How models obtain values
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 must 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.