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In the traditional ‘design-bid-build’ approach, the owner warrants the correctness of the plans and specifications to the construction contractor. In the event of an error where the construction contractor incurs additional costs, that cost is met by the owner with little prospect of recovery from the designer. ‘Design-build’ eliminates this gap because the designer-builder has no one but himself to blame for defective plans, specifications or differing site conditions.
Where the designer designs the project around current-generation products, any proposed substitution of new or alternative products after bidding can require revisions to the structure and/or mechanical or electrical components to accommodate the new product. In such an event, the question arises as to who is going to pay for the resulting charges? ‘Design-build’ solves this problem; the ‘design-build’ entity selects the equipment and then designs the building around the selected equipment, which seems a more logical way to proceed.
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The traditional ‘design-bid-build’ method of contracting can suffer from under-optimisation when individual project participants seek to optimise their own positions – for example, the total cost to the owner of the steel frame of a building includes the cost of the engineering to determine the required steel sections plus the cost of the steel.
The designer has little incentive to achieve the minimum amount of structural steel, his concern being to spend only sufficient design time necessary to ensure there is enough steel to meet both gravity and seismic loads.
INCENTIVE
With ‘design-build’, the entity has an incentive to use the optimum amount of engineering in order to achieve the optimum amount of steel required for the structure. This is not to say that the ‘design-build’ results in unsafe structures; rather, it reduces unnecessary quantities of steel and concrete, etc. which do not necessarily add to the robustness of the structure.
‘Design-build’ may reduce the administrative burden on the owner because there is one award and one contract to administer. The total cost of the project becomes apparent earlier with ‘design-build’. In traditional ‘design-bid-build’ construction, costs are not known until bid opening, and it is possible to spend money on a design that the owner may not be able to build.
Frequently construction bids exceed the project budget, which results in the project having to be redesigned to bring it to within budget, thus delaying completion.
What is the risk? Under the traditional ‘design-bid-build’ contract arrangement, the owner has full control over the details of the plans and specifications, and does not publish them for bids until it is satisfied that they reflect the owner’s requirements. With ‘design-build’ the owner gives up some of this control.
Moreover, the owner must confirm its requirements much earlier. With traditional ‘design-bid-build’, if the owner is at all indecisive as to its requirements, it can clarify them during the design phase after it sees where the designer is heading. With ‘design-build’, such changes can be very expensive and disruptive, impacting on both costs and completion.
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FEATURED COMMENT
A good point regarding value engg. in DB but still it is not an easy procurement process to follow for public sector wor