Example of the Critical Chain Method (CCM) for Building a Backyard Deck

The Critical Chain Method (CCM) is a project management technique that focuses on resource availability and constraints, rather than task dependencies, to determine the critical path of a project¹. The CCM aims to reduce project duration and avoid resource conflicts by using buffers and resource leveling strategies².

To use the CCM for building a backyard deck, you need to follow these steps:

• Step 1: List all the activities or tasks required to complete the project, such as measuring, cutting, assembling, painting, etc.
• Step 2: Estimate the duration of each activity or task, based on the resources available and the complexity of the work. Use realistic estimates without adding any safety or buffer time.
• Step 3: Identify the resources needed for each activity or task, such as people, materials, equipment, etc. Consider the availability and capacity of each resource and how they are shared among different tasks or projects.
• Step 4: Draw a network diagram that shows the sequence and dependencies of the activities or tasks, using nodes to represent activities and arrows to represent dependencies. Use resource leveling techniques to avoid overloading or underutilizing any resource. Depending on the availability of resources, this may involve shifting some tasks to start later or finish earlier.
• Step 5: Identify the critical chain, the longest path in the network diagram that considers both task dependencies and resource constraints. The critical chain determines the minimum completion time of the project and any delay in any activity on this path will delay the entire project.
• Step 6: Add buffers to protect the critical chain from uncertainties and variations. There are three types of buffers in CCM: project buffer, feeding buffer, and resource buffer.
  • Project buffer: This is a time cushion added at the end of the critical chain to protect the project completion date from any delays or risks along the critical chain. The size of the project buffer is usually calculated as a percentage of the total duration of the critical chain (e.g., 25%).
  • Feeding buffer: This is a time cushion added at each point where a non-critical chain (or a feeding chain) merges with the critical chain. The purpose of the feeding buffer is to prevent any delays in the non-critical chains from affecting the critical chain. The size of the feeding buffer is usually calculated as a percentage of the total duration of the feeding chain (e.g., 50%).
  • Resource buffer: This is a time cushion added before each activity on the critical chain that requires a scarce or critical resource. The purpose of the resource buffer is to ensure that the resource is available and ready when needed for critical activity. The resource buffer’s size depends on the resource’s availability and demand.

Here is an example of using the CCM for building a backyard deck:

The critical chain for this example is A-B-D-F-G-H, with a minimum completion time of 20 hours without buffers. Any delay in any of these activities will delay the entire project. The activities C and E are not on the critical chain and have some flexibility in their scheduling.

The project buffer is added at the end of the critical chain and has a size of 25% of 20 hours, which is 5 hours. The feeding buffer is added at point D where activity E merges with the critical chain and has a size of 50% of 2 hours, which is 1 hour. The resource buffers are added before activities B, C, D, E, F, G, and H because they all require either a carpenter or saw or both, which are scarce resources. The size of each resource buffer depends on how much time it takes to secure or release these resources.

The total project duration with buffers is 26 hours. The project manager can monitor the consumption of the buffers and take corrective actions if needed to keep the project on track.