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Create Thorough Task Plans to Avoid Firefighting on the Jobsite

Just controlling production rates is not enough even in an LBMS project. Other Lean techniques such as removing constraints are critical. As a best practice, maintain a checklist of prerequisites and constraints by task and by location for your LBMS project.  After all, the responsibility of production management is to look ahead and prepare tasks and locations for efficient work. Any ongoing operation can be reviewed based on production rates. And make it standard practice to get work ready a bit ahead of production.

 

Look-ahead planning is often done based on look-ahead time window such as six weeks. I have always preferred the approach of “task planning” where each operation is planned in detail in one document. A task plan includes schedule milestones, cost, quality requirements, an inspection plan, and a list of prerequisites that need to be completed for each location. Some of the prerequisites are unique and non-location-based such as making sure that the right size crew shows up. Others need to be reviewed for each location – for example, reviewing drawings for completeness, closing out any RFIs, making sure materials are available, cleaning up the location, or making sure that predecessor has left the location before starting work. The task plan creates a checklist that the production management can follow for each location.

 

superintendent task planning checklist 

Caption: Be as thorough as possible with the task plan, including assigning a resource responsible for that task.  Be sure to list all the steps necessary to complete a task so that no details are missed which might cause a delay later on.

 

It is typical that constraints show up when work is already being installed. For example, the preceding trade did not complete all their scope or no one reviewed the drawings and there were omissions or the subcontractor ran out of material. These issues cause low production rates (unrelated to actual productivity of the crew), inability to complete locations, failing inspections, poor quality work, rework, and problems for the succeeding subcontractors. It is much better to prevent these problems than fight the fires when they do happen.

 

To mitigate these problems, prerequisite checklists should be in use for any work starting in the near future (by task, by location). Each prerequisite should have a responsible person. The status of action items should be reviewed weekly in subcontractor meetings. And action items should be completed before production is forecasted to enter the location. Optimal productivity can be achieved when 100% of constraints are cleared before starting in a location. This is what LBMS sets out to achieve. When everyone is able to work with optimal productivity, the remaining management concerns production rates to prevent schedule clashes.

 

Be 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 Work

Part 19: A Lot of Activity, But Little Progress

Part 20: How to Handle Inspections and Design Changes

Part 21: Preventing the Blow Fly Effect on the Jobsite

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Prevent the “Blow Fly” Effect on the Construction Jobsite

I have observed several times that subcontractors have resources on site even though there is no productive work for them. The crews (or rather the individual workers) can do a bit of work here and a bit of work there. But much of the time is spent looking for work or waiting for instructions. In our book, Location-Based Management for Construction (Kenley & Seppänen 2009) we called this the “blow fly effect” (workers buzzing around looking for work).  Naturally, this is very expensive for the subcontractor.  So I have started asking the question of why are they still there. Wouldn’t it be more economical to leave and return when more work was available?  The answer is yes from subcontractor perspective - if they have more productive alternative resources.  From the General Contractor’s perspective, the sensible answer depends on circumstances, but the most common answer is that the resources need to stay on site.

 

blowfly effect in construction 

Caption: Like flies buzzing around the back porch, construction workers are often found milling around the jobsite looking for any work they can pick up. But which is better: to let them demobilize and risk a timely return or keep them occupied with other tasks?  One best practice is to plan a work backlog for each trade – work in non-critical locations like a parking garage.

 

Letting the resources leave increases the schedule risk of the project per basic LBMS theory (please see video #3 – the difference between paced and asap tasks in the Schedule Planner video training series).  It may not be possible to get the resources back in a timely manner when work does become available or different workers may show up with their own starting difficulties.  In any case, momentum is lost on the project.  In terms of short disturbances of workflow it probably makes sense to have the workers wait and do small unproductive work.

 

IF the duration of work stoppage is long, it makes sense to demobilize.  Having resources on site who have nothing productive to work on is a drain on management capacity.  Superintendents do not let the workers stay idle. They are actively looking for work.  This diverts their energy from solving the actual root problem. Productivity claims are also a real risk. Keeping the resources on site adds cost and productivity claim risks. It also causes a lot of issues with starting too many locations at the same time, overlapping work in locations, etc., which in turn decrease the productivity of other subcontractors and may cause the site to become chaotic – not controlled by any plan (see Keep Chaos Out of the Construction Schedule for a discussion of out-of-sequence and out-of-logic work and When Activity on the Construction Site Can Mask Productivity Issues for a discussion of scope confusion and productivity loss when subcontractors are in the same location).

 

A better solution is to plan work backlog for each trade.  Work backlog can be tasks of small importance; for example, tasks with a lot of float and no real dependencies which can be done flexibly when required.  Work backlog can also be non-critical locations. For example, a parking garage is often not on critical path and workers can be diverted there when they run out of work in critical areas.  Best projects establish these work backlogs explicitly and only use them to balance times of low utilization.  If work on critical production tasks is continuous (good production control!), these work backlog tasks are done after finishing all work on critical tasks.

 

Be 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 Work

Part 19: A Lot of Activity, But Little Progress

Part 20: How to Handle Inspections and Design Changes

 

 

 

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How to Handle Inspections and Design Changes in the Construction Schedule

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!

 

trimble coordinated 2D composite drawings for subcontractors on construction jobsite

 

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 Work

Part 19: A Lot of Activity, But Little Progress

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When Activity on the Construction Site Can Mask Productivity Issues

A lot of activity, but little progress…

 

We recently visited a large hospital construction project which utilized LBMS and traditional CPM in parallel for production control. Their goal is to compare the two approaches. We call the upper floors of the project “LBMS floors” and the lower floors “ASAP floors.” The lower floors have started months earlier than the upper floors, but the progress is much slower. During a site walk, you can see a lot of activity on the lower floors. Many subcontractors are working on these floors with large crews. There are a lot of materials stored to supply all these subcontractors. It looks like progress is being made because there is a lot of activity. Anywhere you walk you can see someone working. In contrast, LBMS floors have one subcontractor working in each location. Materials are stored only for that subcontractor on each floor. The floors look practically empty and it feels like progress must be slow. Everyone is working at a more relaxed pace. However, production control data reveals that progress and productivity on these upper, more relaxed floors is much better than progress on the busy lower floors.

 

I argue that most US construction projects follow the management methodology of the lower floors of this project. Too many subcontractors are working in parallel in the same location. This creates an illusion of getting things done, but in fact causes everything to take much longer. Subcontractors may not always physically interfere with each other but the requirement for materials and the general confusion about what scope is finished by the preceding sub causes productivity loss. The same subcontractors perform better on similar scope in areas where only one subcontractor owns the space. I have earlier found this effect to be 30% or more and we are in the process of quantifying the difference in this project.

 

congested construction site3 

Caption: A particular location can look very busy; but that busy-ness might be masking scope issues, material congestion, or general confusion.

 

As we all know, CPM schedule reporting benefits from early starts. In contrast, LBMS penalizes early starts if the production rates do not match what has been planned. Focus controlling on production rates, not start dates, and measure subcontractors and superintendents on production rate performance!

 

Be 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 Work

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Additional Types of Out-of-Sequence Work on the Construction Jobsite

There are three special cases of out-of-sequence or out-of-logic work that are of distinct importance in LBMS projects. Subcontractors working in multiple locations at the same time instead of working in sequence cause issues with forecasting. Finishing 95% of a location and then moving to the next location is also typical. The third important issue is starting too many subcontractors at the same time in the same location.

 

Working in multiple locations at the same time instead of focusing resources on fewer locations results in locations taking longer to release to the next trade. Figure 1 at the bottom of this article shows this behavior with number 1. This requires either larger buffers or overlapping work with a successor trade which, in turn, leads to slowdowns. The reason of this behavior is that typically crew sizes are not considered in CPM and additional resources are always assumed to work in a separate crew that works in a different activity. The default action of subcontractors when required to add more people is to open up new locations. It requires training and active management to focus resources to finish work in one location only.

 

Current production control methods such as CPM pay more attention to starting than finishing. Locations often progress to 90% or 95% completion and then get suspended. If the successor tasks can start, the issue falls quickly out of production management’s radar. These small amounts of work in each location for each trade result in a large amount of manhours required in the end of the project to finish all partially finished locations. This contributes to the end of project rush. Suspended locations also make forecasting difficult. It is hard to know what the subcontractor is going to do next with all the open, partially finished work. Figure 1 at the bottom of this article shows this behavior with number 2.

 

To solve this issue we have had success with having subcontractors explain any suspended locations and committing to a continuation date. A more complete solution can be achieved if payment structures can be changed to be by location instead of paying for percentage completed.

 

Finally, letting too many subcontractors work in parallel in the same location causes a lot of inefficiency and slowdowns. In general, if the locations are small enough, two tasks with large space or lay-down area requirements should not be ongoing in the same area, even if they are not technically dependent. It has been empirically shown that overlapping work can result in 30%+ productivity decreases (for both the predecessor and the successor). This basically negates the benefit of starting the successor early because both the predecessor and the successor will take longer than needed. It is better to wait for a completely free location and then work faster. Figure 1 below shows this behavior with number 3.

 

3 examples of out of sequence work ramifications on construction schedule 

Figure 1: Example showing overlapping work (1) uncompleted locations (2) and overlapping work causing slowdowns (3).

 

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

 

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Keep Chaos Out of the Construction Schedule: Out-of-Sequence and Out-of-Logic Work Creates Unpredictability

Out-of-logic work means starting tasks in the same location in a sequence which breaks planned logic links. For example, if the plan had overhead MEP before installing studs, any studwork before overhead MEP would be out-of-logic work. Out-of-sequence work is starting locations of the same task in different sequence than planned. For example instead of starting on the 1st floor as planned, studwork starts on the second floor. Both of these are dangerous and can lead to chaos on a project. The main problem is the unpredictability – where will the subcontractors go next? Instead of work following the plan, the plan needs to keep up with the work.

 

Out-of-logic work rarely happens in the structural phase of the project. However, it is very common in interior work where dependencies are mainly “soft" and work can happen in many alternative sequences. Superintendents and subcontractors are actively looking for opportunities to start work. The logic in the schedule may be irrelevant to them or they may not understand the benefit of following a planned sequence. This causes difficulty with forecasts because they follow planned logic. If the logic change makes sense, there is no problem because it can be easily updated to detail tasks of the schedule. However, it is very common that random out-of-logic work happens on projects which basically invalidates any schedule optimization and in many cases causes productivity loss.

 

Out-of-logic work can be fixed easily by involving the subcontractors in pull planning meetings and committing to the collaboratively planned sequence (figure 1 shows a picture of a pull planning meeting). Any out-of-logic work should be immediately discussed. If there is a valid reason, the plan should be updated. Otherwise out-of-logic work should be stopped before the project gets out of control.

 

pull planning sessions with subs 

Best Practice: Utilize pull planning sessions with Subs.  What we have found is that GCs know the trades they self-perform and have copious amounts of data that can be harnessed and re-purposed. However, when it comes to subcontractor data, they are woefully lacking, simply because they have not asked. But part of the benefit of our approach is the very collaborative nature of working in concert with subs in pull planning sessions. By asking the subs for crew productivity rates, we can derive a schedule and optimize it to eliminate the stops and starts which hamper and frustrate subs' progress. This simple change can have a tremendous impact: subs are able to work more efficiently without the hassle of de- and re-mobilization.

 

Out-of-sequence work means that crews are flowing through the building in a different sequence than planned. It happens often because of open RFIs or design issues in a location or because deliveries have been done in wrong sequence. Sometimes out-of-sequence work happens because of subcontractor preferences – get the easy locations first to improve cash flow. The problem is that other succeeding contractors need to follow the same sequence and they may not know it in advance.

 

Delays can often result because a subcontractor ordered materials and prefabricated based on the planned sequence and the predecessor implemented an unplanned sequence change. If out-of-sequence work happens a lot, total chaos will result. The plan loses all value and it is impossible to predict what will happen next. Out-of-sequence work should only be allowed if there is a valid reason (inability to work in the planned location). In those cases it makes sense to resequence the plan completely. If there is no valid reason, subcontractors should be forced to follow sequence. Again pull scheduling meetings help because subcontractors agree to the sequence together.

 

To control sequence and logic everyone should commit to the plan, understand tasks and their dependencies and understand what the location-breakdown structure is. Visual Management tools such as production control wall (figure 2) will make this information easily accessible and improve the results on your project.

 

production wall concrete pours mep inserts 

Best Practice: Create one area in the trailer (we call it a Production Wall) where all crews can see their tasks and locations.  This way, there is never a question of who should be where, doing what, when, and why.

 

Be 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!

 

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In LBMS It Is Possible to Work Too Fast!

One of the fundamental differences between CPM and LBMS scheduling methods is related to durations. In CPM, shorter durations are always better. In LBMS, the production rates are synchronized so that durations are as balanced as possible between the trades. This enables continuous flow of production without delays in start dates. Implementing this in practice is challenging because if a subcontractor shows up with too large a crew and achieves better than planned production rate, it is very rare that the superintendent would agree to slow the subcontractor down. Proposals to increase production rate have a far higher degree of acceptance than any recommendations to decrease the production rate.

 

Too fast tasks are problematic in several ways. First of all, the project will only benefit from a fast production rate if every other subcontractor can speed up to match. This is unlikely because these preplanned production rates have been used by the subcontractors in scheduling their shop drawings, deliveries, and crew sizes. It may be easy for some subcontractors to increase production, but in most cases it is difficult to do this with every subcontractor. Therefore, any opportunities to increase production rates should be incorporated into the original schedule and faster work should be discouraged if it results in schedule conflicts with others.

 

Too fast subcontractors clash with their predecessors. They will run out of work and have to leave the project. Sometimes they try to work in parallel with their predecessor and both parties slow down as a result. This causes friction, poor productivity, and increased risk of cascading delays. If the crew leaves the site, it is difficult to get them back exactly when needed because the subcontractor allocates the crew to another project. Typically this causes return delays of one to three weeks which negate any benefits of faster work. The crew that returns may be different from the original crew with new start-up difficulties and a new learning curve. The problem is bigger with heavily-specialized crews which work only on a few tasks in the project; for example, an acoustical ceiling or casework contractor. In contrast, MEP contractors do not suffer as much from this problem because they have various tasks in the building where they can work when they run out of work in one task.

 

Buffers and workable backlog help to solve this problem. Buffers enable overly fast work to be detected before the subcontractor runs out of work. The subcontractor can be requested to slow down by decreasing crew size or by adding additional scope in each location. Alternatively, a work backlog of less critical activities can be developed to provide work continuity. Examples of good work backlog locations are mechanical rooms (when not on critical path), electrical rooms, and large open areas such as garages. Any task which does not interfere with other tasks (i.e. low material requirements, low space requirements) can be a work backlog task. If a work backlog location or task can be identified for a subcontractor, overly fast work is less of a problem as long as the subcontractor is not permitted to enter the same location as the preceding trade. If a work backlog cannot be identified for the subcontractor, work should be slowed down.

 

superintendents must control crew productivity rates to balance the project

Caption: It might be counter-intuitive for a superintendent to ask a crew to slow down, but balancing the productivity rates for the subs across locations is actually best for the project.

 

Read about a specific case of a sub working too fast in my colleague's article, Construction Superintendents Just Get Vico Production Control.

 

To learn more about the differences between CPM and LBMS, please download this whitepaper prepared for the American College of Construction Lawyers 2012 annual meeting. The paper compares and contrasts the traditional critical path method of construction planning with location-based scheduling principles.

Whitepaper: A Comparison of Traditional CPM and Location-Based Scheduling

 

Be sure to catch up with the other best practice 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

 

 

 

 

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Implement Control Actions as Soon as Possible

LBMS controlling theory focuses on preventing production alarms from becoming production problems on site. Buffers allow some time for control actions to take effect before a problem happens. In reality the lag times to implement control actions to alarms are unacceptably long. In the US, we have observed on large construction projects that it can take four weeks to implement a control action in response to an alarm. In Finland, the lag has also been unacceptably long at around 2-3 weeks.

 

Why does it take so long? In many cases it is because the parallel CPM schedule is showing that the activity is not on the critical path or is not delayed from schedule yet. However, LBMS works on production trends. A delay will happen in the future if something is not done now. Industry, which has for a long time been focused on firefighting, is not used to reacting to future delays if there are none at the present. However, for LBMS to create optimum results, actions should be taken immediately. Data collection, validation, discussions, and action should all happen in the same week.

 

Control actions take time before they are effective. For example, if the control action is to add resources to an undermanned crew, it is unlikely that all the required resources would show up on the next day. It often takes some time because those people are working on other projects and the subcontractor needs to finish work elsewhere to free up the resources. It often takes a few weeks to mobilize resources. If the lag to DECIDE on a control action is four weeks and the time required to fully implement is two weeks, six weeks have been lost on the project.

 

A good way to implement faster actions is to implement a Control Action Log as a project deliverable. The Control Action Log reports any production rate deviations and actions and includes:

  • Date found
  • Explanation of issue
  • Date control action made (or decision to not do anything)
  • Control action description (or why control action was not made)
  • Impact

 

This report makes it easy to calculate lead times from production alarm to control action. In some projects it has been added as an Owner deliverable to monthly reports and reviewed with the Owner weekly to show that action is being taken to address any production issues. A sample from a control action log is shown below:

 

control action log from commerical construction project

 

 

Effective production control can decrease project durations by 10% or more and increase subcontractor productivity. It certainly decreases the risk in the project. If you are an Owner or an Executive in a construction company would you not want to see any production problems addressed in real time to get these benefits?

 

See the Control Action Log and three other reports every Owner should have and how to produce them in the Production Controller video training series.

 

Also, be sure to catch up with the other best practice 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

 

 

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Buffers Are Important for Production Control

Buffers are a novel concept in LBMS. They function similarly to CPM lags during planning but they can be absorbed and are similar to float in controlling and forecasting phase. Buffers give superintendents time to react if there is a problem with predecessor’s production. They also make the project easier to control because there are fewer operations ongoing on site, they are of long duration and continuous and start dates are spaced out. Subcontractors work faster if there is work ahead of them so any time lost will be regained during production. That is the theory and there is evidence that it works (both empirical and simulation, for example try my production control game) but why are buffers not being used in LBMS schedules?

 

The main reason seems to be unfamiliarity with the concept. On the surface it seems that buffers delay the project and that is indeed the case during planning phase. However, in LBMS schedule optimization crews are added to balance flows and sequences are optimized. This typically results in a 10-20% compression in project schedule compared to the CPM start point. Durations in each location are typically shorter. This is fine because the subcontractors can work faster if they have the space and all constraints have been removed. Buffers are required to make sure that the subcontractors have the location available when they get there. Instead of delaying the project, buffers take it back closer to the original duration. For example, if LBMS is used to compress 20% of project duration based on continuous flow and subcontractor productivity data, buffers can then be added back to end with just a 10% shorter schedule.

 

adding buffers after tasks

Caption: One best practice is to place buffers between trades which cannot overlap; this example illustrates adding buffers between drywall, pipework, ceilings, and finishes.

 

Where should buffers be planned? Between any two trades which would interfere with each other when working in the same location or when the predecessor must be completed before the successor can start. Typically it makes sense to buffer tasks which are continuous, have high man-hours or require large lay-down areas. Important inspections should always be buffered. The buffer should be added AFTER the inspection to prevent delay caused by failed inspection. Buffers are not required for tasks which do not take a lot of space and can easily happen concurrently with other work (e.g. door installation).

 

apply buffers after important inspections 

Caption: Another best practice is to apply a buffer after important inspections. This way the buffer protects the schedule against a delay for the rework.

 

To make buffers easier to use, it makes sense to create a report of all buffered tasks. A new task should be started when the predecessor has been completed in the location and the buffer time has elapsed. This may lead to slight delays in the first location but if the work continuity is preserved and the task is of long duration, it is easy to catch up during production by just increasing the crew size by a few people.

 

To learn more about Location-Based Management System and how it is deployed in Vico Office Schedule Planner and Production Controller, please see:

Video Training Series: Schedule Planner

Video Training Series: Production Controller

 

And be sure to catch up with the other best practice 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

 

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Starting As Early As Possible Will Hurt Your Project

For some reason, controlling schedules has traditionally focused on controlling start dates instead of controlling the rate of production. As a scheduling tool, CPM promotes this behavior. You will always be better off in the CPM world if you start tasks as soon as possible. I have seen several CPM schedules which were completely misleading because work had started on all the floors at once. The schedule update was showing an early finish. In reality, the same crew was working on small part of the scope of each activity on each floor. CPM used the original planned durations and the series of activities on ten floors which were planned to be sequential and take five days (total of fifty days), were suddenly going to be all finished in five days. This is an extreme example but illustrates how CPM reporting rewards early start even if it does not actually bring any benefits to the project.

 

In Location-Based Management, start dates are delayed until the crew can work continuously (for tasks which have been decided to be continuous). This maximizes crew productivity. Start dates are also delayed by buffers. It is a good practice in planning to leave a few days or a week of time between two continuous tasks so that delays impacting predecessor do not automatically cause a cascading delay to all the successors. In a schedule without buffers any problem of the predecessor causes a problem to the successor making the project very difficult to control and causing a lot of firefighting and anxiety in projects. While this is easy to plan in theory, it is very difficult to implement during actual production.

 

Superintendents are not used to making mobilization decisions on the basis of long-term productivity of each operation. Their planning horizon tends to be a few weeks. The focus is on finding locations where work can start and figuring out what can be done NOW to improve progress on site. This also seems to be the natural way to make decisions. I have designed a production control game which all Vico Production Controlling training attendees can play. The game is based on a simple six story building with just a few tasks but realistic situations. Almost all the players remember to add buffers and plan for continuous flow. However, almost all of them “push control” the subcontractors and force them to start according to the schedule even if previous tasks are delayed. Both in reality and in the game they get penalized with slower production, location congestion, too many trades active at the same time, and slow starts by subcontractors.

 

vico production control game 

Caption: The Production Control Game is a virtual workshop for your team to learn schedule optimization techniques and their consequences in a simulation.  Played over email, participants react to turns of events at the virtual jobsite.  The goal, of course, is to respond to various disruptions and challenges by enacting control actions.  The best score is determined by the actual finish date, subcontractor manhours, and number of control actions taken.  During the game summary conducted over GoToMeeting, the team finds out what other players did differently and how that affected their scores. The best control actions win the day - and the game!

 

Early starts have limited or no benefit when the work cannot be carried out continuously. It is only possible to control the production of tasks with long, continuous production runs. Any control action will take time to implement – you need to discuss with the subs, they need to mobilize additional resources, and so on. If you are focusing on 5-day activities instead of a 50-day continuous task your only option is to focus on starts because you are unable to control production rates. This is one of the most important fact of life which causes projects to face continuous firefighting today. It is better to wait before starting the next trade and fix the production problems of the predecessor. You will be able to make better time with this approach – focus on the problem task, not the successor tasks.

 

When is the right time to start the next task in its first location? All the constraints should have been satisfied. The design related to the first few locations should be available, all RFIs answered, materials ready to be delivered, and equipment available. Predecessors should have completed in the location and cleaned up the location. When all of this has been completed, wait until the predecessor has advanced far enough ahead of the successor. The best way to see this visually is to calculate the number of free locations by looking at the vertical distance between forecast lines. Then it is time to start and with enough work ahead of the subcontractor you will be able to convince them to work fast without being afraid of running out of work.

 

The figure below shows the status of week 6 of one player in the production control game (note: each group will have different actuals so your game will most likely be completely different). The player made the choice to start Studs on week 7 even though Overhead MEP was not completed. If the production rate of studs is as high as planned this would not make any sense because they would run out of work almost immediately. In any case it would not make sense to start before locations 1 and 2 are finished. This would leave two locations as “space buffer” and give enough time to decrease crew size before conflict if production rate was too high. Figure 2 shows what happened by starting too early – slow down of both MEP and Studs contractor. Starting early can result in finishing late…

 

Fig 1 Production Control Game 

Figure 1: The player made the decision to start the following week. Based on forecasts start date should have been delayed by at least 1.5 more weeks.

 

Fig 2 Production Control Game

Figure 2: Too early a start resulted in loss of productivity, a few production alarms, and slowdown of the predecessor

 

Would you like your team to learn more about Production Control with this on-site game?  Just let me know!

 

And be sure to catch up with the other best practice 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

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