Impacted As-Planned vs. Time Impact Analysis, Same Project

The Two Methods, in Brief

Impacted As-Planned (IAP) takes the project’s original, unprogressed baseline network, inserts a fragnet representing the disputed delay event directly into that pristine logic, and recalculates. It’s quick and cheap because it needs nothing but the baseline -- but that’s also its weakness: it has no idea how the project actually unfolded before the event, including any re-sequencing, logic changes, or acceleration that really happened.

Time Impact Analysis (TIA) instead takes the schedule update recorded immediately before the delay event occurred -- the network as it stood, with real progress and any legitimate logic changes already reflected -- and inserts the same fragnet into that network before recalculating. It’s more defensible because it reflects the project’s true condition at the moment of the event, at the cost of needing a good contemporaneous update to start from.

The Project: Meadowbrook Elementary Replacement

A fictional ten-activity sequence for replacing an aging elementary school building, expressed in calendar days from notice-to-proceed (Day 0). The baseline is a single driving chain -- every activity here is critical, with zero float, for a planned Day-160 substantial completion.

What Actually Happened by the Day-119 Update

Real projects rarely track their baseline exactly. By the monthly update dated Day 119, three things had genuinely happened that the baseline never captured: grading finished early, a rebar-delivery overrun on foundations quietly erased that gain, and -- most importantly for this comparison -- the construction manager and contractor legitimately agreed to fast-track MEP rough-in (H) once the envelope (G) was underway, changing that relationship from Finish-to-Start to Start-to-Start plus a 10-day lag instead of waiting for G to fully finish. None of that is in dispute; it’s just what the contemporaneous record shows.

Net effect: as of Day 119, the project’s forecast completion is Day 152 -- eight days ahead of the Day-160 baseline -- almost entirely because of the legitimate G→H fast-track, not because the work itself sped up.

The Disputed Event

On Day 120, the electrical subcontractor exposes a live underground duct bank during MEP rough-in that isn’t shown on any utility drawing, directly conflicting with the new interior utility routing. Design coordination, hand-excavation, and rerouting are required before the remaining rough-in and any interior finishes can proceed -- a 20-calendar-day fragnet: “Duct bank conflict resolution.” Both analyses below insert this exact same 20-day fragnet as a new predecessor to Interior Finishes (I) and successor to MEP rough-in (H). Only the network it’s dropped into differs.

Running It as Impacted As-Planned

IAP ignores everything in the Day-119 update table above. It goes back to the original baseline logic -- H finishing Day 135, strictly Finish-to-Start from G -- and inserts the fragnet there. H still finishes Day 135 (baseline), the fragnet runs Day 135–155, Interior Finishes (I) shifts to Day 155–175, and Final Inspections (J) shifts to Day 175–180.

Recalculated completion: Day 180 -- a straight 20-calendar-day extension off the Day-160 baseline, exactly equal to the fragnet’s own duration, because the baseline chain has zero float anywhere for the fragnet to eat into and no fast-track logic to offset it.

Running It as a Time Impact Analysis

TIA starts from the Day-119 update instead -- the network that already reflects H’s real fast-tracked finish on Day 127 and a pre-event forecast completion of Day 152. The same fragnet is inserted after H’s actual/forecast finish: Day 127–147, pushing Interior Finishes to Day 147–167 and Final Inspections to Day 167–172.

Recalculated completion: Day 172. Measured against that update’s own pre-event forecast (Day 152), that’s the same 20-day shift -- the fragnet duration didn’t change. But measured against the original Day-160 contract completion date, it’s only a 12-calendar-day net extension, because 8 of those days were already legitimately banked before the event ever happened.

Side by Side: Why the Two Answers Disagree

Neither run made an error. Both correctly added a 20-day delay to whatever schedule they started from. The disagreement is entirely about which starting schedule is the right one to measure entitlement from -- and that question is exactly what separates these two methodologies. IAP is silent on the point by design; TIA exists specifically to answer it.

Frequently Asked Questions

Is Impacted As-Planned ever the right method to use?

Yes -- it's still appropriate when no reliable contemporaneous updates exist to build a Time Impact Analysis from, for early conceptual estimates of exposure, or when a contract specifically calls for it. Where good monthly updates exist, though, most forensic schedulers and many tribunals treat TIA as the more defensible method precisely because it doesn't ignore real progress.

Why did the same 20-day fragnet produce two different final numbers?

The fragnet's own duration never changed -- the disputed event was kept identical on purpose. What changed was the schedule it got inserted into. The baseline network in the IAP run has no memory of the 8 days of real, legitimate schedule gain the project had already banked by the time the event hit; the Day-119 update used for the TIA run does.

Which number should actually be used to extend the contract completion date -- 20 days or 12?

The 12-day figure from the Time Impact Analysis is the more defensible one to adjust the contract date by. It reflects where the project genuinely stood -- including a legitimate, already-agreed logic change -- immediately before the event occurred. The 20-day Impacted As-Planned figure is blind to the 8 days of real gain and overstates the entitlement in this example.

Does TIA always produce a smaller extension than IAP?

No -- it depends entirely on whether the project was running ahead of or behind its baseline pace when the event occurred. Here the contemporaneous update showed the project 8 days ahead, so TIA's answer came in lower. If the same project had instead been running 8 days behind for legitimate, excusable reasons, TIA would have produced a larger extension than IAP, not a smaller one.