建造工程合同所涉及的项目预算和成本估算

PROJECT BUDGET AND CONST ESTIMATE ON CONSTRUCTION CONTRACT

 

For cost control on a project, the construction plan and the associated cash flow estimates can provide the baseline reference for subsequent project monitoring and control. For schedules, progress on individual activities can be compared with the project schedule to monitor the progress of activities. Contract and job specifications provide the criteria by which to assess and assure the required quality of construction. The final or detailed cost estimate provides a baseline for the assessment of financial performance during the project. To the extent that costs are within the detailed cost estimate, then the project is thought to be under financial control. Overruns in particular cost categories signal the possibility of problems and give an indication of exactly what problems are being encountered. Expense oriented construction planning and control focuses upon the categories included in the final cost estimation.

对于项目的成本控制、项目计划和相关的现金流量估算可以为后续的项目监督和控制提供参照基准。对于进度控制，可以将项目活动的实际进度和项目的计划进度进行比较，以监督项目的进度实施。合同和工作标准则为建设项目的质量提供了评价和保证准则。最终的或详细的成本预算为项目期的财务状况提供了评价基准。如果实际成本没有超出详细的成本估算，我们便认为项目的财务控制做得较好。特殊成本项次的超支发出了可能存在问题的信号，并且对所面临问题给出确切的指示。以费用为导向的建设项目计划和控制，侧重包含在最终成本估算内的成本项次。

 

For control and monitoring purposes, the original detailed cost estimate is typically converted to a project budget, and the project budget is used subsequently as a guide for management. Specific items in the detailed cost estimate become job cost elements. Expenses incurred during the course of a project are recorded in specific job cost accounts to be compared with the original cost estimates in each category. Thus, individual job cost accounts generally represent the basic unit for cost control. Alternatively, job cost accounts may be disaggregated or divided into work elements which are related both to particular scheduled activities and to particular cost accounts.

本着控制和监督的目的，初始的详细成本估算通常被转化为项目预算，并被用来作为随后成本管理的指南。详细成本估算中的具体项次成为工作成本要素。在项目实施过程中所发生的支出被记录在具体的工作成本报告中，以用来在每一成本项次下和原始成本估算相比较。这样一来，个别的工作成本报告通常就被称为成本控制的基本单位。同时，工作成本报告还可分解成与具体的进度活动及具体的成本报告都有关的作业要素。

 

In addition to cost amounts, information on material quantities and labor inputs within each job account is also typically retained in the project budget. With this information, actual materials usage and labor employed can be compared to the expected requirements. As a result, cost overruns or savings on particular items can be identified as due to changes in unit prices, labor productivity or in the amount of material consumed.

除了成本报告之外，项目预算中还应保留每项工作报告有关材料数量和劳动力投入的信息。有了这些信息，就可将实际的材料用量和人工消耗与预期的标准进行比较，这样就可以识别出具体活动成本超支或节约的原因，即是由于单价变化还是由于劳动生产率或材料消耗量上的变化所引起的。

 

The number of cost accounts associated with a particular project can vary considerably. For constructors, on the order of four hundred separate cost accounts might be used on a small project. These accounts record all the transactions associated with a project. Thus, separate accounts might exist for different types of materials, equipment use, payroll, project office, etc. Both physical and non-physical resources are represented, including overhead items such as computer use or interest charges. Table 4-1 summarizes a typical set of cost accounts that might be used in building construction. Note that this set of accounts is organized hierarchically, with seven major divisions (accounts 201 to 207) and numerous subdivisions under each division. This hierarchical structure facilitates aggregation of costs into pre-defined categories; for example, costs associated with the superstructure (account 204) would be the sum of the underlying subdivisions (ie. 204.1, 204.2, etc.). The sub-division accounts in Table 4-1 could be further divided into personnel, material and other resource costs for the purpose of financial accounting.

一个具体项目上的成本报告数字差异很大。对于建设项目，一个小项目也可能有多达400 多个独立的成本报告。这些报告记录了项目上的所有交易活动。因此，存在不同类型的专账，例如，有原材料报告、设备使用报告、工资报告、办公室报告等。同时，诸如计算机使用或利息支出之类的有形或无形的费用支出都要表示在报告当中。表4-1 总结了一套用在建设项目上的成本报告。注意，这套报告被划分为7 个主要部分(报告201 到报告207)，同时每部分又包括了大量子目。这种等级式的报告结构有利于把成本按预先确定好的类别进行汇总。例如，主体结构的成本(报告204)是由其下的各子项目汇总而来的(即204.1、204.2 等)。表4-1 中的子目报告又可进一步被分解成人工、材料和其他资源成本，以方便财务会计工作。

 

Illustrative Set of Project Cost Accounts 项目成本报告说明

In developing or implementing a system of cost accounts, an appropriate numbering or coding system is essential to facilitate communication of information and proper aggregation of cost information. Particular cost accounts are used to indicate the expenditures associated with specific projects and to indicate the expenditures on particular items throughout an organization. These are examples of different perspectives on the same information, in which the same information may be summarized in different ways for specific purposes. Thus, more than one aggregation of the cost information and more than one application program can use a particular cost account. Separate identifiers of the type of cost account and the specific project must be provided for project cost accounts or for financial transactions. As a result, a standard set of cost codes such as the MASTERFORMAT codes may be adopted to identify cost accounts along with project identifiers and extensions to indicate organization or job specific needs. Similarly the use of databases or, at a minimum, inter-communicating applications programs facilitate access to cost information.

在开发和运用成本报告系统时，适当的编码或译码体系有利于信息沟通和成本信息的汇总。特定的成本报告既可用来显示有关具体项目的费用，也可以显示组织中具体事项的开支，这就是相同的信息有不同角度应用的例子，即相同的信息因为特定的目的可以用不同的方法被计算和汇总。因而，一个成本报告可能被多个成本信息汇总应用程序所使用。具体项目中的项目成本报告或财务交易的每一类成本报告必须有独立的标识符。这样一来，就可以采用主格式编码这样一套标准成本编码，连同项目识别符来识别成本报告及显示组织或工作需求的工作范围。同样地，还可以通过使用数据库，或至少通过使用内部联络应用程序来进行成本信息的获取。

 

Converting a final cost estimate into a project budget compatible with an organization’s cost accounts is not always a straightforward task. Cost estimates are generally disaggregated into appropriate functional or resource based project categories. For example, labor and material quantities might be included for each of several physical components of a project. For cost accounting purposes, labor and material quantities are aggregated by type no matter for which physical component they are employed. For example, particular types of workers or materials might be used on numerous different physical components of a facility. Moreover, the categories of cost accounts established within an organization may bear little resemblance to the quantities included in a final cost estimate. This is particularly true when final cost estimates are prepared in accordance with an external reporting requirement rather than in view of the existing cost accounts within an organization.

把最终的成本估算转化成与组织的成本报告兼容的项目预算并不是一项简单的工作。成本估算通常被分解到基于项目范畴的功能或资源上。例如，项目的任何一个实体分部都会包括人工或材料的消耗量，从成本会计的角度出发，在统计人工和材料的消耗量时，是按照其类型而不考虑其具体被使用在哪个实体分部上。也就是说，同一类型的人工或材料可能在建筑产品的许多实体分部上都被使用过。此外，建立在组织内部的成本报告种类同详细的成本估算中的数量很少有相似之处。当详细的成本估算是按照外部的汇报要求而不是按照组织内部现有的成本报告来编制时，其情况就更加如此。

 

One particular problem in forming a project budget in terms of cost accounts is the treatment of contingency amounts. These allowances are included in project cost estimates to accommodate unforeseen events and the resulting costs. However, in advance of project completion, the source of contingency expenses is not known. Realistically, a budget accounting item for contingency allowance should be established whenever a contingency amount was included in the final cost estimate.

在按照成本报告来形成项目预算时所面临的一个具体问题是如何对待意外事件。为了应付不可预见事件和由此产生的成本，通常在项目成本估算中要安排一定数量的储备金。然而，在项目完工前，应急储备金的动用与否是根据意外事件是否发生来确定的。在实际操作当中，无论详细的成本估算中是否包括了意外事件，项目预算都应列支一笔应急储备金。

 

A second problem in forming a project budget is the treatment of inflation. Typically, final cost estimates are formed in terms of real dollars and an item reflecting inflation costs is added on as a percentage. This inflation allowance would then be allocated to individual cost items in relation to the actual expected inflation over the period for which costs will be incurred.

在形成项目预算时遇到的第二个问题是如何对待通货膨胀。典型地，详细成本估算是按照美元现价来编制的，同时追加一个以百分比形式出现的反应通货膨胀成本的列项，即通常所说的通货膨胀准备金。这笔通货膨胀准备金根据通货膨胀的实际发生水平所引发的成本被分配至各个具体的成本项目上。

 

Project Budget for a Design Office 设计项目的预算。

An example of a small project budget is shown in Table 4-2. This budget might be used by a design firm for a specific design project. While this budget might represent all the work for this firm on the project, numerous other organizations would be involved with their own budgets. In Table 4-2, a summary budget is shown as well as a detailed listing of costs for individuals in the Engineering Division. For the purpose of consistency with cost accounts and managerial control, labor costs are aggregated into three groups: the engineering, architectural and environmental divisions. The detailed budget shown in Table 4-2 applies only to the engineering division labor; other detailed budgets amounts for categories such as supplies and the other work divisions would also be prepared. Note that the salary costs associated with individuals are aggregated to obtain the total labor costs in the engineering group for the project. To perform this aggregation, some means of identifying individuals within organizational groups is required. Accompanying a budget of this nature, some estimate of the actual man-hours of labor required by project task would also be prepared. Finally, this budget might be used for internal purposes alone. In submitting financial bills and reports to the client, overhead and contingency amounts might be combined with the direct labor costs to establish an aggregate billing rate per hour.

一个小的项目预算示例见表 4-2。这是一个为具体项目进行设计的设计公司的预算。尽管这个预算涵盖了这家设计公司在项目上的所有工作，然而其他的组织也应有其自己的项目预算。在表4-2 当中，不但有一个汇总预算，同时还有一个设计部的人工费用明细表。为了成本报告的连续性和便于管理上的控制，人工费按设计部、建筑部和环境部 3 个部门来进行汇总。表4-2 中只列出了设计部的详细预算，而后勤等其他部门的详细预算理应同时列出，此表省略了。在设计部，总的劳动力成本是由为项目工作的所有人员的工资累加而得到的。为了完成这项工作，需要一些区分组织内部不同人员工资及绩效考评的方法，而通常我们会按项目各任务所需实际工时的估算来进行这项工作。最后，这个预算只能为组织内部的特定目标服务。在向客户提交财务单据和报告时，管理费和应急费在直接劳动力成本的基础上，以固定百分比汇总累加的形式出现。

 

For the purpose of project management and control, it is not sufficient to consider only the past record of costs and revenues incurred in a project. Good managers should focus upon future revenues, future costs and technical problems. For this purpose, traditional financial accounting schemes are not adequate to reflect the dynamic nature of a project. Accounts typically focus on recording routine costs and past expenditures associated with activities. Generally, past expenditures represent sunk costs that cannot be altered in the future and may or may not be relevant in the future. For example, after the completion of some activity, it may be discovered that some quality flaw renders the work useless. Unfortunately, the resources expended on the flawed construction will generally be sunk and cannot be recovered for re-construction (although it may be possible to change the burden of who pays for these resources by financial withholding or charges; owners will typically attempt to have constructors or designers pay for changes due to quality flaws). Since financial accounts are historical in nature, some means of forecasting or projecting the future course of a project is essential for management control. In this section, some methods for cost control and simple forecasts are described.

对于项目的管理和控制而言，仅考虑项目中已经发生了的成本和收益是不够的。好的项目经理还会关注未来成本、收益和一些技术问题。传统的财务会计计划无法反映出项目的动态特征，而只能集中在对日常性成本和已发生的各项工作开支的记录上。通常把过去已经发生且在未来无法再改变的支出称为“沉没成本”。例如，当某些工作完成后，有时会发现由于存在质量缺陷而使得产品毫无用处。遗憾的是，耗费在缺陷的建筑产品上的各种资源通常就“沉没了”，并且无法通过重建而得到恢复(尽管可以根据责任的归属来确定由谁承担所造成的损失，业主也会要求承包商或设计方来负担由于质量缺陷而产生的费用)。由于财务报告的历史局限性，为了进行有效的管理和控制，有必要使用一些预测和规划项目未来进程的方法和手段。下面将介绍一些有关成本控制和预测的方法。

 

An example of forecasting used to assess the project status is shown in Table 5-1. In this example, costs are reported in five categories, representing the sum of all the various cost accounts associated with each category.

一个用来预测和评价项目状况的例子见表 5-1。在这个例子当中，成本按5 个项次进行统计，每个项次再按不同口径进行汇总。

 

Budgeted cost. 预算成本。

The budgeted cost is derived from the detailed cost estimate prepared at the start of the project. Examples of project budgets were presented in above section. The factors of cost would be referenced by cost account.

预算成本由项目初始阶段的详细成本估算得来。项目预算的例子在上一部分已经介绍过。成本要素可参考成本报告。

 

Estimated total cost. 预计总成本。

The estimated or forecast total cost in each category is the current best estimate of costs based on progress and any changes since the budget was formed. Estimated total costs are the sum of cost to date, commitments and exposure. Methods for estimating total costs are described below.

每一项次的预计总成本是根据预算形成后项目的实际进展和变化对当前成本的最为精确的估算。预计总成本由完工成本、承诺成本和附加成本累加得到。估算总成本的方法将在下面介绍。

 

Cost to date. 完工成本。

The actual cost incurred to date is recorded in column 6 and can be derived from the financial record keeping accounts.

已完工的实际成本记录在表 5-1 的第6 栏里，它可由财务记录报告得到。

 

Over or Under. 超支或节约。

A final column in Table 5-1 indicates the amount over or under the budget for each category. This column is an indicator of the extent of variance from the project budget; items with unusually large overruns would represent a particular managerial concern. Note that variance is used in the terminology of project control to indicate a difference between budgeted and actual expenditures. The term is defined and used quite differently in statistics or mathematical analysis.

表 5-1 的最后一栏显示了每一项次预算超支或节约的数值，这一栏也是预算偏差的指示器。那些超出合理范围的成本偏差应当引起管理上的关注。注意，被用在项目控制中的“偏差”一词指的是预算值和实际值之间的差异。在统计学和数学分析中，这个术语的定义和使用是完全不同的。

 

In Table 5-1, labor costs are running higher than expected, whereas subcontracts are less than expected. The current status of the project is a forecast budget overrun of $ 5 950, with 23 percent of the budgeted project costs incurred to date.

在表5-1 中，人工成本比预期的高，而分包合同成本却比预期的低。项目目前的状况是预计总成本相对于预算成本超支 5 950 美元，同时完工成本占预算成本的比例为23%。

 

For project control, managers would focus particular attention on items indicating substantial deviation from budgeted amounts. In particular, the cost overruns in the labor and in the other expense category would be worthy of attention by a project manager in Table 5-1. A next step would be to look in greater detail at the various components of these categories. Overruns in cost might be due to lower than expected productivity, higher than expected wage rates, higher than expected material costs, or other factors. Even further, low productivity might be caused by inadequate training, lack of required resources such as equipment or tools, or inordinate amounts of re-work to correct quality problems. Review of a job status report is only the first step in project control.

从项目控制的角度而言，项目经理应对那些和预算成本有重大偏差的项次给予特殊的关注。具体地说，在表5-1 中，“人工”和其他两个项次都出现了超支的现象，应当引起注意。而下一步则要具体分析这些项次的不同组成部分的具体情况。例如，成本的超支可能是由于劳动生产率的降低、工资的提高、材料涨价或其他原因等引起的。进一步讲，劳动生产率的降低又有可能源于新来的工人未经培训、缺乏机器和设备等生产所需的资源、纠正质量问题的重复工作不当等原因。分析工作状况报告只是项目控制的第一步。

 

The job status report illustrated employs explicit estimates of ultimate cost in each category of expense. These estimates are used to identify the actual progress and status of an expense category. Estimates might be made from simple linear extrapolations of the productivity or cost of the work to date on each project item.

工作状况报告对每一个费用项次都给出了较为精确的最终成本估算。这个估算被用来判别项目的实际进展和某成本项次的状况。这个估算值可以用每一项次的劳动生产率或完工成本进行简单的线性推演得到。

 

In addition to changes in productivities, other components of the estimating formula can be adjusted or substituted. For example, the change in unit prices due to new labor contracts or material supplier’s prices might be reflected in estimating future expenditures. In essence, the same problems encountered in preparing the detailed cost estimate are faced in the process of preparing exposure estimates, although the number and extent of uncertainties in the project environment decline as work progresses. The only exception to this rule is the danger of quality problems in completed work which would require re-construction.

除了生产率的变化之外，预测方程中的其他组成部分也可以进行替换或调整。例如，由于新的劳动合同或材料价格所引起的单元上的变化也可以在预测总成本中得以反映。实际上，在计算附加成本时也会遇到同样的问题，尽管随着项目的不断进展，项目当中不确定性的量和度都呈下降趋势。这个规则的唯一例外是完工产品因为严重质量问题而需返修重建的情形。

 

Each of the estimating methods described above require current information on the state of work accomplishment for particular activities. There are several possible methods to develop such estimates, including:

上面所介绍的每一种预测方法都需要具体工作的劳动量完成状态信息。下面的几种方法有助于进行成本的预测。

 

􀁺 Units of work completed. 完工劳动单元。

For easily measured quantities the actual proportion of completed work amounts can be measured. For example, the linear feet of piping installed can be compared to the required amount of piping to estimate the percentage of piping work completed.

对于易于测量的劳动数量，可直接得到实际完工劳动量占总劳动量的比例。例如，将已安装的直线管道和需要安装的管道数量进行比较便可测算出已完工管道劳动量的百分比。

 

Incremental milestones. 里程碑累计

Particular activities can be sub-divided or “decomposed” into a series of milestones, and the milestones can be used to indicate the percentage of work complete based on historical averages. For example, the work effort involved with installation of standard piping might be divided into four milestones.

某项具体工作可被分解成一系列的里程碑，而这些里程碑可用来显示完工劳动量基于历史平均值的百分比。例如，某标准管道安装工作的劳动可被划分为如下4 个里程碑。

 

Subjective judgments of the percentage complete can be prepared by inspectors, supervisors or project managers themselves. Clearly, this estimated technique can be biased by optimism, pessimism or inaccurate observations. Knowledgeable estimaters and adequate field observations are required to obtain sufficient accuracy with this method.

对于完工百分比的主观判断可由监督方、监理方或项目经理自己做出。显然，由于乐观、悲观或观察不够细致等主观原因，会使上面所做出的判断有所偏颇。因此，使用这种方法要想保证相当的准确性，就要求预测者不但具有丰富的知识，还应有足够的现场观察。

 

 Cost ratio. 成本率。

The cost incurred to date can also be used to estimate the work progress. For example, if an activity was budgeted to cost $20 000 and the cost incurred at a particular date was $10 000, then the estimated percentage complete under the cost ratio method would be 10 000/20 000 = 0.5 or fifty percent. This method provides no independent information on the actual percentage complete or any possible errors in the activity budget: the cost forecast will always be the budgeted amount. Consequently, managers must use the estimated costs to complete an activity derived from the cost ratio method with extreme caution.

完工成本也能用来预测工作进度。例如，如果某工作的预算成本为20 000 美元而截止某特定日期已发生的成本为10 000 美元，那么用成本率来表示预测完工百分率就是10 000/20 000=0.5 或50%。然而，用这种方法来准确地反映工作实际完工比例还需依靠其他信息，并且会产生工作预算上的一些错误，因为在这里，预测成本始终等于预算成本。因此，项目经理在用成本率导出的预测成本来完成某工作时必须极其审慎。

 

Systematic application of these different estimating methods to the various project activities enables calculation of the percentage complete or the productivity estimates used in preparing job status reports.

通过对各种项目工作系统地运用不同的预测方法，可以计算出工作状况报告要用到的完工百分比和生产率的估算值。

 

In some cases, automated data acquisition for work accomplishments might be instituted. For example, transponders might be moved to the new work limits after each day’s activity and the new locations automatically computed and compared with project plans. These measurements of actual progress should be stored in a central database and then processed for updating the project schedule.

在有些情况下，需要构建一个自动读取完工数据的系统。例如，在当天工作完成之后，读取器会自动移向新的工作表及其地址进行运算并和项目计划进行比较。项目的实际进度会被存储到中央数据库中，经过处理后用以更新项目计划。

 

Suppose that we wish to estimate the total cost to complete piping construction activities on a project. The piping construction involves 1 000 linear feet of piping which has been divided into 50 sections for management convenience. At this time, 400 linear feet of piping has been installed at a cost of $40 000 and 500 man-hours of labor. The original budget estimate was $90 000 with a productivity of one foot per man-hour, a unit cost of $60 per man hour and a total material cost of $ 30 000. Firm commitments of material delivery for the $30 000 estimated cost have been received.

假定欲估算某项目直线管道铺设工程的总成本。该管道工程是总长为 1 000 英尺(1 英尺=0.304 8 米)的直线管道铺设，为了方便管理被划分成50 段。此时，已有400 英尺的直线管道以40 000 美元的成本和500 人工时的劳动力进行了铺设。初始预算约为90 000 美元，其中生产率为1 英尺/工时，每工时的单位成本为60 美元，且总的材料成本为30 000 美元。材料的运输已得到保证。

 

The first task is to estimate the proportion of work completed. First, 400 linear feet of pipe is in place out of a total of 1 000 linear feet, so the proportion of work completed is 400/1 000 = 0.4 or 40%. This is the “units of work completed” estimation method. Second, the cost ratio method would estimate the work complete as the cost-to-date divided by the cost estimate or $40 000/$ 90 000 = 0.44 or 44%.Third, the “incremental milestones” method would be applied by examining each pipe section and estimating a percentage complete and then aggregating to determine the total percentage complete. For example, suppose the following quantities of piping fell into four categories of completeness:

第一项工作是估算完工劳动的比例。首先，已对总长度为 1 000 英尺的直线管道中的400 英尺进行了铺设，所以已完工劳动的百分比为400/1 000=0.4 或40%。这里用到的是完工劳动单元估算法。其次，用成本率法来估算完工劳动率，即用完工成本除以估算成本，亦即40 000 美元/90 000 美元=0.44 或44%。最后，用“里程碑累计”法来核对管道的每一分项工程，估算其完工百分比并进行逐项累计，以确定总完工百分比。例如，假定把管道工程的完成按4 个类别进行划分。

 

Then using the incremental milestones shown above, the estimate of completed work would be 380 + 20×0.9 + 5×0.6 + 0 = 401 ft and the proportion complete would be 401 ft/1 000 ft =0.401 or 40% after rounding.

根据上面的里程碑累计，完工劳动的估算应当为(380+20×0.9+5×0.6+0)英尺=401 英尺，完工比例为401 英尺/1 000 英尺=0.401，或近似取0.4。

 

Once an estimate of work completed is available, then the estimated cost to complete the activity can be calculated. First, a simple linear extrapolation of cost results in an estimate of $40 000/0.4 = $100 000 for or the piping construction using the 40% estimate of work completed.

一旦得到了完工劳动量的估算值，就可以进行工作完工成本的计算。首先，由于管道工程已完成了约40%，所以用线性推演得到的预计成本为40 000 美元/0.4=100 000 美元。这意味着按当前状态项目将会出现(100 000-90 000)美元=10 000 美元的成本超支。

 

This estimate projects a cost overrun of 100 000-90 000 = $10 000.Second, a linear extrapolation of productivity results in an estimate of (1 000 ft)(500 hrs/400 ft)($60/hr) + 30 000 = $105 000 for completion of the piping construction. This estimate suggests a variance of 105 000-90 000 = $15 000 above the activity estimate. The source of the variance can also be identified in this calculation: compared to the original estimate, the labor productivity is 1.25 hours per foot or 25% higher than the original estimate.

其次，如果用生产率进行线性推演，可得管道工程的完工估算成本为1 000 英尺×500小时/400 英尺×60 美元/小时+30 000 美元=105 000 美元。在这种情况下，预计有(105 000-90 000)美元=15 000 美元的成本偏差。偏差的原因也可以理解为和初始估算相比，劳动生产率为1.25 小时/英尺或比初始估算中的劳动生产率在每英尺管道上多用了0.25 小时。

 

The forecasting procedures described above assumed linear extrapolations of future costs, based either on the complete experience on the activity or the recent experience. For activities with good historical records, it can be the case that a typically non-linear profile of cost expenditures and completion proportions can be estimated. Figure 5.1 illustrates one possible non-linear relationships derived from experience in some particular activity. For example, point A in Figure 5.1 suggests a higher expenditure than is normal for the completion proportion. This point represents 40% of work completed with an expenditure of 60% of the budget. Since the historical record suggests only 50% of the budget should be expended at time of 40% completion, a 60%-50%=10% overrun in cost is expected. If comparable cost overruns continue to accumulate, then the cost-to-complete will be even higher.

上例中的预测程序是在对工作有完全的或近期的经验基础上，用线性方法来推断未来的成本。而对有些历史数据完整的工作，即使数据之间成非线性关系，仍可预测其成本超支和完工百分比。图5.1 所示为成本和完工百分比呈非线性关系的某工作。例如，图5.1 中的A 点表示在对应的完工百分比上其成本却有所超支，即在该点劳动量完成了40%，但成本支出却占到了预算成本的60%。而根据历史统计，当劳动量完成40%时，成本支出应占预算成本的50%，因此出现了60%-50%=10%的成本偏差。如果这种可比的成本超支继续累计下去，那么完工成本将变高。

 

Cost Estimation成 本 估 算

Costs Associated with Constructed Facilities与建筑设施相关的成本

The costs of a constructed facility to the owner include both the initial capital cost and the subsequent operation and maintenance costs. Each of these major cost categories consists of a number of cost components.

对业主来说，一项建筑设施的成本包括初始投资和随后的运行与养护费用。这两大项费用又是由许多分项费用组成的。

 

The capital cost for a construction project includes the expenses related to the initial establishment of the facility:

对于一个建设项目，其初始投资包括与建设该设施相关的各项资本投入：

 

The magnitude of each of these cost components depends on the nature, size and location of the project as well as the management organization, among many considerations. The owner is interested in achieving the lowest possible overall project cost that is consistent with its investment objectives.

以上这些费用的多少要由项目的性质、规模和地理位置，以及管理组织等多方面的因素来决定。业主总希望以尽可能少的投入来实现项目的目标。

 

It is important for design professionals and construction managers to realize that while the construction cost may be the single largest component of the capital cost, other cost components are not insignificant. For example, land acquisition costs are a major expenditure for building construction in high-density urban areas, and construction financing costs can reach the same order of magnitude as the construction cost in large projects such as the construction of nuclear power plants.

设计者和施工管理者应当非常明确的重要一点是，施工建设费用是成本中最主要的一项费用，但是其他费用也不可忽视。例如，在高密度建筑的市区建设一个项目，取得土地的费用是一项主要的成本，而对核电站等这样的大型项目建设，融资成本可能与项目的建造成本基本持平。

 

From the owner’s perspective, it is equally important to estimate the corresponding operation and maintenance cost of each alternative for a proposed facility in order to analyze the life cycle costs. The large expenditures needed for facility maintenance, especially for publicly owned infrastructure, are reminders of the neglect in the past to consider fully the implications of operation and maintenance cost in the design stage.

站在业主方的角度看，为了分析项目全寿命周期的成本，对每个建设方案的运行和维护成本进行估计是同样重要的。有些项目，尤其是公共项目的物业保养成本巨大，这时刻都在提醒我们，不该像过去那样在项目的设计阶段忽视项目建成后的运行和保养。

 

In most construction budgets, there is an allowance for contingencies or unexpected costs occurring during construction. This contingency amount may be included within each cost item or be included in a single category of construction contingency. The amount of contingency is based on historical experience and the expected difficulty of a particular construction project. For example, one construction firm makes estimates of the expected cost in five different areas:

在很多项目的预算中，总有一部分不可预见的费用准备用于施工中的意外情况，这些不可预见费用有可能包含在每一项费用中，也可能作为一项总的不可预见费用。不可预见费用的多少可根据历史经验和特定项目的建设难度来估计。例如，某一建筑公司对不可预见费用的估算包括5 个不同方面。

 

Approaches to Cost Estimation成本估算的方法

Cost estimating is one of the most important steps in project management. A cost estimate establishes the base line of the project cost at different stages of development of the project. A cost estimate at a given stage of project development represents a prediction provided by the cost engineer or estimator on the basis of available data. According to the American Association of Cost Engineers, cost engineering is defined as that area of engineering practice where engineering judgment and experience are utilized in the application of scientific principles and techniques to the problem of cost estimation, cost control and profitability. Virtually all cost estimation is performed according to one or some combination of the following basic approaches.

成本估算是项目管理中最重要的环节之一。它在项目建设的不同阶段为项目的成本建立了一条基准线。在项目开发过程中的某一特定阶段的成本估算就是造价工程师在现有数据基础上对未来成本的预测。根据美国造价工程师协会的定义，工程估价是运用科学理论和技术，根据工程师的判断和经验，解决成本估算、成本控制和盈利能力等问题的活动。实际上，所有的估价活动都是基于以下这些基本方法中的一种或几种方法的组合。

 

(1) Production function. In microeconomics, the relationship between the output of a process and the necessary resources is referred to as the production function. In construction, the production function may be expressed by the relationship between the volume of construction and a factor of production such as labor or capital. A production function relates the amount or volume of output to the various inputs of labor, material and equipment. For example, the amount of output Q may be derived as a function of various input factors x1, x2,…, xn by means of mathematical and/or statistical methods. Thus, for a specified level of output, we may attempt to find a set of values for the input factors so as to minimize the production cost. The relationship between the sizes of a building project (expressed in square feet) to the input labor (expressed in labor hours per square foot) is an example of a production function for construction.

(1) 产出函数。在微观经济学中把过程的产出和资源的消耗这两者之间的关系叫做产出函数。在建筑工程中，产出函数则可认为是建设项目的规模和生产参数(如人工或资金)之间的关系。产出函数建立了产出的总量或规模与各种投入(比如人力、材料、设备)之间的关系。例如，代表产出的Q 可以用代表各种投入的不同参数x1, x2, …, xn 等通过数学和/或统计方法表达。因此，对某一特定的产出，可以通过对各个投入参数赋予不同的值，从而找到一个最低的生产成本。房屋建筑的大小(用平方英尺表示)和消耗的人力(用小时/平方英尺来表示)之间的关系就是产出函数的一个例子。

 

(2) Empirical cost inference. Empirical estimation of cost functions requires statistical techniques which relate the cost of constructing or operating a facility to a few important characteristics or attributes of the system. The role of statistical inference is to estimate the best parameter values or constants in an assumed cost function. Usually, this is accomplished by means of regression analysis techniques.

(2) 经验成本推论法。利用基于经验的成本函数估算成本需要一些统计技术，这些技术将建造或运营某设施与系统的一些重要特征或属性联系起来。数理统计推理的目的是为了找到最适合的参数值或者常数，用于在假定的成本函数中进行成本估算。在通常情况下，这需要利用回归分析法。

 

(3) Unit costs for bill of quantities. A unit cost is assigned to each of the facility components or tasks as represented by the bill of quantities. The total cost is the summation of the products of the quantities multiplied by the corresponding unit costs. The unit cost method is straightforward in principle but quite laborious in application. The initial step is to break down or disaggregate a process into a number of tasks. Collectively, these tasks must be completed for the construction of a facility. Once these tasks are defined and quantities representing these tasks are assessed, a unit cost is assigned to each and then the total cost is determined by summing the costs incurred in each task. The level of detail in decomposing into tasks will vary considerably from one estimate to another.

(3) 用于工程量清单的单位成本法。由工程量清单表达的各项任务或各个组成部分的单位成本能够明确，总成本就是各项产品的数量与其相应单位成本的乘积之和。单位成本法虽然在理论上非常直接，但是难以应用。第一步是将某工作分解成许多项任务，当然每项任务都是为项目建设服务的。一旦这些任务确定，并有了工作量的估算，用单价与每项任务的量相乘就可以得到每项任务的成本，从而得出每项工作的成本。当然，在不同的估算中对每项工作分解的详细程度可能会有很大差别。

 

(4) Allocation of joint costs. Allocations of cost from existing accounts may be used to develop a cost function of an operation. The basic idea in this method is that each expenditure item can be assigned to particular characteristics of the operation. Ideally, the allocation of joint costs should be causally related to the category of basic costs in an allocation process. In many instances, however, a causal relationship between the allocation factor and the cost item cannot be identified or may not exist.

(4) 混合成本分配法。有时候要从现有的会计账目上去分解，从而确定某项具体操作的成本函数。这种方法的基本思想是，每一项花费都能够对应地分配到操作过程中的某一特定步骤。理想情况是在成本分配过程中，混合成本能够有因果对应关系地被分解，并确定为某种基本成本。但是，在很多情况下，子项目和其分配成本之间难以确定或者根本不存在因果关系。

 

Construction cost constitutes only a fraction, though a substantial fraction, of the total project cost. However, it is the part of the cost under the control of the construction project manager. The required levels of accuracy of construction cost estimates vary at different stages of project development, ranging from ball park figures in the early stage to fairly reliable figures for budget control prior to construction. Since design decisions made at the beginning stage of a project life cycle are more tentative than those made at a later stage, the cost estimates made at the earlier stage are expected to be less accurate. Generally, the accuracy of a cost estimate will reflect the information available at the time of estimation.

建造成本是整个项目成本中的一部分，虽然很重要，但只是施工项目经理控制下的成本的一部分。在项目建设的不同阶段对估价精确度的要求也不一样，早期只是粗略估计，到施工前的预算就应当是相当可靠了。由于在项目生命周期早期设计方面的决策比后期更加具有不确定性，所以也就不能期望早期阶段的估价会准确。总的来说，估价的准确程度将反映估价时所获取的信息。

 

Construction cost estimates may be viewed from different perspectives because of different institutional requirements. In spite of the many types of cost estimates used at different stages of a project, cost estimates can best be classified into three major categories according to their functions. A construction cost estimate serves one of the three basic functions: design, bid and control. For establishing the financing of a project, either a design estimate or a bid estimate is used.

由于不同机构的要求不同，对建造成本估算也存在不同的观点。虽然在项目的不同阶段，建造成本的估算有许多不同的方法，但是根据其功用可分为3 种主要方法。建造成本估算主要服务于以下3 个方面：设计、投标和控制。要对项目进行融资，要么需要设计估价，要么需要投标估价。

 

For the owner or its designated design professionals, the types of cost estimates encountered run parallel with the planning and design as follows:

对于业主或他指定的设计者而言，在规划和设计过程中要平行进行的估价的种类如下：

 

In the planning and design stages of a project, various design estimates reflect the progress of the design. At the very early stage, the screening estimate or order of magnitude estimate is usually made before the facility is designed, and must therefore rely on the cost data of similar facilities built in the past. A preliminary estimate or conceptual estimate is based on the conceptual design of the facility at the state when the basic technologies for the design are known.

在项目的规划和设计阶段，不同的设计估算反映了设计进展的不同阶段。在最初阶段，投资匡算或者宏观估价通常是在项目设计之前做出的，因此必须依靠过去类似项目的数据。初步估算或者称为概念方案阶段估价主要基于概念设计方案进行估算，此时只明确了最基本的技术方案。

 

The detailed estimate or definitive estimate is made when the scope of work is clearly defined and the detailed design is in progress so that the essential features of the facility are identifiable.

The engineer’s estimate is based on the completed plans and specifications when they are ready for the owner to solicit bids from construction contractors. In preparing these estimates, the design professional will include expected amounts for contractors’ overhead and profits.

详细估算或者称为明确估价是在工程范围基本明确、详细设计正在进行、项目的基本特征已经确定时做出的。工程师估算要以明确的施工计划和施工说明为基础，并且业主也可以据此发包选择施工承包商。在做这些估算时，设计人员应将承包商的日程管理费和利润考虑进去。

 

The costs associated with a facility may be decomposed into a hierarchy of levels that are appropriate for the purpose of cost estimation. The level of detail in decomposing the facility into tasks depends on the type of cost estimate to be prepared. For conceptual estimates, for example, the level of detail in defining tasks is quite coarse; for detailed estimates, the level of detail can be quite fine.

为了进行成本估算，可以把一项设施的有关成本分解成几个适当的层次。层次划分的详细程度取决于成本估算的种类，例如，对于概念设计方案阶段的估价，层次的划分就比较粗，而对于详细设计阶段的估价，层次的划分就应该很细。

 

As an example, consider the cost estimates for a proposed bridge across a river. A screening estimate is made for each of the potential alternatives, such as a tied arch bridge or a cantilever truss bridge. As the bridge type is selected, e.g. the technology is chosen to be a tied arch bridge instead of some new bridge form; a preliminary estimate is made on the basis of the layout of the selected bridge form on the basis of the preliminary or conceptual design.

例如，要对某条河上的拟建桥梁进行造价估算，投资匡算是对每个潜在的方案进行估算，如是采用拱桥方案还是悬臂桁架桥方案。当桥的类型确定后，比如选定拱形桥而不是其他形式的桥，这时就要基于拱形桥的平面布置，在初步或概念设计的基础上做初步估算。

 

When the detailed design has progressed to a point when the essential details are known, a detailed estimate is made on the basis of the well defined scope of the project. When the detailed plans and specifications are completed, an engineer’s estimate can be made on the basis of items and quantities of work.

当详细设计进行到一定阶段，最根本的详细设计已经完成时，就要基于项目的明确范围进行详细估算。当完成了详细施工计划和施工指导说明后，就可以根据各项工作和其工程量进行工程师估算了。

 

For the contractor, a bid estimate submitted to the owner either for competitive bidding or negotiation consists of direct construction cost including field supervision, plus a markup to cover general overhead and profits. The direct cost of construction for bid estimates is usually derived from a combination of the following approaches.

对于承包商来说，提交给业主的投标估价的目的是为竞争的需要或者是与业主谈判的需要，投标估价中包括直接施工成本(包括现场监督以及在此基础上增加一笔总体管理费)和利润。用于投标估价中的直接施工成本常用以下几种方法组合计算：

 

The contractor’s bid estimates often reflect the desire of the contractor to secure the job as well as the estimating tools at its disposal. Some contractors have well established cost estimating procedures while others do not. Since only the lowest bidder will be the winner of the contract in most bidding contests, any effort devoted to cost estimating is a loss to the contractor who is not a successful bidder. Consequently, the contractor may put in the least amount of possible effort for making a cost estimate if it believes that its chance of success is not high.

承包商的投标估价常常反映了承包商对完成投标工程的期望值，也反映了其所采用的估价工具。有些承包商拥有良好的估价程序，而有些则没有。由于在大多数工程招标中一般都是最低价中标，所以对于未中标者来说，在投标估价过程中的任何投入都是浪费。因此，如果一个承包商认为自己胜出的机会不是很大，他就会花费尽可能少的精力来进行成本估价。

 

If a general contractor intends to use subcontractors in the construction of a facility, it may solicit price quotations for various tasks to be subcontracted to specialty subcontractors. Thus, the general subcontractor will shift the burden of cost estimating to subcontractors. If all or part of the construction is to be undertaken by the general contractor, a bid estimate may be prepared on the basis of the quantity takeoffs from the plans provided by the owner or on the basis of the construction procedures devised by the contractor for implementing the project.

如果一个总承包商在设施的建设过程中希望将工程进行分包，他有可能要求各个专业分包商提交分包报价单，所以总承包商将把成本估算的任务转移到分包商头上。如果所有的工程或部分工程由总承包商来施工，投标估计就要根据业主提出的计划和工程量或由承包商提供的施工组织计划来进行编制。

 

For example, the cost of a footing of a certain type and size may be found in commercial publications on cost data which can be used to facilitate cost estimates from quantity takeoffs. However, the contractor may want to assess the actual cost of construction by considering the actual construction procedures to be used and the associated costs if the project is deemed to be different from typical designs. Hence, items such as labor, material and equipment needed to perform various tasks may be used as parameters for the cost estimates.

例如，某类房屋某种基础的成本可以从某些商业出版物中找到其单价，再根据工程量就可以算出成本。但是，项目的实际情况可能导致实际施工程序与一般设计要求不同，在这种情况下承包商就要想办法估算其真实的成本和相关的费用。因此，为完成不同任务所需要的劳动力、材料和设备等就应该作为成本估算的参数。

 

Both the owner and the contractor must adopt some base line for cost control during the construction. For the owner, a budget estimate must be adopted early enough for planning long term financing of the facility. Consequently, the detailed estimate is often used as the budget estimate since it is sufficient definitive to reflect the project scope and is available long before the engineer’s estimate.

在施工过程中，业主和承包商都会有一个成本的基准来控制实际成本。对业主来说，必须尽早明确预算(budget estimate)用于项目的长期财务规划。因而，在工程师估算完成前的相当长时间里，只能用详细估算来作为控制预算，因为详细估算也能充分明确地反映项目的范围。

 

As the work progresses, the budgeted cost must be revised periodically to reflect the estimated cost to completion. A revised estimated cost is necessary either because of change orders initiated by the owner or due to unexpected cost overruns or savings.

在工程进行的过程中，必须对成本估算进行定期更新，以反映完工前的预测成本。由于在施工中业主可能提出变更要求，或者有不可预见的突破成本或节约成本的情况发生，对成本估算进行及时更新是很必要的。

 

For the contractor, the bid estimate is usually regarded as the budget estimate, which will be used for control purposes as well as for planning construction financing. The budgeted cost should also be updated periodically to reflect the estimated cost to completion as well as to insure adequate cash flows for the completion of the project.

对承包商来说，经常用投标估价作为预算，既可以进行成本控制，也可以进行施工期间的财务规划。该预算成本也要定期更新，以反映完工前的预测成本，并确保项目完工前的现金投入。