Final answer:
There are four project delivery methods where the construction cost is determined after the design phase: Cost-Plus Contract, Design and Build, Time and Material Contracts, and Unit Price Contract. These methods necessitate an accurate engineering design process, including prototypes and mathematical models, to predict and later finalize costs.
Step-by-step explanation:
In the realm of engineering and construction, certain project delivery methods determine the construction cost only after the design has been completed. Notably, there are four such methods where costs are finalized post-design:
- Cost-Plus Contract - In this method, the client agrees to pay the actual construction costs plus a fee for the contractor's services, which could be a fixed amount or a percentage of the costs.
- Design and Build - While a single entity is responsible for both design and construction, the cost is often not determined until the design is sufficiently advanced or completed.
- Time and Material Contracts - This method relies on an agreement to pay for labor at a specified hourly rate and materials at cost plus a markup, with the final cost becoming clearer as the project progresses.
- Unit Price Contract - The contractor is paid based on the unit prices of each item of work performed after the design is finished, which means total costs emerge once quantities are defined post-design.
These methods contrast with lump-sum or fixed-price contracts where costs are determined before design is started. They require carefully managed engineering design process and often entail constructing prototypes and drawings that contribute to assessing the quality of a design. Mathematical models can be utilized early in the design process to provide rough cost estimates which are later refined and confirmed upon design completion.