Which estimating method is NOT recommended for lump sum contracts?

The square footage method is not recommended for lump sum contracts because it often lacks the precision required for accurately estimating costs in such contracts. Lump sum contracts involve a fixed total price for the project, and using a method that estimates based solely on square footage can overlook crucial details about the complexity and specific requirements of the project. These might include variations in material costs, labor intensity, site conditions, and other factors that can significantly impact the final price.

On the other hand, cost-plus estimating, while more flexible and suited for contracts that allow for adjustments based on actual costs, provides a clear breakdown of expenses and ensures that all costs are accounted for. The unit price method can also be useful in determining costs based on specific measurable items, which is beneficial in more detailed and itemized contracts. Historical data methods leverage past project information to make informed estimates, which can also be effective for lump sum contracts, assuming the past projects are comparable to the current one.

Thus, the square footage method, by potentially oversimplifying the complexity and nuances of the project, does not provide the reliability needed for lump sum contracts where precise pricing is critical.