Part of the Ontario construction contracts guide for owners.
Few issues cause more trouble in delay claims than concurrent delay. The owner was late with a design decision, and the contractor's steel was late at the same time. Both delays touched the critical path. Who gets more time? Who gets paid? Can the owner still claim liquidated damages? On large Ontario projects, the answer can swing hundreds of thousands of dollars. Canadian law gives less certainty than most owners would like.
This guide explains what concurrent delay is, how international guidance and Canadian courts approach it, and what owners can do in their contracts and records to protect themselves.
What counts as concurrent delay
Not every pair of overlapping delays is concurrent. The term has a specific meaning.
The Society of Construction Law's Delay and Disruption Protocol (2nd edition, 2017) describes "true" concurrent delay as two or more delay events happening at the same time, one the owner's risk and one the contractor's, with both affecting completion. It notes that true concurrency is rare. The more common situation is what it calls concurrent effect: the events happen at different times, but their effects on completion are felt at the same time.
In both cases, the Protocol says each event must be an effective cause of delay to completion. A contractor delay to an activity with plenty of float isn't concurrent with an owner delay on the critical path. It's just a contractor delay that didn't matter.
AACE International's Recommended Practice 29R-03 sets out similar prerequisites. The delays must be unrelated and independent, the contractual responsibility of different parties, involuntary, and substantial rather than easily curable.
How the SCL Protocol deals with time and money
The Protocol separates two questions that people often run together: does the contractor get more time, and does the contractor get paid for that time?
Time. Under Core Principle 10, where a contractor delay runs concurrently with an owner delay, the contractor's delay should not reduce the extension of time it gets for the owner's delay. The practical effect is that the contractor is relieved from liquidated damages for the concurrent period.
Money. Under Core Principle 14, where delays are concurrent, the contractor should recover prolongation costs only if it can separate the extra costs caused by the owner's delay from those it would have incurred anyway because of its own delay.
The result is often called "time but no money." The contractor is protected from damages for late completion during the concurrent period, but doesn't get paid for its own extended site costs unless it can isolate what the owner's delay added.
The Protocol is widely referenced but it isn't law in Ontario. It applies only if your contract adopts it, or if a tribunal chooses to treat it as persuasive.
View the data
| Situation | Extension of time | Delay costs to contractor | Owner's LDs |
|---|---|---|---|
| Owner delay only | Yes | Yes, if the contract allows | No, for that period |
| Contractor delay only | No | No | Yes, if in contract |
| Concurrent delay | Yes (CP 10) | Separable costs only (CP 14) | No, for that period |
A worked example
Take an illustrative office building scheduled to reach substantial performance in week 60. Two things go wrong:
- The owner takes four weeks longer than planned to finalize tenant layouts. Interior fit-out on two floors, a critical activity, slips four weeks.
- Over the same period, the contractor's elevator supplier delivers three weeks late. Elevator installation is also on the critical path, because elevators have to be certified before occupancy.
The project finishes in week 64. The four-week delay has two causes that overlap for three weeks.
Under a "time but no money" approach, the contractor gets a four-week extension. That relieves it of liquidated damages for all four weeks. It can claim extended site costs for the one week where only the owner's delay was operating. For the three overlapping weeks it gets time but no money, unless it can show costs that the owner's delay alone caused.
Under an apportionment approach, the parties or a tribunal might split responsibility for the three overlapping weeks based on each delay's contribution. The answer depends heavily on the evidence.
Under an owner-favourable clause, the contractor might get no extension for the overlapping weeks. That leaves it exposed to liquidated damages, subject to how a court reads the clause and the prevention principle.
The same facts produce three different financial outcomes. That's why the contract wording deserves attention before tender, not after the dispute starts. It's also why owners should insist that each of these delays is notified and analyzed when it happens, while the facts are still easy to establish.
What Canadian courts have said
Canadian case law on concurrent delay is thinner than in the United Kingdom or the United States. Commentators have long noted that the principles aren't settled. In a column for On-Site Magazine, a Borden Ladner Gervais construction lawyer observed that Canadian courts have generally apportioned delay damages based on each party's contribution, and may split responsibility equally when contributions can't be measured.
The most-cited recent Ontario decision is Schindler Elevator Corporation v Walsh Construction Company of Canada, 2021 ONSC 283. It arose from the redevelopment of Women's College Hospital in Toronto. Walsh, the general contractor, counterclaimed against its elevator subcontractor, Schindler, for delay. Walsh relied on a delay analysis showing concurrent delays by several subcontractors.
A few points from the decision, as summarized by commentators, are useful for owners:
- Overlapping delays can still be concurrent. The court accepted that true concurrency, where delays start and end at exactly the same time, is rare. Concurrent delays are more commonly experienced as overlapping events.
- Causation must be proved. The party claiming delay damages has to show that the other party's delay actually caused its loss. Walsh's claim largely failed because its evidence didn't establish that Schindler's delay drove overall project completion.
- Expert evidence matters. Commentary from Miller Thomson notes that the outcome turned heavily on the reliability of the delay analysis. Without a credible critical path analysis, the claim couldn't be apportioned.
The practical lesson is the same one the international guidance teaches. Concurrent delay arguments are won and lost on schedule evidence and contemporaneous records, not on labels.
Why contracts matter more than case law
Because the law is unsettled, the contract usually decides the outcome. Standard forms such as CCDC 2 deal with delays caused by the owner and delays beyond the contractor's control, but they don't set out a detailed concurrent delay regime. Owners who want certainty need to address it in their supplementary conditions.
Common approaches include:
- Time but no money for concurrent periods, consistent with the SCL Protocol.
- Apportionment, where time and costs are split in proportion to each party's contribution.
- No time for concurrent periods, which is more owner-favourable but must be drafted carefully. Clauses that try to deny any extension where the owner contributed to delay can run into the prevention principle, the idea that a party can't benefit from its own delay.
Exclusion and limitation clauses are generally enforceable between sophisticated commercial parties, but courts read them narrowly against the party that drafted them. A vague concurrent delay clause may be read as not covering the delay that actually happened. Define the term precisely and get legal advice on the drafting.
The records that decide concurrent delay disputes
On programs we've supported, the side with the better records usually wins the concurrency argument. The records that matter most:
- Monthly schedule updates in native format, showing the critical path at each point.
- Delay notices and responses, with dates.
- An owner decision log showing when each decision was requested, when it was due and when it was made.
- Daily reports and site photos showing what crews were actually doing.
- Procurement tracking for long-lead items, including the contractor's own supply chain.
- Meeting minutes that record schedule discussions, recovery plans and agreed resequencing.
If the owner's own delays are well documented and promptly resolved, and the contractor's are recorded as they happen, a concurrency argument raised at the end of the project has far less room to grow.
What owners should do
- Decide your concurrent delay position before tendering. Choose an approach and write a clear definition into the supplementary conditions, with legal advice.
- Require prospective analysis of each delay. Ask for a time impact analysis against the current update when each event is notified, so concurrency is assessed while the facts are fresh.
- Clear your own delays fast. Every owner delay left unresolved is a potential concurrent delay later. Track owner decisions as carefully as contractor activities.
- Record contractor delays when they happen. Note them in meeting minutes and update narratives. A contractor delay that wasn't documented at the time is hard to prove a year later.
- Ask for costs to be separated. When a prolongation claim covers a period with contractor delays, ask the contractor to show which costs the owner's delay actually added.
The bottom line
Concurrent delay is less about legal theory than about evidence. Canadian courts have shown they'll look hard at whether each delay really drove completion and whether the claimant can prove what it cost. Owners who define the rules in the contract and keep strong contemporaneous records are in a far better position than those who rely on the law to sort it out.
Want help setting up your contract or responding to a concurrency argument? Book a 30-minute call with Benjamin R. Consulting.
Sources: Society of Construction Law, Delay and Disruption Protocol, 2nd edition (2017), Core Principles 10 and 14; AACE International, Recommended Practice 29R-03, Forensic Schedule Analysis (2011); Miller Thomson LLP, Concurrent delays in construction projects: How Canadian courts decide who pays (November 26, 2025); Diales, Concurrent delay and Schindler v Walsh: alignment in Canada; On-Site Magazine, Concurrent delay remains thorny issue; Norton Rose Fulbright, Relief provisions in Canadian construction contract suites. This article is general information, not legal advice. Get legal advice on your contract and specific circumstances.