A number of methods have been developed for analysing the effect of delay on project completion, all utilising CPM schedules prepared at the commencement of — and during — the project. The four most commonly used methods are the As Planned Impacted Program (APIP), the As Built But For (ABBF), Windows Analysis, and Snapshot Analysis. Each has distinct advantages, drawbacks, and appropriate contexts of use.
Prerequisite: Any schedule errors, scope omissions, or missing logic must be corrected before a proper delay assessment can commence. The quality of the analysis is entirely dependent on the quality of the schedule data.
1. As Planned Impacted Program (APIP)
The impacted as-planned analysis involves inserting delay events into a baseline or as-planned schedule to determine the hypothetical impact of those events. The method modifies the baseline schedule by adding new activities and logic to represent delay events. The difference between the project completion date in the impacted schedule and the original as-planned schedule quantifies the delay.
Best suited for:
Situations where limited as-built records are available, or as a preliminary estimate of entitlement.
Advantages
Simple to perform
Does not require an as-built schedule
Quick to produce a preliminary estimate
Drawbacks
Considered a hypothetical model — does not rely on as-built data
Does not account for how the project actually evolved
May be challenged as overly simplistic in litigation
2. As Built But For (ABBF)
The ABBF analysis is more complex than APIP because it requires as-built dates as historical events fixed in time, and accurate records of all events. The analyst creates a logic network that calculates start and finish dates identical to actual historical dates — then removes the delay events to demonstrate what the project would have looked like "but for" those events.
The analytical steps required are:
Prepare a comprehensive list of all changes or unanticipated events that occurred and relate them to specific points in time
Prepare an accurate written description of each major change or event
Establish whether each event is compensable and/or excusable
Document the contractual bases for each event
Obtain hard copies and electronic copies of the baseline programme and all subsequent revisions
Establish or confirm as-built dates for critical and near-critical activities over the life of the works
Update the last recorded "as-planned" project to reflect the complete history through to completion
Identify differences between planned and actual critical path performance
Prepare a table comparing as-planned and as-built start/finish dates and lag durations
Determine the extent of variances in calendar days for activities that started late, finished late, started early, or finished early
Establish the cause or causes for each variance
Determine the responsibility for each change or unanticipated event
Incorporate responsibility information into the comparison table (step 9)
Create a discrete activity for each delay and incorporate it into the network logic
Adjust the duration of the delayed activity so that the combined duration of the imposed delay and the delayed activity equals the as-built duration
Simulations can then be run by setting to zero the duration of events, separately for: Owner-caused delays / Contractor-caused delays / All delaying events / Neutral delays.
Principal benefit
Produces a method by which the as-built programme can be compared against what would have transpired had none of the claimed events occurred. Allows "what if" scenarios.
Drawbacks
The extraction of arbitrarily established delays from the as-built programme can conceal the Contractor's own delays. The critical path at completion may not represent the critical path during construction.
3. Windows Analysis
The Windows Analysis is based not on the entire Contract period but on particular windows of time — looking at events that affected progress within each window sequentially. Within each window the analysis can be carried out by any suitable method (such as ABBF). The programme which closes each window represents both the as-built programme at that time and the as-planned programme for the next window.
The ten steps of Windows Analysis:
Locate the original baseline programme and all as-planned programmes and updates — identify original and actual completion dates
Determine the window time periods to be analysed
List activities on the first as-planned programme programmed to start within the first window
Using contemporaneous records, identify actual start and finish dates for those activities
Analyse the dates and determine the delay or advancement of each activity
Establish the cause(s) for each delay and determine responsibility from project documentation
Verify that the programme status at the end of the first window matches the opening status of the next window
Repeat steps 3–7 until all windows have been analysed
Calculate the delay to the entire project by adding the net delays and advancements across all windows
Summarise results and apportion responsibility
Principal advantage:
Because each window represents a limited time period, it affects a relatively small number of activities — making the interpretation of results more convincing than analyses spanning hundreds of activities across the entire Contract period.
4. Snapshot Analysis
The Snapshot Analysis is a programme analysis technique designed to identify and quantify schedule impacts by analysing the status of the project at the time critical events occurred. The as-built history of the project is established up to the event, the programme is recalculated, and the as-planned (uncompleted) portion is used to forecast the outstanding work.
The method of analysis:
At the start of analysis, identify the as-planned network and gather relevant records and documents
Identify the first event — categorise as excusable and compensable / excusable but non-compensable / neither compensable nor excusable
Identify the dates on which each event occurred
Using progress data, update and re-analyse the network and recalculate the critical path
Using the updated network, simulate the relevant event by adding the delay activity — the difference between the forecast end date and the newly calculated finish date is the potential delay
Once all activity delays are quantified, origins, causes, and responsibility are then researched and apportioned.
Retrospective Longest Path Analysis
In this approach, the focus lies on determining the critical path as it actually unfolded during the project — distinct from the contemporaneous or planned critical path. The delay analyst:
Establishes or verifies a detailed as-built schedule
Traces back from the project's completion date to identify the longest continuous path — the retrospective as-built critical path
Investigates project records (site diaries, correspondence, meeting minutes, interviews) to understand the causes behind identified critical delays
Key limitation:
This method has a relatively constrained ability to accommodate shifts in the critical path during project execution. It may not fully capture instances where the critical path changed significantly during construction.
Productivity Loss — MCAA Categories
The Mechanical Contractors Association of America (MCAA) identified 16 categories of productivity loss that are widely recognised in delay claims involving labour inefficiency:
Stacking of trades (concurrency of workforce labour)
Poor morale and attitude
Reassignment of manpower
Crew size inefficiency
Concurrent operations
Dilution of supervision
Learning curve
Errors and omissions
Beneficial occupancy
Joint occupancy
Site access
Logistics
Fatigue
Ripple effect
Overtime
Season and weather change
Lesson 3 Quiz — Delay Analysis & Claims
Select the best answer for each question.
Q1. The primary purpose of delay analysis in construction projects is to:
Q2. Common CPM-based methods used in delay analysis include:
Q3. A well-documented contemporaneous notice:
Q4. Excusable delays might include:
Q5. The purpose of a delay claim is to:
Discussion & Scenario Questions
Q6. Explain the difference between an excusable delay and a non-excusable delay in a construction project, and give one example of each.
Q7. Describe two key elements a contractor should include in a well-documented delay claim to maximise their prospects of recovery.
Q8. A construction project experiences a delay due to a labour strike impacting several key subcontractors. The strike was unforeseen and lasted two weeks. The contractor believes this is an excusable delay and intends to submit a claim for additional costs. What specific steps should the contractor take to strengthen their claim position? Consider your answer in terms of documentation, notification, programme evidence, and entitlement analysis.