Scope, Schedule, and Cost

$/square foot Estimation:

This method relies on historical cost data. It is reasonably reliable in general, however should be considered the least reliable method of the three discussed. See below for an example.

Bottom-up Estimation:

This method is based on historical cost data, current cost data, or a combination. It is reasonably reliable overall but requires accurate quantity takeoffs. See below for an example.

Trade Quotes:

This method is the most reliable as the the cost data will be provided by the trade that will be performing the work. See below for an example.