MEASUREMENT & ESTIMATING

Measurement & Estimating



Measurement & Estimating

Introduction

The heart and core of this paper is to critically analyze the concept of cost and budgeting estimate of construction. This tool is a working example of a parametric cost model. A parametric cost estimating model is made up of one or more algorithms or cost estimating relationships (CERs) that translate technical and/or programmatic data (parameters) about a product or asset into cost results. The algorithms are commonly developed from regression analysis of historical project information; however other analytical methods such as neural networks are sometimes used.

The models are very useful for cost and value evaluations early in the project life cycle when not much is known about the project scope. The models are limited in accuracy and usage due to the many assumptions built into the algorithms. Also, the validity of the model is usually limited to certain ranges of parameter input values. Due to these limitations and constraints, it is incumbent upon the user to thoroughly understand the basis of a parametric model(Appleby, 2006,, 410).

Cost Model

This illustrative cost model is made up of a set of algorithms -- one for each of the "systems" that make up a building and one for the architects fees to design the building.

The building cost accounts shown are the major divisions of the CSI Uniformat which is commonly used for parametric building cost evaluations due to their "systems" orientation.

The model is generally applicable to the typical kinds of buildings found in an industrial or commercial setting in the United States (up to 7 stories, steel or concrete structure). This includes offices, warehouses, industrial buildings, and labs. It does not apply to residential or wood construction. It does not cover buildings over 7 stories or monumental grade buildings with elaborate closures and finishes. It also does not provide for clean room conditions. The estimate does NOT include contingency.

All cost estimates should include a contingency allowance to cover for unidentified but expected cost occurrences within the project scope. Contingency is usually estimated through the application of risk analysis techniques.

Input Parameters

The following is the list of model input elements, their use, and range of values.Case Description

(Optional) labeling of parameter set, especially useful if printing the results for distribution and/or saving the parameters for later use.Floor Area

In square feet - Enter the total usable square feet of the building floor area measured from wall-to-wall including all stairwells, closets, etc. Include all floors in multi-story buildings, except use 1/2 the measured area for basement levels. No default. (The system has a scaling adjustment to account for economies of scale -- 20,000 SF yields no adjustment.)Floor Height

In feet - Enter the average number of feet from the floor surface on one story to the floor surface of the next. For single story buildings use the distance from the floor slab to the eave. For multi-story buildings, divide the total building height from base slab to roof eave by the number of floors.Number of Floors

In whole number - Enter the number of ...