Positive and Negative Lag

Lag is the delay (positive) or advancement (negative) between dependent activities. An example of this would be waiting two days after pouring concrete before starting finishing work.

How positive/negative lag can affect the schedule:

• Excessive lag can compress the schedule artificially or push critical tasks out, skewing the critical path.
• Negative lag may create unrealistic overlaps between activities, leading to resource conflicts or schedule risk.
• Misused lag makes it difficult to accurately model project progress.

Best Practices:

• Apply lag only when it reflects real-world constraints or necessary sequencing.
• Avoid “padding” lag to adjust schedules artificially.
• Regularly audit lag values during schedule updates to ensure they remain realistic.