Master the Time Impact Analysis (TIA): A Step-by-Step Construction Delay Guide
The Time Impact Analysis (TIA)—also known as the Time Impacted Window Analysis—is widely considered the gold standard prospective methodology for analyzing delay claims in CPM (Critical Path Method) construction scheduling. Standardized by AACE International (Method Implementation Protocol 3.7 in RP 29R-03) and the Society of Construction Law (SCL), TIA calculates the specific time extension due to a delay event by modeling its impact on an updated schedule at the time the event occurs.
This guide breaks down the core mechanics of TIA and demonstrates a real-world project example step-by-step.
TIA Core Principles & Industry Standards
TIA is a prospective, prospective-contemporaneous, or prospective-modeled methodology. Unlike retrospective techniques like As-Built vs. As-Planned, TIA asks: “What was the projected impact of this specific delay event on the remaining project completion date at the time the event occurred?”
- Contemporaneous Baseline/Update: The analysis utilizes the approved schedule update immediately preceding the delay event (the “unimpacted schedule”).
- Sub-network (Fragnet): The delay event is modeled as a logical sub-network of activities (a “fragnet”) with realistic durations and logical relationships.
- Prospective Impact: The fragnet is inserted into the unimpacted schedule to measure the movement of the critical path and completion date.
5-Step TIA Preparation Guide
1.Select the Validated Unimpacted Schedule Update:Establish the clean baseline update.
Identify the approved Primavera P6 or MS Project schedule update whose Data Date immediately precedes the onset of the delay event. Verify that out-of-sequence progress, open ends, and incorrect constraints are resolved before proceeding.
2.Develop the Delay Fragnet:Define activities, durations, and logic.
Create a discrete sub-network representing the delay event. Include activities such as Employer/Engineer Directive, Site Instruction Receipt, Engineering/Redesign, Material Procurement, and Site Execution. Assign actual start dates and estimated durations backed by contemporaneous records (RFIs, letters, daily logs).
3.Run the Unimpacted Schedule Baseline:Capture pre-delay critical path.
Recalculate (schedule) the unimpacted schedule up to the delay Data Date without the fragnet. Document the pre-delay Critical Path, Total Float, and Contract Completion Date.
4.Insert the Fragnet & Recalculate:Create the Impacted Schedule.
Insert the fragnet into the unimpacted schedule update by tying pre-delay predecessor activities to the fragnet start, and connecting fragnet completion to logical successor activities. Recalculate the CPM network.
5.Measure Time Impact & Critical Path Shift:Quantify Excusable Extension of Time (EOT).
Compare the completion date of the Impacted Schedule against the Unimpacted Schedule. The difference represents the net quantifiable delay attributable to the specific event.
Practical Example: Commercial High-Rise Substructure Redesign
To illustrate how TIA functions in Primavera P6, consider a 30-story commercial tower project subject to an Owner-directed foundation redesign delay.
Scenario Baseline Context
- Contract Completion Date: December 15, 2026
- Unimpacted Schedule Update: Data Date = May 1, 2026
- Unimpacted Completion Date: December 15, 2026 (0 days float on Critical Path)
- Delay Event: On May 5, 2026, the Structural Engineer issues a Stop Work Order due to unforeseen soil conditions requiring deep pile foundation re-engineering.
Fragnet Activity Breakdown
| Activity ID | Activity Description | Original Duration | Predecessor | Successor |
| FRAG-100 | RFI & Engineer Stop Work Order | 5 Days | A1040 (Excavation Complete) | FRAG-110 |
| FRAG-110 | Structural Re-engineering & Revised Drawings | 20 Days | FRAG-100 | FRAG-120 |
| FRAG-120 | Engineer Approval & Material Mobilization | 10 Days | FRAG-110 | FRAG-130 |
| FRAG-130 | Execution of Additional Deep Piling | 15 Days | FRAG-120 | A1080 (Substructure Raft Pour) |
Impact Analysis Results
| Analysis Stage | Data Date | Substructure Raft Start | Projected Completion Date | Net Critical Delay |
| 1. Unimpacted Schedule | May 1, 2026 | May 10, 2026 | Dec 15, 2026 | Baseline (0 Days) |
| 2. Impacted Schedule (With Fragnet) | May 1, 2026 | June 29, 2026 | Jan 31, 2027 | 47 Calendar Days |
Conclusion: Inserting the 50-calendar-day fragnet into the critical path shifted activity A1080 (Substructure Raft Pour) by 50 days, pushing project completion past the contract deadline by 47 Calendar Days (accounting for calendar non-working days). The Contractor is entitled to a 47-day Extension of Time (EOT) and relief from liquidated damages.
Best Practices for Successful TIA Submittals
- Notice Compliance: Ensure the TIA is submitted within the contractually mandated timeframe (typically 14–28 days after the delay event onset).
- Isolate Events: Do not combine multiple unrelated delays into a single fragnet. Model each delay event independently to properly assign entitlement.
- Contemporaneous Proof: Attach RFIs, site logs, weather records, and formal correspondence directly as backup exhibits for fragnet durations.
