★Types of Estimates

An estimate can be prepared at any point in the life of a project. Estimates are developed early in the design process so that the owner and designer have cost information to guide the design. They are also developed during later stages of design to ensure that costs are within a given budget. During bidding, the owner uses estimates to check that the bids are a fair cost for the work. At bid time, the most extensive estimate is done by the contractor. This bid represents the actual costs as the project goes forward into construction. Estimates continue to be used during construction in case there are changes on the job or to help organize a specific set of activities.

A series of estimate types has been developed that serves each of these situations. Generally, estimates done in the later stages of design and during the bidding period are more accurate than ones done early.

Estimating during Design（设计阶段的估算）

Design estimates are important tools for the owner and the project management team as they develop the project’s scope of work. The discipline（原则） of providing cost information throughout the design phase makes cost a significant driver for the project team. Designers, in their passion（激情） to provide exciting solutions to the program, sometimes lose sight of the budget parameters（预算参数）. Owners can also get caught up in the excitement of desirable design features that in reality could compromise the budget or mean cutting the project in other areas. By providing cost information early and updating it throughout the project, cost professionals can keep the project team well grounded in（充分了解） the realities of cost.

Estimating during Construction（建造阶段的估算）

Once the design documents are complete, companies interested in actually performing the work price（对....出价） the project. Estimators working on this type of bid hope to win the job with the most competitive number while maintaining a reasonable profit for the company. This estimate is the most detailed of all estimate types and is also the most important. It carries with it legal implications（法律含义）. If its bid is accepted, a construction company is legally bound to a specific price for a specific scope of work. During the actual construction, however, there is give and take（赋予与接受） over the individual prices of each piece of the construction. The contractor must continually negotiate with suppliers and subcontractors over these prices throughout the procurement stage. If the contractor is a good negotiator and has priced the project with an adequate contingency（风险预备金）, then the final outcome should give the company a fair profit.

Especially on large complex projects, the scope of work is a continual focus of discussion between the contractor and the designer. No matter what type of contract is signed, someone is always at risk. Wherever that risk exists is where team members hotly debate about what is reasonable to include and what should be accepted as a change. The contractor can help this situation by listing any qualifications when the bid is submitted. Thus, discussions about the real scope of work can happen before there is any legal commitment regarding costs.

Many factors affecting costs lie outside the scope of work. There are owner requested changes, unforeseen conditions, and new regulatory requirements. These also must be priced as they emerge（出现）. Because the pricing established at bid time is done on a unit basis（单位为基础的）, it can help the contractor give information quickly to the owner about the cost impact of each change.

Detailed estimates take weeks to prepare and involve people from many different disciplines（学科）. A general contractor who is preparing a bid requests proposals from subcontractors , quantifies（报量） and prices（报价） work that will be done by his or her own workforce. Quotes（定额） from material suppliers  are used where possible to get precise material prices. When quotes cannot be obtained, contractors use company records and published cost data. Current wage rates and perceived worker productivity are figured into these costs. The estimator must, in essence, build the project on paper. Hypothetical（假设的） methods of construction; logistics of the site（现场的物流）, with its constraints for storage and maneuverability（存储和可操作性的限制）; delivery strategies; and the schedule of activities all must be understood before a realistic price can be assembled.