Design-Bid-Build

Design-Bid-Build

A signifi cant percentage of buildings are built using the Design-Bid-Build (DBB)

approach (almost 90 percent of public buildings and about 40 percent of private

buildings in 2002) (DBIA 2007). The two major benefi ts of this approach are:

more competitive bidding to achieve the lowest possible price for an owner; and

less political pressure to select a given contractor. (The latter is particularly

important for public projects.) Figure 1–2 schematically illustrates the typical

DBB procurement process as compared to the typical Construction Management at Risk (CM at Risk) and Design-Build (DB) processes (see Section 1.2.2)

In the DBB model, the client (owner) hires an architect, who then develops a

list of building requirements (a program) and establishes the project’s design

objectives. The architect proceeds through a series of phases: schematic

design, design development, and contract documents. The final documents

must fulfill the program and satisfy local building and zoning codes. The

architect either hires employees or contracts consultants to assist in designing

structural, HVAC, piping, and plumbing components. These designs are

recorded on drawings (plans, elevations, 3D visualizations), which must then

be coordinated to refl ect all of the changes as they are identifi ed. The final

set of drawings and specifi cations must contain suffi cient detail to facilitate

construction bids. Because of potential liability, an architect may choose to

include fewer details in the drawings or insert language indicating that the

drawings cannot be relied on for dimensional accuracy. These practices often

lead to disputes with the contractor, as errors and omissions are detected and

responsibility and extra costs reallocated.

Stage two involves obtaining bids from general contractors. The owner

and architect may play a role in determining which contractors can bid. Each

contractor must be sent a set of drawings and specifi cations which are then

used to compile an independent quantity survey. These quantities, together

with the bids from subcontractors, are then used to determine their cost

estimate. Subcontractors selected by the contractors must follow the same

process for the part of the project that they are involved with. Because of

the effort required, contractors (general and subcontractors) typically spend

approximately 1 percent of their estimated costs in compiling bids.1 If a

contractor wins approximately one out of every 6 to 10 jobs that they bid on,

the cost per successful bid averages from 6 to 10 percent of the entire project

cost. This expense then gets added to the general and subcontractors’ overhead costs.

The winning contractor is usually the one with the lowest responsible bid,

including work to be done by the general contractor and selected subcontractors. Before work can begin, it is often necessary for the contractor to redraw

some of the drawings to refl ect the construction process and the phasing of

work. These are called general arrangement drawings. The subcontractors

and fabricators must also produce their own shop drawings to reflect accurate details of certain items, such as precast concrete units, steel connections,

wall details, piping runs, and the like.

The need for accurate and complete drawings extends to the shop drawings, as these are the most detailed representations and are used for actual

fabrication. If these drawings are inaccurate or incomplete, or if they are based

on drawings that already contain errors, inconsistencies, or omissions, then

expensive time-consuming confl icts will arise in the fi eld. The costs associated

with these confl icts can be significant.

1 This is based on two of the authors’ personal experience in working with the construction industry. This cost includes the expense of obtaining bid documents, performing quantity takeoff, coordinating with suppliers and subcontractors, and the cost estimating processes.

Inconsistency, inaccuracy, and uncertainty in design make it difficult to

fabricate materials offsite. As a result, most fabrication and construction must

take place onsite and only after exact conditions are established. Onsite construction work is more costly, more time-consuming, and prone to produce

errors that would not occur if the work were performed in a factory environment where costs are lower and quality control is better.

Often during the construction phase, numerous changes are made to the

design as a result of previously unknown errors and omissions, unanticipated

site conditions, changes in material availabilities, questions about the design,

new client requirements, and new technologies. These need to be resolved by

the project team. For each change, a procedure is required to determine the

cause, assign responsibility, evaluate time and cost implications, and address

how the issue will be resolved. This procedure, whether initiated in writing or

with the use of a Web-based tool, involves a Request for Information (RFI),

which must then be answered by the architect or other relevant party. Next a

Change Order (CO) is issued and all impacted parties are notifi ed about the

change, which is communicated together with needed changes in the drawings. These changes and resolutions frequently lead to legal disputes, added

costs, and delays. Web site products for managing these transactions do

help the project team stay on top of each change, but because they do not

address the source of the problem, they are of marginal benefit.

Problems also arise whenever a contractor bids below the estimated cost

in order to win the job. Contractors often abuse the change process to recoup

losses incurred from the original bid. This, of course, leads to more disputes

between the owner and project team.

In addition, the DBB process requires that the procurement of all materials be held until the owner approves the bid, which means that long lead time

items may extend the project schedule. For this and other reasons (described

below), the DBB approach often takes longer than the DB approach.

The fi nal phase is commissioning the building, which takes place after construction is fi nished. This involves testing the building systems (heating, cooling,

electrical, plumbing, fi re sprinklers, and so forth) to make sure they work properly. Depending on contract requirements, fi nal drawings are then produced to

reflect all as-built changes, and these are delivered to the owner along with all

manuals for installed equipment. At this point, the DBB process is completed.

Because all of the information provided to the owner is conveyed in 2D

(on paper or equivalent electronic fi les), the owner must put in a considerable

amount of effort to relay all relevant information to the facility management

team charged with maintaining and operating the building. The process is

time-consuming, prone to error, costly, and remains a significant barrier.

As a result of these problems, the DBB approach is probably not the

most expeditious or cost-efficient approach to design and construction. Other

approaches have been developed to address these problems.