9.8 kN. Area in m², volume in m³, duty in kN/m².
- Scale: at 1:100, 1 mm on paper = 100 mm real, so 20 mm scaled = 2.0 m.
- Counts: bays = length ÷ bay spacing (round up, then recompute the actual spacing); standards per face = bays + 1; lifts = height ÷ lift height; transoms = standard positions × lifts.
- Bracing: a 45° brace across a square bay equals span × 1.414 (Pythagoras).
- Load check: platform area × duty = total load; compare with the design and post the class.
- Instruments: tape pulled taut and horizontal, spirit level checked in both directions, plumb bob on a still day, laser level for long runs - read the bubble, not the frame.
Worked example
A 12 m long, 6 m high independent scaffold: bays 2.0 m, lifts 2.0 m, platform 0.6 m wide, duty 2.0 kN/m². Bays = 12 ÷ 2.0 = 6, so 7 standards per face and 14 standards in all. Lifts = 6 ÷ 2.0 = 3. Transoms = 7 positions × 3 lifts = 21, each about 1.2 m + 2 × 100 mm overhang ≈ 1.4 m. Platform area per lift = 12 × 0.6 = 7.2 m², so load = 7.2 × 2.0 = 14.4 kN ≈ 1,470 kg uniformly distributed over that lift. Boards per lift: 12 ÷ 3.0 = 4 per row, and 3 rows of 225 mm boards cover 0.675 m, satisfying the 0.6 m width.
Traps
Mixing kN with kg, forgetting coupler and overhang allowances, measuring with a slack tape, and reading the duty as a per-plank figure.