Detail Estimation Start with WBS Direct Cost Indirect Cost Man (Labor) Machine (Equipment) Material (Material) Management (Overhead) Temporary Transportation Storage Mark-up (VAT, Taxes, Profit, Insurance, etc)
Material Cost Cost = unit Price x Quantity KEYS Fluctuation of unit price Quantity of Material use Combination of materials Example: Activity A Concrete 10m3 = 2,000x100 = 20,000 Steel 1 ton= 1,500x 1= 1,500 Formwork = 1,000 x300=300,000 Material Cost = 321,500 Baht
Labor Cost Cost = Unit price x Duration x Numbers Duration depends on productivity rate Example Activity A 20 Carpenters for 10 Days 300 Baht/man/Day 10 Labors for 10 Days 150 Baht/Man/Day Labor Cost = (20x10x300)+(10x10x150) = 60,000 +15,000 = 75,000 Baht O.T Rate Bonus Rate
Labor Cost Productivity Rate examples 1 labor 3 sq.m. brick wall per day 1 Carpenter 1 footing formwork/day Subcontract Rate examples 300 Baht/1 Door installation 50 Baht/1 meter installation 3 Baht/1 Kg of Steel reinforcement Normally subcontract rate is more expensive.
Equipment Cost O & O Cost O1 - Owning Cost Example You bought A Honda 600,000 Baht and sold it 5 years later at 300,000 Baht You paid 600,000-300,000 = 300,000 for 5 years Approximately; You do pay 300,000/365/5 = 164.38 Baht/Day owning this Honda *** Do not forget interest, taxes, inflation, etc.
Equipment Cost An example You use an excavator for a trench excavation 100m 3 1 round of operation the excavator can take 0.1 m 3 1 round of the operation takes 30 seconds (Load - Turn- Dump-Turnback) 1 Hour productive time = 40 min 1 Hour, the excavator can produce = 80 rounds * 0.1 m3 = 8 m3 To finish the excavation, it takes 100/8 = 12.5 Hours Equipment Cost = 12.5*58.5 (assume) = 731.25 Baht
Common Errors in Cost Estimation Forget items in WBS Poor productivity estimation Some hidden cost and risk Temporary works Wrong unit price, Market condition Wrong quantity estimation, Human error Missing in quality of work Transportation