Time Impact Analysis and Fragnets

Why Time Impact Analysis Matters on the CCM Exam
Time Management is one of the core domains of the CMAA Certified Construction Manager (CCM) examination, and within that domain, schedule delay analysis is among the most heavily tested technical skills. Time Impact Analysis (TIA) is the delay-analysis method most widely accepted by owners, contractors, courts, and boards of contract appeals, and it is the method explicitly favored in the CMAA Standards of Practice and in AACE International Recommended Practice 29R-03 (Forensic Schedule Analysis) and 52R-06 (Time Impact Analysis). A construction manager who cannot evaluate a contractor's request for a time extension, defend an owner against an unsupported delay claim, or quantify the schedule effect of an owner-directed change is not performing the full scope of the CM role. The exam therefore expects you to understand not just the definition of a TIA, but the mechanics of building and inserting a fragnet, the logic of float and critical path, the distinction between excusable, compensable, and concurrent delay, and the contractual timing requirements that govern when a TIA must be submitted.

What Is a Time Impact Analysis?
A Time Impact Analysis is a forward-looking (prospective) schedule analysis technique used to quantify the effect of a specific delay event or change on the project completion date. The analysis takes the most recent accepted schedule update that existed immediately before the delay event, inserts a small network of activities representing the delay or change (the fragnet), recalculates the critical path method (CPM) schedule, and compares the new projected completion date against the completion date shown before the insertion. The difference, if any, is the time impact attributable to that event.

Key characteristics of a TIA:
• It is event-specific: each delay or change is analyzed individually.
• It is prospective: it is ideally performed at the time the event occurs, before or while the impact is unfolding, rather than after the project is complete.
• It is contemporaneous: it uses the schedule update in effect at the time of the event, reflecting actual progress to date.
• It is additive: a chronological series of TIAs builds a complete picture of entitlement over the life of the project.
• It isolates the impact of a single party's action by holding everything else in the schedule constant.

What Is a Fragnet?
A fragnet (short for fragmentary network) is a small subnetwork of activities, durations, and logic relationships that models a change or delay event. Rather than modifying existing activity durations arbitrarily, the analyst creates discrete new activities that describe what actually must happen because of the event, then ties those activities into the existing schedule with predecessor and successor relationships.

A typical fragnet for an owner-issued design change might include:
• Issue RFI or notice of changed condition
• Owner/designer response or revised drawing issuance
• Pricing and change order negotiation
• Procurement of new or revised material
• Removal of installed work (if applicable)
• Installation of changed work
• Inspection and acceptance

Each activity is assigned a realistic duration, and the fragnet is logically tied to the activity it interrupts (predecessor) and the activity that cannot proceed until it is complete (successor). A well-built fragnet is the heart of a credible TIA; a poorly built one is the most common reason a TIA is rejected.

How a Time Impact Analysis Works: Step by Step
Step 1 – Identify the delay event. Define precisely what happened, when it began, who caused it, and what work it affected. Gather daily reports, RFIs, correspondence, meeting minutes, and photographs.

Step 2 – Select the baseline for analysis. Use the most recent accepted schedule update whose data date immediately precedes the delay event. This is sometimes called the unimpacted or pre-impact schedule. Do not use the original baseline if progress has occurred; using a stale schedule is a classic error because it ignores the contractor's actual status and float consumption.

Step 3 – Record the pre-impact completion date. Note the projected substantial completion date and the critical path before any changes are made.

Step 4 – Develop the fragnet. Build the activities, durations, and logic that represent the event. Durations should be supportable by actual records (for a retrospective TIA) or by reasonable estimates (for a prospective TIA).

Step 5 – Insert the fragnet. Tie the fragnet into the schedule at the correct logical point. Do not change any other activity durations, logic, constraints, or calendars.

Step 6 – Recalculate the schedule. Run the CPM calculation. Observe the new projected completion date and the new critical path.

Step 7 – Compare and quantify. Impact = (post-impact completion date) minus (pre-impact completion date). If the fragnet absorbs only available float and the completion date does not move, there is no time extension entitlement, even though the event may still have cost consequences.

Step 8 – Evaluate concurrency and responsibility. Determine whether a contractor-caused delay was driving the critical path at the same time. Concurrent delay typically yields excusable but non-compensable time (time extension, no delay damages to either party).

Step 9 – Document and submit. Prepare a narrative, before-and-after schedule printouts, the fragnet diagram, supporting records, and the requested time extension. Submit within the contract's notice and claim time limits.

Essential Related Concepts
Float ownership: Many contracts state that float is a shared resource that belongs to the project, not to either party, and is available on a first-come, first-served basis. A TIA that consumes float without extending completion generally does not support a time extension. Know your contract language.

Critical path: Only delays to the critical (longest) path extend the completion date. The TIA must demonstrate that the fragnet affected critical activities or created a new critical path.

Delay classification:
• Excusable and compensable – caused by the owner (e.g., design changes, late access, differing site conditions). Contractor receives time and money.
• Excusable and non-compensable – caused by neither party (e.g., unusually severe weather, force majeure) or concurrent. Contractor receives time only.
• Non-excusable – caused by the contractor. No time, and the owner may assess liquidated damages.

Prospective vs. retrospective TIA: A prospective TIA is performed when the event is identified, using estimated durations, and is the preferred approach because it allows real-time decision-making. A retrospective TIA (sometimes called a modeled, additive, multiple-base method under AACE 29R-03, MIP 3.7) is performed after the fact using actual durations. The exam favors the prospective, contemporaneous approach as the best practice.

Other delay analysis methods you may be asked to distinguish:
• As-Planned vs. As-Built – simple comparison of the baseline to actual; does not isolate individual causes.
• Impacted As-Planned – inserts delays into the original baseline, ignoring actual progress; widely criticized and often rejected.
• Collapsed As-Built (But-For) – removes a party's delays from the as-built schedule to show what would have happened; retrospective and subtractive.
• Windows / Contemporaneous Period Analysis – examines the critical path in successive time windows using schedule updates; observational rather than modeled.
• Time Impact Analysis – modeled, additive, uses contemporaneous updates, event-specific. Most credible for change-order time extensions.

Common Mistakes That Invalidate a TIA
• Using the original baseline instead of the current update.
• Changing logic, durations, or constraints unrelated to the event.
• Inflating fragnet durations without support.
• Ignoring concurrent contractor delay.
• Failing to meet contractual notice deadlines.
• Confusing a cost impact with a time impact.
• Claiming a time extension when the fragnet only consumed float.

Exam Tips: Answering Questions on Time Impact Analysis and Fragnets
Tip 1 – Anchor to the correct schedule. If a question asks which schedule should be used for a TIA, the answer is almost always the most recent accepted schedule update immediately preceding the delay event, not the original baseline and not the as-built schedule.

Tip 2 – Remember that TIA is prospective and additive. If answer choices describe a method that removes delays from an as-built schedule, that is Collapsed As-Built, not TIA. If a method inserts delays into the original unprogressed baseline, that is Impacted As-Planned, not TIA.

Tip 3 – Know what a fragnet is in one sentence. A fragnet is a fragmentary network of new activities with logic ties that models a change or delay event and is inserted into the schedule to measure its impact. Expect definition-style questions.

Tip 4 – Do the arithmetic carefully. Numeric questions will give a pre-impact completion date and a post-impact completion date, or will describe a fragnet duration and available float. Impact equals the shift in completion date, not the fragnet duration. Example: a 15-day fragnet inserted on an activity path with 10 days of total float yields a 5-day extension, not 15.

Tip 5 – Float consumption does not equal entitlement. If the completion date does not move, there is no time extension, regardless of how disruptive the event was. Watch for distractor answers granting time for float-only impacts.

Tip 6 – Classify the delay before choosing the remedy. Owner-caused and critical = time plus money. Neither party or concurrent = time only. Contractor-caused = no time, possible liquidated damages. Questions often embed the cause in the scenario and test whether you match it to the right remedy.

Tip 7 – The CM's role is to evaluate, not advocate. On a CMAA exam, the construction manager acts as an agent for the owner but is expected to apply the method fairly. Answers that have the CM reject a TIA without analysis, or approve one without verifying the fragnet, are wrong. The correct answer usually involves reviewing the fragnet logic, verifying the schedule update, confirming critical path impact, and checking for concurrency.

Tip 8 – Timing and notice matter. If a scenario mentions a contractor submitting a TIA months after the event with no prior notice, expect the question to test contractual notice requirements and the weakening of a retrospective claim.

Tip 9 – Only change what the event changes. Any answer choice that includes resequencing unrelated work, adjusting other durations, or removing constraints as part of the TIA insertion is describing an improper analysis.

Tip 10 – Recognize AACE terminology. If the exam references Recommended Practice 29R-03, Method Implementation Protocol 3.6 or 3.7 (modeled/additive methods), or RP 52R-06, these all point toward Time Impact Analysis.

Practice Scenario
A contractor's schedule update with a data date of June 1 shows substantial completion on December 15. On June 10 the owner issues a revised structural drawing requiring re-fabrication of steel connections. The contractor builds a fragnet with four activities totaling 20 working days and ties it as a predecessor to steel erection, which is on the critical path. After recalculation, the schedule shows completion on January 12. The contractor had no delays of its own during this period.

Question: What time extension is supported, and is it compensable?
Answer: The completion date moved from December 15 to January 12, so the supported extension is the number of days between those dates (approximately 20 working days, or 28 calendar days depending on the calendar used), not simply the 20-day fragnet duration. Because the event was owner-caused, affected the critical path, and there was no concurrent contractor delay, the delay is excusable and compensable. The CM should verify the fragnet durations, confirm the logic ties, and recommend a time extension with associated delay costs.

Quick Reference Summary
• TIA = insert fragnet into current update, recalculate, compare completion dates.
• Fragnet = small network of new activities modeling the event.
• Use the schedule update immediately before the event.
• Impact = shift in completion date, not fragnet length.
• Float consumed without a date shift = no time extension.
• Owner delay on critical path with no concurrency = time and money.
• Concurrent delay = time only.
• Contractor delay = no time.
• Change nothing except the inserted fragnet.
• Submit promptly within contract notice provisions.

Master these principles and you will be able to handle both conceptual and calculation-based questions on Time Impact Analysis and fragnets with confidence on the CCM exam.