LBMS is primarily a production management system. However, in some stages of most projects, production is not the bottleneck. Inspections or design changes can drive production. However, these are both somewhat impacted by how well production is run in the project and how good the plan is. For example, inspection failures are often a direct consequence of other problems described in my previous articles – working out-of-sequence or overcrowding locations causes details to be overlooked. The continuous pressure to start as soon as possible may result in starting before design has been completed and all decisions made.
Design issues and inspection failures lead to other problems which can easily start to cascade. In most cases locations cannot be completed. The natural reaction to this is to move to the next location and to start the next subcontractor in the problem location. Although this feels good because progress is being made, ultimately the project will get out of control. Working around issues without losing control is possible if there are a few issues and the project has many available locations. When design changes start impacting multiple locations and multiple trades, chaos is almost inevitable. [In claims literature, these cascading impacts of multiple changes are called “disruptions” of production. My first consulting assignment related to scheduling was to evaluate the impact of hundreds of change orders to the feasibility of a construction schedule in support of a claim. This is not easy after the fact. Adequate records should be kept during the process and the fact that the situation is getting out of control should be communicated early and aggressively.]
To mitigate the impact of inspection failures, I recommend convincing the inspectors to inspect by location. They should buy in to the location breakdown structure of the project early. Some inspectors stop when they find the first issue, requiring multiple inspections for each location. If possible, inspectors should be convinced to inspect the whole location and to record all issues. It is a good practice to ensure good quality by paying special attention to the first location. Implement internal inspections in a lot of detail in the first location. Have the subcontractor redo the work as many times as needed and allow him to continue to other locations only after all issues have been fixed in the first “model” location.
Inspections should be managed as production tasks. The scope of the task should include the actual inspection and any rework required to fix the issues and re-inspect. This will generate an inspection forecast which can be discussed with the Owner and with the subcontractors. It is a direct measure of the success of inspection process and the quality of the subcontractor. Because the rework is associated with inspection task, the original production task can be closed out in the location instead of “reserving” an arbitrary 5% for inspections.
Design issues may be harder to solve before they happen. Reviewing design and finding any constructability issues early is critical and work should not be allowed to start before the review has been done. It is also important to verify that the workers have access to the coordinated documents. Too often BIM coordination is carried out, clashes are resolved but the workers do not know anything about BIM and are using an uncoordinated set of drawings. I have even seen projects where drawings of different dates were used by different crews of the same subcontractor!
Caption: 2D drawings should be a standard deliverable from your coordination efforts. Composite drawings, such as the one above, are assembled to quickly and easily see the relationship between all systems after coordination is complete. Such composite drawings let site teams identify what other systems would be impacted if field changes are necessary. Composite sleeve drawings can also be produced and are a great tool for site teams (mainly superintendents) to quickly verify that all necessary penetrations have been laid out prior to a concrete pour.
If design changes happen, they should be incorporated into the schedule to evaluate their impact. Changing the Location Breakdown Structure may be useful to isolate the impacted areas. Additional tasks can be added as fragnets. It is a good practice to update the flow to go around impacted areas. However, when the flowline schedule starts to look confusing because of all the design change modifications the site is probably starting to feel confused as well and it is time to raise the red flag and have a frank discussion with the Owner.
Best sure you are caught up with all the articles in this series:
Part 1: Beyond Start Dates
Part 2: Get the Subs Involved
Part 3: Manpower and Suspensions
Part 4: Control Actions
Part 5: Planning the LBS
Part 6: Clarifying Scope
Part 7: Look-Ahead Plans
Part 8: Running Parallel Schedules
Part 9: Resource Graphs
Part 10: Production Rates and Location Sequence
Part 11: Using 5D with LBMS in Subcontractor Meetings
Part 12: Deliveries and Lay-Down Areas
Part 13: Starting As Early As Possible Will Hurt Your Project
Part 14: Buffers Are Important for Production Control
Part 15: Implement Control Actions as Soon as Possible
Part 16: In LBMS It Is Possible to Work Too Fast!
Part 17: Keep Chaos Out of the Construction Schedule
Part 18: Additional Types of Out-of-Sequence WorkPart 19: A Lot of Activity, But Little Progress