Estimating and Plan Reading
Reading the drawing set
Start with the cover sheet and drawing index, then the general notes, then plans, elevations, sections, and details. Learn to read the title block, north arrow, graphic scale, grid lines, and dimension strings (feet-inches notation). Match symbols to the legend, and cross-check the door, window, finish, and equipment schedules against the plans - schedules govern quantities and specifications for those items.
Quantity takeoff discipline
Take off in a consistent sequence (by CSI division or by assembly) and mark up the drawings as you count so nothing is double-counted. Distinguish net quantities from order quantities: add waste, overlap, and breakage. Know the difference between bank (in-place), loose, and compacted volumes for earthwork - excavated soil swells, and backfill shrinks.
Traps
- Forgetting waste factors or ordering exact net quantities.
- Reading a scale wrong when a drawing is plotted at reduced size - always verify with a known dimension.
- Mixing units: cubic feet for concrete volume but cubic yards for ordering.
- Ignoring specification sections that change material (e.g., a higher-strength mix) from what the plan note shows.
Worked example - concrete slab
Slab 30 ft × 40 ft at 6 in thick. Volume = 30 × 40 × (6 ÷ 12) = 600 ft³. Convert: 600 ÷ 27 = 22.22 yd³. Add 5% waste: 22.22 × 1.05 = 23.3 yd³, so order 24 yd³ (never round down).
Worked example - earthwork
100 yd³ of bank clay with 30% swell becomes 130 yd³ loose for hauling; the same material compacted back may shrink, so order fill by compacted volume, not loose volume.