LBMS is a better way to coordinate specialist subcontractors and to achieve a harmonious workflow with minimum interference. Because production is not a black box self-managed by subcontractors in the LBMS world, a shared understanding becomes critical for project success. The previous posts in this series focused on data collection and resource discussions. This post centers on production rates and logic.
In traditional contracts, subcontracts are given a total duration and sometimes intermediate milestones. Subcontracts refer to CPM schedule durations. However, production management is undertaken by the subs and they have a lot of freedom on how to implement the master schedule objectives. The original CPM dates do not tend to hold because the CPM schedules have no buffers, so it is easy for any subcontractor to claim delays and basically invalidate the original commitment. LBMS takes a more active role in management. Everyone needs to follow the same location breakdown structure (LBS). Location sequences are synchronized. Production rate targets are set based on quantities and assumed crew size. And in order to make this work in practice, everyone needs to understand the plan and the consequences of not achieving the plan.
LBMS control focuses on production rates. Optimally, production rate targets are set in the contract or even in the RFP document. In any case, the contracts should include a clause about control action requirements if the planned production rate is not being achieved. Subcontractors should understand both the numerical production rate target (no. of units/day) and how that translates into durations to finish each location (days/location). The goal is to achieve a consistent pace with continuous flow. The same crew should continue on the project from the beginning to the end of the subcontractor’s performance. The subcontractor’s responsibility is to staff the project appropriately to achieve the production rate target and maintain the staffing level to produce a similar amount of work week after week.
Caption: during a Lean Construction pull planning session, subs commit to crews and production rates understanding that the GC is committing to free and clear work locations in order to avoid stops and starts
In addition to the production rate, location sequences are critical. Instead of doing the “easy” work first, a certain sequence has to be followed. All work needs to be finished in a location before moving on to the next location. The typical behavior of subs has been to cherry pick work based on a schedule of values and finish locations partially. Location sequences have tended to be flexible based more on location availability than a predetermined plan. This behavior should not happen on an LBMS project because everything is closely synchronized together – if one sub works out of sequence the next sub must do so, too. Location sequences can be best enforced by tying payments to location completion (instead of percentage completed). Out-of-sequence work should not be invoiced at all. Logistics can be organized so that materials can be delivered only in location sequence (because it is difficult to work out of sequence if materials are not available!). And finally, subcontractor meetings should include a review of control charts concentrating on any delayed and suspended locations. Peer pressure often works well here…
Working with Subs requires good organizational and social skills. And combining the social characteristics of Lean Construction’s Last Planner and the analytical characteristics of LBMS just makes sense. Here are two resources to help you learn more about this approach:
Finally, catch up with the other articles from this series: