Over the past decade, a great deal of development work has gone into BIM and how the 5D QS contributes to that process.
Out of all of this investment and research, the single most important element in relation to the 5D QS contribution to BIM is revisioning because it enables living cost planning - the ability to estimate something that is based on current design.
In Real Time
The biggest problem with creating and managing a bill of quantities (BoQ) or any form of quantities is that the day the quantities are finished they are out of date. For a BoQ, this could be by one to two months on average and sometimes a lot more.
This is because the design documents are frozen for a period to allow preparation of the quantities. In the case of a detailed set of quantities like a BoQ, it is not cost or time effective to redo the BoQ at regular intervals and on large projects; plans to remeasure the BoQ often fail because it is not possible to complete the task within a timeframe that is useful. Historically it has always been expected that a BoQ has a life equal to the project but the reality is that the BoQ was out of date the day it was released and it was never going to be accurate at any point in the build. Without revisioning, a BoQ’s main purpose is to provide a consistent tender at that point in time and not an accurate cost estimate that could be relied upon throughout.
This is no longer an acceptable parameter.
5D and BIM make it entirely possible to revision a model at any stage and across any element of a design – before (for cost planning, Quantity take off [QTO] and BoQ), during (for end cost forecasting and valuation of variations) and after completion (for maintenance and replacement cost estimating) if the cost data has been dynamically linked to the model information as part of the BIM Execution Plan.
The ability to revision something and make it current is happening now on a whole range of projects. This same technique is used not just for quantity takeoff but for living cost planning and to reconcile each cost plan or value variations or even value progress payments.
This one technique of revisioning benefits the entire downstream project team and is changing the role of the QS dramatically, which is bizarre when you consider that the most significant change (in the QS profession as a whole) that I have seen during my 32-year career was the industry-wide adoption of Excel.
Technology is the Enabler, 5D QS the Driver
Technology is the tool that supports the BIM and is available now. It is the 5D QS committed to the technology and how it benefits BIM that drives revisioning and what it can bring to a project at any stage.
CostX is one of the tools that revisions well and allows the 5D QS to look through a model and compare it to one that we had previously measured. It doesn’t matter whether we measured it yesterday or whether we measured it a year ago, we can still compare it.
Being able to recalculate something quickly, over and over and over again is a very powerful resource in saving the project time and money. It is however, still misunderstood across the industry because historically, quantities and estimates are only called for at the project sign-off times. It is something that is known to be done once, not over and over.
Upon compiling the quantities of a project through CostX, any form of quantification or estimate can be created quickly and reconciled via a report that describes each quantity change.
That one simple task can be applied the whole way through a project. This notion of “I want quantities I can rely upon” becomes very apparent and achievable. It’s the single point of change in a QS tool kit today.
In relation to CostX, mapping is king. Our industry talks a lot about the need for a standard classification system. CostX doesn’t rely on classifications.
All the parameters within an element in the design can be mapped almost like a Google search, “spidered” through the design. This allows us to query a model for the information that we need rather than having someone classify it for us and tell us where it should be. It puts the control in the hands of the user, allowing us to interrogate the model data and establish clear parameters for that data in preparation for design changes to come.
This also means that mapping of the model data can begin at any stage – it’s never too late, although there are significant benefits in applying mapping at the start of a project so that the data can build throughout the design stages. The design team can make decisions on current information at key points in the design development without compromising the integrity of the design.
Mapping effectively develops layers of information at each design change. Too much information at the beginning of the process and it would actually prohibit the design from developing. This is a technique that a 5D QS brings to the design team early on, knowing the key parameters in the data that will build the map most effectively and benefit everyone downstream.
Without revisioning, it’s just not 5D
Appointing a QS needs to move away from whether you need a 2D or 5D estimate; it is important to start thinking in terms of what information is needed at the current stage of the design and how it can help as the design develops. Ideally the 5D QS should be involved at concept design. Whilst not much information is needed within this stage, it provides the opportunity to set the master map and build the layers from there for fast and efficient revisioning at any time later in the design and build.
To be successful, projects must have a BIM Execution Plan which defines what the 5D QS requirements are. Designers need to model the way projects are built and bring all consultants into the design early. This is where decisions are made and efficiencies and cost savings are most likely identified and achieved. It’s important to work with people who know what they are doing and can demonstrate their value.
Early project team collaboration means fewer variations, delays and disruptions during the construction. The BIM Execution Plan delivers on collaboration and allows for the full power of revisioning downstream. It you’re not revisioning, you are missing the biggest opportunity that 5D brings to building leaner whilst maintaining design integrity and delivering the project’s vision intact.