Cost Indices and Parametric Estimating - Examples & Applications

Parametric Estimating Applications

Examples of calculating conceptual budgets using indices and capacity factors.

Example 1: Using a Cost Index for Time Adjustment

Adjusting for time and inflation using index ratios.

10,000 \text{ m}^2

warehouse was constructed in 2010 for a total cost of

\

1,500,000

. The Engineering News-Record (ENR) Building Cost Index at the time of construction in 2010 was

4500

. The current ENR index for the year 2024 is

8100$.

Estimate the conceptual budget required to build the identical warehouse today in the same location.

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Example 2: The Capacity Factor Method

Scaling costs non-linearly using historical capacity exponents to account for economies of scale.

An engineering firm designed and built a

50 \text{ MGD}

(Million Gallons per Day) water treatment plant for

\

40,000,000

. They are asked by a different municipality to provide a conceptual estimate for a much larger,

80 \text$ plant of the same technology.

Historical data suggests the capacity scaling exponent (

X

) for this specific type of water treatment plant is

0.70

. Determine the conceptual budget for the new plant.

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Example 3: Adjusting for Both Time and Location

Combining national inflation indices and city cost indices to calculate a final conceptual budget.

A structural steel warehouse was constructed in Chicago, IL in 2018 for a total cost of

\

3,500,000$. An estimator needs to provide a conceptual budget for building the exact same warehouse in Denver, CO in 2024.

Historical Data available:

2018 National Average Index: $100$
2024 National Average Index: $135$
Chicago City Cost Index (CCI): $115$ (relative to a national average of $100$ )
Denver City Cost Index (CCI): $108$ (relative to a national average of $100$ )

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Example 4: Parametric Cost per Parameter (Square Foot)

Using square foot unit costs derived from historical data for a preliminary budget.

A developer wants to build a new

45,000 \text{ sq ft}

medical office building. They do not have architectural drawings yet. The estimating firm looks at their database of the last five medical office buildings they constructed in the same region over the past two years:

Project A: $30,000 \text{ sq ft}$ , $\$ 8,100,000$
Project B: $50,000 \text{ sq ft}$ , $\$ 14,500,000$
Project C: $25,000 \text{ sq ft}$ , $\$ 6,500,000$

Determine the average historical cost per square foot, and use it to estimate the developer's new project.

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Key Takeaways

Index formulas multiply the historical cost by the ratio of the target index over the base index to account for inflation.
When adjusting for both time and location, apply the adjustments sequentially: transform the cost to the new location first using city indices, then account for inflation using national indices.
Using a capacity factor exponent less than $1.0$ mathematically models economies of scale (e.g., doubling the capacity of a plant does not double the cost).
Basic parametric estimating relies on establishing average unit costs per parameter (like square footage) from recent historical data and applying it to the new project's known parameters.

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