LECTURE NO.6: Building Construction Estimates for Construction Management Tools

Construction estimating

— determines the quantities and resources associated with construction work.

Construction Quantity

— is the measurable amount of work associated with an activity.

Quantity

— is the starting point for determining resource requirements and duration.

Productivity

— measures the relationship between output and resource input.

Productivity = Output ÷ Input

The basic relationship of productvity is:

Labor input:

4 workers x 1 day

= 4 person-days

Therefore:

Productivity = 80 m² ÷ 4 person-days

= 20 m²/person-day

Example

A four-person crew installs 80 m² of masonry in one day.

Labor Productivity = Quantity of Work ÷ Labor Input

For labor productivity:

Accomplishment per Person per Day

— expresses how much work one worker can accomplish in one working day.

APD = Total Accomplishment ÷ (Number of Persons × Number of Days)

Accomplishment per Person per Day formula

Labor input:

5 workers × 5 days = 25 person-days

Therefore:

APD = 250 m² ÷ 25 person-days

APD = 10 m²/person/day

Example:

A crew of 5 workers completes 250 m² of plastering in 5 days.

Find APD

Unit Duration

— refers to the time required to accomplish a unit of work under specified resource and productivity conditions.

Duration = Quantity ÷ Production Rate

Unit Duration formula

Therefore:

Duration = 600÷60

Duration = 10 days

Example:

Required masonry:

600 m²

Crew production:

60 m²/day

Find Duration

Manpower Planning

Determine how many workers are required.

Duration Planning

Determine expected activity duration.

Material Procurement

Determine when materials must be available.

Equipment Planning

Determine equipment requirements.

Scheduling

Assign activities and durations to the construction schedule.

Progress Monitoring

Compare planned quantities with actual quantities.