Learning Center
Concurrent Delay: How to Actually Test for It
“Concurrent delay” is one of the most invoked -- and most misapplied -- terms in delay analysis. Two delays overlapping on a calendar isn’t concurrency. Here’s the actual test, worked through step by step on a real two-activity example.
The Real Definition
Concurrent delay exists only when two independent delay events, occurring during the same period, would each on its own have pushed back the project’s critical path by the same amount, over the same window. Both conditions have to hold: each delay has to be independently critical (not just present), and the delayed activities have to be on paths that were each, on their own, controlling the finish date during the overlap.
This is stricter than it sounds. A delay that’s merely happening at the same time as another one, but sitting on an activity with days of float to spare, isn’t concurrent with anything -- it’s just noise that never reached the critical path.
Worked Example: Two Independent Delays, One Window
Two activities, each on their own driving path through different parts of the schedule, both slip during overlapping calendar days:
- Activity A — Structural steel design. The owner takes 18 days to answer an RFI the steel fabricator needs before releasing shop drawings. Steel design is on the critical path throughout this period -- nothing else is driving the finish date. This delay is owner-caused: excusable and compensable.
- Activity B — Site excavation. Unexpected rock is encountered starting day 8, adding 10 days to excavate around it. Excavation is also on the critical path during this stretch -- the steel-design delay hasn’t yet started driving the finish, so excavation is the thing controlling it on its own merits. A differing-site-condition clause makes this excusable but non-compensable (typical for unforeseen subsurface conditions on many contract forms).
| Period | Activity A (Steel Design) | Activity B (Excavation) |
|---|---|---|
| Days 1–10 | Owner design clarification pending (RFI open) | Normal progress |
| Days 8–18 | RFI resolved, work resumes | Unexpected rock encountered during excavation |
| Days 11–18 | Overlap window | Overlap window |
Running the Test, Step by Step
- Isolate each delay’s own critical window. A drives the critical path days 0–18. B doesn’t become independently critical until day 11, once the rock excavation has consumed enough of its own float to start controlling the finish date on its own.
- Find the true overlap. Both conditions -- present and independently critical -- hold only for days 11 through 18. That eight-day window is the actual concurrent delay period.
- Apportion the rest. Days 0–10 are attributable to A alone (owner-caused, compensable). Days 11–18 are concurrent.
Outcome: the contractor is entitled to a full 18-day extension of time (10 days from A alone, plus 8 concurrent days). Compensable delay costs, though, typically apply only to the non-concurrent 10-day portion -- the 8 concurrent days are usually treated as excusable but non-compensable, since the project would have slipped those 8 days from the rock encounter alone even if the RFI had been answered on time.
Why This Is So Often Done Wrong
The most common error is treating any two delays that happened in the same month as concurrent, without ever checking whether each one was actually driving the critical path on its own during that period. Proving true concurrency means tracking the critical path’s own identity across the disputed window -- not just noting that two bad things happened around the same time.
This is exactly what schedule comparison is built to surface. Claims Digger’s comparison engine tracks which activities were actually driving the finish date in each snapshot, including near-critical activities close enough to matter -- turning “were both delays independently critical during the overlap” from a manual reconstruction into something you can see directly. See how it works.
Frequently Asked Questions
- Is concurrent delay the same as two delays happening at the same time?
- No -- that's the single most common misuse of the term. Two delay events overlapping in calendar time isn't concurrency unless each one, independently, would have delayed the project's critical path on its own during that same period.
- What's the usual outcome once true concurrency is established?
- In most U.S. jurisdictions, genuinely concurrent delay -- one excusable/compensable, one non-excusable -- typically results in an excusable-but-not-compensable extension of time: the contractor gets the schedule relief but not the associated delay costs, on the theory that the project would have been delayed anyway by its own non-excusable cause.
- Can concurrent delay exist if the two events are only a few days apart, not exactly simultaneous?
- Yes, under the more commonly applied 'reasonable overlap' approach many courts and boards use -- delays don't need to start on the exact same calendar day, only both need to have been independently critical during a genuinely overlapping window.
Part of the Claims Digger Learning Center. Related reading: Time Impact Analysis, step by step · Full glossary