the criteria for choosing type of estimate in any building construction are given below.
1.What phase is the project in?
Perhaps the most important, or at least first, determining factor for selecting the estimating method, or approach, is the project phase. Where is the project in it’s life-cycle? If it is in the conceptual design phase you might consider using the Universal Factors method. This method, in it’s simplest form, works as a type of “analogy” estimating approach. If you have similar past projects in your “bottom right-hand drawer” then you may be set. Otherwise, you may need to use a Universal Factors model.
2.What project data is available?
As they say “data is king”. That statement certainly holds true for estimating. Not only the volume, but the type of data available to you, can make all the difference in the method and accuracy of your estimate. Review the data available to you (technical or unit cost). The amount of data on hand can help you decide which method you will use, the cost drivers, and many more aspects of your estimate.
3.What is the purpose of the estimate?
You should always keep in mind the purpose of the estimate you are developing. Is your estimate attached to a detailed bid or proposal for a potential client or is it going to be used to “cost out” one of multiple approaches to a solution for management review? If the latter, perhaps all you need is a Rough Order of Magnitude (ROM) estimate? The estimates purpose (read: audience) determines the approach you take and what attributes of your estimate you include or highlight.
4.What is your time-frame?
When you have the time (and data points), it is often best practice to develop as detailed an estimate as possible. This is especially true when estimating construction or preparing a T&M bid or proposal.
5.What estimating tools are available?
After all is said and done, it may come down to the tools you have in your toolbox. Most estimators, and I know I am in this category, are Excel aficionados. You can often find me buried in a spreadsheet somewhere. If I am pulling together a “back-of-the-envelope” estimate I will often use Excel. However, Excel has it’s limits. There are multiple tools on the market for QTO estimating that provide management capabilities over and above what Excel can offer.