Construction Practices, Estimating, and Project Management
Estimate the work, then manage the promise
Estimating converts drawings into quantities, quantities into hours, and hours into dollars. Begin with a quantity takeoff organized by division, then apply unit costs for material and productivity rates for labor. Labor is where estimates fail: a rate of "200 square feet per worker-hour" means nothing until you attach crew size, shift length, weather days, and site conditions.
Build the estimate from direct material, direct labor (hours × fully burdened rate including payroll taxes, insurance, and benefits), equipment, subcontracts, general conditions (supervision, temporary facilities, permits, cleanup), overhead, contingency, and profit. Contingency is priced risk for defined unknowns, not a slush fund, and it should shrink as the project progresses.
Scheduling. In a critical path method (CPM) network, the critical path is the longest duration path; its activities have zero total float, so any delay there delays completion. Float belongs to the project - spending float on one activity removes buffer for everyone.
Managing. Control the job with submittals, RFIs, daily logs, a written change-order process (no verbal extras), and progress billing tied to measured quantities. Track cost-to-complete, not just percent of budget spent.
Worked example: a four-worker crew places 200 sq ft of formwork per worker-hour. Daily output = 4 × 200 × 8 = 6,400 sq ft. A 20,000 sq ft area needs 20,000 ÷ 6,400 ≈ 3.1 days - round up to 4 with a realistic allowance for layout and cleanup.
Traps: confusing markup with margin; omitting general conditions and labor burden; treating total float as free float; performing a change on a verbal okay; billing 90% when the installed work is 60% complete.