It is during takeoff that the full benefit of using models becomes evident. Models allow you to eliminate much of the input required for ordinary item or assembly takeoff. Based on the setup, the fields in a model could be partly or entirely prefilled for model takeoff. Essentially, all values needed to calculate quantities for your estimate come from variables and questions. Consider the following ways a model can obtain input:
- From variables – A model can obtain the values it needs entirely from the variables that are part of each item and assembly. In effect, this is a simple batch method of takeoff that works like item and assembly takeoff. Without defaults or questions, you need to enter the variables, location, WBS values, and productivity adjustment for each item separately.
- From variables with defaults – If instead, the model includes defaults (assumptions) in the variables, you will not have to enter those values during model takeoff. For example, you could set up a default slab depth of 6" in the Slabs on Grade assembly to prefill that field so it will not need input. And if you hide variables with defaults, you won’t even see them during takeoff.
- Similarly, you can set up defaults for the fields common to every item and assembly, such as the location, WBS values, and productivity adjustment.
- From variables and questions – A model can also use questions to request values, which it then feeds to associated fields in every item and assembly in the model. A single question can be used to provide the input for many variables. For example, your reply to 'What is the garage length in feet?' could be used to prefill all Length' variables in the model. The same reply could be used to calculate the Wall Length' variable. With both variables and questions, you can reduce the amount of input even further.
- From variables and questions with defaults – Most powerful of all is a model that includes defaults for both variables and questions. Such a model could prefill the majority of the fields so that very little input will be required at takeoff.