Although being one of the first decisions to make on any planned project, choosing the correct delivery system is potentially one of the most over looked and undiscussed parts of any build. - At Cooper and Kelling we say "No more!".
With any luck after just a short read you'll be better informed as to what both the Design-Bid-Build and Design & Build models are, what to expect from each, and what each format brings to the table, in regards to both their advantages and their disadvantages.
Design - Bid - Build (D-B-B)
With Design - Bid - Build being the long standing and traditional approach to any building work, it is perhaps the format your general client is most familiar with, which no doubt goes some way towards explaining its prevalence within the construction industry.
This model of construction is broken down into 3 clearly defined and often ridged steps:
Design - During this phase a client will typically retain an architect or architectural design service to conduct everything from on site surveys, planning drawings, planning applications, detailed structural drawings and building regulations applications. For most building projects the architect will usually work closely with the owner to discover their needs and to develop a written programme documenting these needs before the conceptual and final drawings are produced.
Bid - Once the designs are complete it is back to the owner who is now responsible for offering the job out for tender. During this phase any client should expect multiple bids to be received which will need to be clarified and discussed. Some clients may still utilise their architect to review each of the bids and seek any clarification from the builders. During this stage of the project you could also expect revisions to the original plans based on feedback from those bidding.
Build - (I'm sure you get the idea with this one, but just in case:) Once the project has been awarded to a contractor the bid documents (technical specifications and detailed drawings) usually remain unchanged. Should design changes be necessary during construction, whether initiated by the contractor, owner, or as discovered by the architect, the architect may issue sketches or written clarifications to accommodate these. Hopefully though your project will continue through the build phase until it's completion.
Advantages of D-B-B
The client is in full control of both the design and the construction.
The design is completed prior to the project being awarded to a builder.
Accepting bids increases the level of competition and can drive the price down.
Construction costs are fixed once the contract has been awarded.
Disadvantages of D-B-B
Requires a certain amount of both expertise and resources from the client.
The responsibility for a successful build is shared.
The client is at risk to the builder for any design errors.
The design and build phases are sequential leading to a longer schedule.
Multiple contracts - multiple points of contact.
Design and Build (D-B)
With only 40% of all completed building projects in 2011 using the Design & Build format, it is still fairly new to the scene and this is no doubt due to the fact it can seem like a daunting option from the outset. However there is no real reason it needs to be!
Unlike the traditional D-B-B approach design & build projects tend to be a-lot more fluid with less rigidity in their steps.
Design - In the previous model we saw that during this stage it would usually be the clients responsibility to appoint an architect to begin the design aspects of the job. With D-B however a client will usually appoint a single firm who either hold an architect or architectural designer on staff. Subsequently during this phase you will notice an increased level of communication between the principle contractors and designers. Principle contractors wills often want to be very involved in the design from early on, discussing the design specification itself and working with the architect from the early stages aiming for the absolute best results. You should also expect your contractor to be able to produce their own schedule of works based upon this increase of communication with the principle designer which will run along side the design work to keep you informed of what to expect at each stage even before the work has begun. As with the D-B-B method you will still be provided with completed planning drawings, planning applications, detailed drawings and building regulations applications, but can also expect a lot less of the revisions encountered during the 'Bid' phase of the previous model.
Build - Whilst not being too different to the building phase within the previous model, D-B does have it's differences. Similarities, (although complete reversals) can be drawn from the Design phase of this method also. As with the above step you should see an increased level of communication between your principle designer and principle contractor at this stage. It would not be unusual to see your architect still taking an active role within the build itself either by inspecting what is going on or (as is the case with ourselves) managing the entire project through to completion. You should also expect fewer revisions and even fewer deviations from the original plans as a lot of this would have been eliminated during the design phase. As with the previous model all being well this phase should continue right through to completion.
Advantages of D-B
Requires less expertise and resources from the client.
Single entity responsible for both the design and the build.
Construction often begins before the end of the design phase allowing for a shorter schedule.
Larger emphasis on cost control.
Construction costs known and fixed during the design phase.
Disadvantages of D-B
Requires a comprehensive and carefully planned design specification.
Less control for the client between the design and build phases.
Less bids can lead to a potential higher cost.
The Brass Tacks
While a lot can be said for each of the above models and whilst you could not argue that either should be used on absolutely every job - the Design & Build tends to offer more to the modern client than the traditional Design - Bid - Build alternative. Generally speaking, across every aspect of your project you should not only notice the D-B method saving you time but money too! Not to mention the relief of being able to avoid most of the stress a building project can bring - leaving you to enjoy the design phase and watching your dreams come to fruition.
Fundamentally it is difficult to argue with the hard stats and statistics like those below which were released by the Construction Industry Institute:
Comparison of Project Delivery Methods: Design - Build VS. Design - Bid - Build
Unit Cost: 6.1% Lower
Construction Speed: 12% Faster
Delivery Speed: 33.5% Faster
Cost Growth: 5.2% Less
Schedule Growth: 11.4% Less