Building unit costs from your own completed jobs
A developer asks the owner of a small building company to price six townhouses by Friday. Her last three framing prices came from a price book, adjusted after each lost bid. Yet her company has framed three similar blocks in two years, with every hour coded by activity in payroll.
Take each finished job's final hours and costs by cost code, divide them by the quantity installed, in a unit you can take off the next job's drawings, and record the conditions that explain why jobs differ. Keep labour as hours per unit, to price at today's wages, and dollar costs with their dates, to bring forward to today's prices. A university construction text notes that historical cost data is useful for estimating only if it is collected and organized to fit how it will be used.
From closed jobs to a cost file
- Use final numbers from the closed job's final cost report, after the last invoice and back charge, not the last forecast.
- Clean each code first: take out hours for change orders, standby and damage by others, and note them. Keep your own rework in; the next job will have some too.
- Measure the quantity in your estimating unit from the as-built drawings: square metres of floor, metres of wall, cubic metres of concrete.
- Record the conditions beside the rate: storeys, roof, layout, season, access, crew. They explain the spread and show which past job the next one resembles.
- Keep labour in hours per unit, priced at today's wages. Bring dollar costs forward with current quotes or a published index, such as Statistics Canada's quarterly building construction price indexes.
- Choose from the range, not the best job: start from the most similar jobs, adjust for known differences, and write down why.
- Add every finished job, and compare what you priced with what it took; the post-project review is where the team explains the gap.
Common mistakes
- Dividing a job's total cost by its floor area and using the result for every trade.
- Taking the best job's rate because it wins bids.
- Storing labour in dollars, so a raise looks like a slower crew.
- Leaving change-order and standby hours in the base code.
Action list
Start your cost file
- Pick the three or four biggest labour activities
- Pull final hours and costs from your last three jobs
- Take out changes, standby and damage by others
- Measure quantities in your estimating unit
- Write the conditions beside each rate
- Price hours at today's wages
Check your understanding
Two finished jobs framed at 1.70 and 2.00 hours per m². The new one resembles the first but has a tight lot and a winter start. Which rate do you use?
