Chapter 3 Discussion Questions (Continued)
4.2 BIM APPLICATION AREAS FOR OWNERS
4.2.1 Cost Reliability and Management
Owners are often faced with cost overruns or unexpected costs that force them to either “ value engineer, ” go over budget, or cancel the project. Surveys of owners indicate that up to two - thirds of construction clients report cost over- runs (Construction Clients Forum 1997; FMI/CMAA 2005, 2006). To mitigate the risk of overruns and unreliable estimates, owners and service providers add contingencies to estimates or a “ budget set aside to cope with uncertainties during construction ” (Touran 2003). Figure 4 - 2 shows a typical range of contingencies that owners and their service providers apply to estimates, which vary from 50% to 5% depending on the project phase. Unreliable estimates expose owners to signifi cant risk and artifi cially increase all project costs.
The reliability of cost estimates is impacted by a number of factors, including market conditions that change over time, the time between estimate and execution, design changes, and quality issues (Jackson 2002). The accu- rate and computable nature of building information models provides a more reliable source for owners to perform quantity take - off and estimating and provides faster cost feedback on design changes. This is important because the ability to infl uence cost is highest early in the process at the conceptual and feasibility phase, as shown in Figure 4 - 3 . Estimators cite insuffi cient time, poor documentation, and communication breakdowns between project participants, specifi cally between owner and estimator, as the primary causes of poor estimates (Akintoye and Fitzgerald 2000).
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Book section
Specifi c BIM application areas for Owner (referenced in
this Chapter) Market Driver
Benefi ts to all Owners
Relevant case study (CS) or reference Chapter 5:
designers and engineers
Space planning and program compliance
Cost management marketplace complexity
Ensure project requirements are met
Coast Guard Facility Planning
Federal Courthouse Energy
( environmental) analysis
Sustainability Improve sustainability and energy
effi ciencies
Federal Offi ce Building
Design confi guration/
scenario planning
Cost management complexity
Design quality communication
Coast Guard Facility Planning
Building system analysis/simulation
Sustainability Building performance and quality
National Aquatics Center
Design communication/
review
Marketplace complexity and language barriers
Communication All case studies
Chapters 5 and 6:
designers, engineers, contractors
Quantity take-off and cost estimation
Cost management More reliable and accurate estimates
Hillwood Commercial Project
Penn National Parking Structure
100 11th Ave.
Apartments Design coordination
(clash detection)
Cost management and infrastructure complexity
Reduce fi eld errors and reduce construction costs
Camino Medical Building
Chapters 6 and 7:
contractors and fabricators
Schedule simulation/
4D
Time to market, labor shortages, and language barriers
Communicate schedule visually
One Island East Offi ce Tower
Project controls Time to market Track project activities GM Flint project Pre-fabrication Time to market Reduce onsite labor
and improve design quality
Camino Medical Building 100 11th Ave.
Apartments Chapter 4:
owners
Pro forma analysis Cost management Improve cost reliability Hillwood Commercial Project
Operation simulation Sustainability/Cost management
Building performance and maintainability Asset management Asset management Facility and asset
management
Coast Guard Facility Planning
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Owners can manage cost with BIM applications to provide:
More reliable estimates early in the process with conceptual BIM estimating. Estimates that use conceptual building information models consisting of components with historical cost information, productivity infor- mation, and other estimating information can provide owners with quick feedback on various design scenarios. Accurate estimates can be very valuable early in the project, particularly for assessing a project ’ s predicted cash fl ow and procuring fi nance. The Hillwood Commercial project case study demonstrates how owners working with a service provider employing a conceptual BIM - based
FIGURE 4-3 Infl uence of overall project cost over the project lifecycle.
Today’s use of BIM is typically limited to the late phase of design and engineering or early phases of construction.
Use of BIM earlier in design process will have greater infl uence on cost. Improving overall cost reliability is a key motivator for employing BIM-based cost estimating methods.
Level of Influence on Cost
Start
Conceptual planning/feasibility
studies
Design and engineering
Procurement and construction
Startup
Operation and maintenance 0%
100%
Project Time
Ability to influence costs Construction cost
0%
100%
Emerging uses of BIM with examples in Chapter 9 Case Studies
More common applications of BIM with examples in Chapter 9 Case Studies
Contingency/Reliability as a Function of Project Phases
0 10 20 30 40 50 60
Preliminary Estimate
Budget Estimate
Final Design Estimate
Actual Stage of Estimate Development
% Reliability/Contingency
Upper Limit Lower Limit BIM
FIGURE 4-2 Chart showing the upper and lower limits that an owner typically adds to the contingency and reliability of an estimate over different phases of a project (data adapted from United States 1997; Munroe 2007;
Oberlander and Trost 2001) and the potential targeted reliability improvements associated with BIM- based estimating.
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estimating tool called DProfi ler are able to reduce overall contingency and reli- ability and ultimately save money by borrowing less.
Faster, better detailed, and more accurate estimates with BIM quantity take - off tools. Both owners and estimators struggle with the ability to respond to design and requirement changes and understand the impact of those changes on the overall project budget and estimate. By linking the design model with the estimating processes, the project team can speed up the quantity take - off and overall estimating process and get faster feedback on proposed design changes (see Chapters 5 and 6 ). For example, owners can automatically derive accurate quantities and in turn streamline and verify estimates of designers and subcontractors (Rundell 2006). The Hillwood Commercial project case study cites evidence that estimating with BIM early in design can result in a 92% time reduction to produce the estimate with only a 1% variance between the manual and BIM - based processes. In the One Island East Offi ce Tower case study, the owner was able to set a lower contingency in their budget as a result of the reli- ability and accuracy of the BIM - based estimate.
Owners, however, must realize that BIM - based takeoff and estimating is only a fi rst step in the whole estimating process; it does not thoroughly address the issue of omissions. Additionally, the more accurate derivation of components that BIM provides does not deal with specifi c site conditions or the complexity of the facility, which depend on the expertise of an estimator to quantify.