建造工程合同所涉及的项目预算和成本估算（中英文）
BUDGET AND CONST ESTIMATE ON CONSTRUCTION
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.
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.
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.
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
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.
400 4-1 7 (201 207)(204)(204.1204.2 )4-1
Illustrative Set of Project Cost Accounts
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.
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.
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.
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.
Budget for a Design Office
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
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.
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 wi 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.
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.
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.
total cost.
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.
The actual
cost incurred to date is recorded in column 6 and can be derived
from the financial record keeping accounts.
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 fro 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
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.
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
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
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.
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:
􀁺 Units of
work completed.
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.
Incremental milestones.
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.
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
&Cost ratio.
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.
000/20 000=0.5 50%
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
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
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
1 000 (1 =0.304 8
/60 30 000
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:
400/1 000=0.4 40%40 000 /90 000
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
(380+200.9+50.6+0)=401 401
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.
40%40 000 /0.4=100 000
000-90 000)=10 000
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
1 000 500/400 60
/+30 000 =105 000
(105 000-90
000)=15 000 1.25 /0.25
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
5.1 5.1 A 40%60%40%50%60%-50%=10%
Estimation
Associated with Constructed Facilities
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.
capital cost for a construction project includes the expenses
related to the initial establishment of the facility:
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.
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.
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.
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:
Approaches
to Cost Estimation
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.
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.
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.
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
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
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.
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.
owner or its designated design professionals, the types of cost
estimates encountered run parallel with the planning and design as
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.
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.
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.
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 t
for detailed estimates, the level of detail can be quite
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
preliminary estimate is made on the basis of the layout of the
selected bridge form on the basis of the preliminary or conceptual
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.
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.
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.
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
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.
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
(budget estimate)
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.
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
已投稿到：
以上网友发言只代表其个人观点，不代表新浪网的观点或立场。