The BIM Matrix (part 2)

In the previous example, I have shown how to get the quantities for concrete, not including labor or other cost associated with the quantities.

In the pre-design stage, it is important to estimate all the "unknowns" or "unknown variables" as close as possible, therefore the IPD process is very useful. The MacLeamy Curve shows how IPD could potentially help your project finish on time and on budget.

These unknown variables can be calculated simply by using previously bid jobs, and substituting those variables into today's conditions. But the more unknown variables exist, the more equations are required to solve the problem. Here is a simple problem with 3 unknown factors (X, Y, Z), where any of these variables can be any real number, and 3 equations required to solve the problem.

$X + $Y = $Z

$X + $Y = $Z

$X + $Y = $Z

Very simple, three unknowns, three equations.

Well, as shown in part 1, knowing some properties or information about the equation, such as cost of materials (X variable) can help us estimate the other two variables (Y and Z) and narrow down the cost. This example can be used as:

1. equation 1 is simply the cost of material + labor = estimated cost ( labor used from source A)
2. equation 2 is the cost of material + labor = estimated cost (labor rates from source B)
3. equation 3 is the cost of material + labor = estimated cost (labor rates from source C)

As the project keeps growing through other design phases, these unknown factors will keep growing and growing, going from three unknown factors with three equations, to 20 unknown factors, therefore requiring 20 equations. Estimating all unknown factors can be challenging, but can be manageable using the matrix. Below is an example of the cost factor matrix (i.e. for concrete) and all the properties to the material "concrete" can be adjusted or accounted for using the simple matrix. Properties can be added or deleted for different type of material, therefore increasing or decreasing the number of unknown factors.