Place 20% time buffers around your constraint step…
Add 20% time buffers around constraint activities that fail or degrade most frequently under pressure, rather than distributing slack evenly across all workflow steps.
When This Fires
- Scheduling workflow that includes known bottleneck steps
- Planning sprints or project timelines where one step has high failure/delay risk
- After a constraint step failed or degraded because it ran out of time
- Any planning context where you're deciding how to allocate slack time
Common Failure Mode
Distributing buffer evenly because it feels "fair." Every step gets 20% extra time, which means the constraint gets the same protection as trivial steps. Under pressure, the constraint still fails while trivial steps have unused slack. Fairness is the wrong principle for buffer allocation — system throughput is. Protect the constraint; other steps can absorb their own variability.
The Protocol
(1) Identify your current constraint step (the one that limits overall throughput). (2) Add a 20% time buffer before the constraint (ensures input is ready). (3) Add a 20% time buffer after the constraint (absorbs output variability). (4) Reduce or eliminate buffers on non-constraint steps that rarely fail. (5) Track: does the constraint still fail under pressure? If yes, increase buffer. If the buffer is consistently unused, it's too large — reallocate some to other emerging constraints.