June 25, 2026 · Updated October 13, 2026

Change Orders in Construction: How They Work in Ontario

A change order in construction is a signed agreement that changes the work, the contract price, the contract time, or any combination of the three after the contract has been signed. On a fixed-price project it’s prepared by the Consultant (the architect or engineer administering the contract) and signed by both the owner and the contractor. On most Ontario building projects the rules for it come from Part 6 of CCDC 2 – 2020, the standard Stipulated Price Contract, which also provides a Change Directive for when the work has to proceed before the price is agreed.

This article is for the owner who will be signing them. It covers the change process under CCDC 2, where change orders come from, how to price and approve one, and how changes are paid and held back under Ontario’s Construction Act. It isn’t legal advice, and your contract may amend any of the clauses described here.

How a change order works under CCDC 2

Part 6 of CCDC 2 – 2020, Changes in the Work, has six general conditions: GC 6.1 Owner’s Right to Make Changes, GC 6.2 Change Order, GC 6.3 Change Directive, GC 6.4 Concealed or Unknown Conditions, GC 6.5 Delays and GC 6.6 Claims for a Change in Contract Price (CCDC 2 – 2020 table of contents). Our guide to CCDC 2 for owners covers the rest of the contract.

The owner’s right to make changes

GC 6.1 lets the owner, acting through the Consultant, add, delete or revise work by Change Order or Change Directive without invalidating the contract, and change the Contract Time by Change Order. It also says the contractor shall not perform a change in the Work without a Change Order or a Change Directive. So a verbal instruction on site or an email from a tenant isn’t, on its own, a change the contract recognizes.

From a proposed change to a quotation

Under GC 6.2 the Consultant gives the contractor a written description of the proposed change, and the contractor responds promptly with a method or amount of adjustment to the Contract Price and Contract Time, if any, in a form that can be reasonably evaluated. Nothing in the contract has changed yet; you’re looking at a price.

Signing the Change Order

When you and the contractor agree on the price and time, or on the method of working them out, GC 6.2 says the agreement takes effect immediately and is recorded in a Change Order. The contract defines a Change Order as a written amendment prepared by the Consultant and signed by the Owner and the Contractor, stating their agreement on the change in the Work and any adjustment to the Contract Price and Contract Time. Scope, price and time are settled together, which makes it the cleanest outcome.

When the price isn’t agreed: the Change Directive

When the work can’t wait for the price, under GC 6.3 you, through the Consultant, issue a Change Directive, and on receipt the contractor shall proceed promptly with the change. The price is worked out afterwards. The rules worth knowing before you issue one:

• It can only direct a change within the general scope of the Contract Documents, and it can’t be used to change the Contract Time alone.
• Unrelated changes shouldn’t be grouped into one Change Directive.
• The price is adjusted on the contractor’s actual costs attributable to the change, plus the contractor’s percentage fee on a net increase. A net decrease reduces the price with no adjustment for fee.
• GC 6.3.7 lists the costs that count, limited to those that contribute directly to carrying out the change, a limit tightened in the 2020 edition (MLT Aikins, April 2021).
• The contractor keeps detailed cost records and copies them to the Consultant, and you’re entitled to reasonable access to the contractor’s documents for valuing the change.
• The undisputed value of the work done is eligible for progress payment while the final amount is open, and once price and time are agreed the Change Directive is recorded in a Change Order.

The Change Directive keeps a project moving. The trade-off is that you commit to the work before you know what it costs, so it works best when cost records are kept daily and reviewed while the work is happening.

Concealed or unknown conditions

GC 6.4 covers conditions at the site that differ materially from what the Contract Documents show, or from what’s normally found in that type of work, excluding weather. Whoever discovers the condition gives Notice in Writing to the other party before it’s disturbed, and no later than 5 Working Days after first seeing it (Clark Wilson’s commentary on GC 6 describes the same notice). The Consultant investigates and makes a finding. If the condition is materially different and changes the contractor’s cost or time, the owner issues a Change Order or Change Directive; if not, the Consultant tells both parties in writing. The clause works both ways, so a condition better than shown can reduce the price.

Delays and the Contract Time

Under GC 6.5, if the owner, the Consultant or anyone they engage delays the contractor contrary to the contract, the Contract Time is extended and the contractor is reimbursed reasonable costs. For delays outside anyone’s control, such as labour disputes, fire or abnormally adverse weather, time is extended but costs aren’t paid. No extension is made unless the contractor gives the Consultant Notice in Writing of the cause within 10 Working Days after the delay starts.

Claims for a change in Contract Price

GC 6.6 covers a claim by either party when the two sides see an event differently. The claiming party gives timely Notice in Writing of intent to claim, mitigates, keeps records and submits a detailed account within a reasonable time. The Consultant’s findings follow in writing within 30 Working Days of receiving the claim unless the parties agree otherwise, and a finding either party won’t accept goes to the dispute steps in Part 8.

“Timely” and “reasonable time” are open words, and many owners tighten them in supplementary conditions. The City of Waterloo’s supplementary conditions to CCDC 2 – 2020 (May 2023), for example, require the notice within 30 Working Days of the start of the work giving rise to the claim.

Change Order vs Change Directive vs Supplemental Instruction

CCDC 2 – 2020 defines three written instruments that change what the contractor builds. The difference decides whether the price moves.

The contract defines a Supplemental Instruction as an instruction, not involving adjustment in the Contract Price or Contract Time, consistent with the intent of the Contract Documents, and under GC 2.2 the Consultant issues them as the work proceeds. They clarify; they don’t add scope. If the contractor reads one as new work, the right response is a request for a Change Order or a notice under GC 6.6, and the Consultant decides, ideally before the work is done.

Changes on construction management projects

Under CCDC 5B the construction manager carries out the work on a cost basis plus a fee, and the 2025 edition uses a Change Order to elect a guaranteed maximum price or stipulated price option (Gowling, July 2025). Under CCDC 5A you hold each trade contract yourself, normally on CCDC 17. Our comparison of CCDC 5A vs 5B covers cost control under each, including what a change does to a GMP.

Where change orders come from, and how to prevent them

Almost every change order traces back to one of four sources. Contractors pricing changes is normal and expected; the contract assumes it. What the owner controls is how many changes there are, when they arrive and how well they’re documented.

Design gaps

The drawings and specifications were incomplete, uncoordinated or unclear, and the contractor is pricing the difference between what was drawn and what the building needs: ductwork that doesn’t fit the ceiling space shown, a structural detail that doesn’t match the architectural one, a specification section never written. On projects tendered before the design was finished, this is often the largest category.

To reduce it, tender on complete, coordinated documents and budget the design time to get there. Have the documents reviewed before tender by someone looking for gaps and conflicts, and answer bidder questions by addendum so the answers are priced competitively. We’ve written about this stage in the real cost of skipping preconstruction.

Site conditions

The ground or the existing building held something the documents didn’t show: soil or groundwater, contamination, buried services, or structure that differs from the record drawings. GC 6.4 exists for this, and on renovation work some of it is unavoidable.

To reduce it, commission geotechnical investigation, surveys and utility locates during design, and on renovations fund selective exploratory demolition before tender. Put what you found into the tender documents, so the contractor prices known conditions and GC 6.4 is left for genuine surprises. Investigation during design is usually a modest cost next to a concealed condition found during construction, which is priced without competition and often adds time.

Owner decisions

You changed the scope: a tenant’s requirements shifted, a lender asked for something, or a finish was upgraded. That’s your right under GC 6.1, and plenty of these changes are worth making. They become costly when they’re late, because a change made after the work is in place usually means removing and redoing it.

To reduce it, lock major decisions (layouts, equipment, finishes, tenant requirements) before tender pricing, and keep a decision schedule tied to the construction schedule, as described in the quiet cost of slow decisions. Budget for your own changes separately from the contingency held for unknowns.

Errors and omissions

Someone got something wrong: a dimension, a quantity, a discontinued product. This is usually the smallest category on well-run projects and it’s never zero. Review time in the design schedule, including a coordination review between disciplines, is what reduces it.

What drives change volume

We don’t quote a typical change-order percentage, because we haven’t found a Canadian source that publishes one holding across project types. What drives the number is predictable. Change volume tends to be higher on renovations and heritage work, on projects tendered from incomplete documents, on fast-tracked projects where design continues during construction, and where the owner’s requirements are still moving. It tends to be lower on new construction with complete documents, early investigation and decisions made on time. Size your contingency with these factors in mind; how much contingency is enough sets out how.

Pricing and approving a change

A change order is a small contract priced without competition, so most of the work is in agreeing the rules before tender and checking each change against them. Our article on five questions to ask before you sign covers the contract side.

What backup to ask for

Ask for every quotation to be broken down the same way:

1. Scope: tied to the drawing, sketch or instruction that started it, with exclusions stated.
2. Quantities: measured from the drawings, with the takeoff available on request.
3. Labour: hours by trade and the rates applied, matching any rates schedule in the contract.
4. Materials and equipment: quantities and unit costs, with supplier quotes for significant items.
5. Subcontractor quotes: the subcontractor’s own breakdown, not only its total.
6. Credits: work no longer needed, priced and deducted.
7. Markup: applied as the contract sets it, shown separately.
8. Time: the effect on the Contract Time, or a statement that there is none.

Waterloo’s 2023 supplementary conditions write this into the contract, requiring a written quotation that identifies each amount for transportation, labour, products, construction equipment and services, with subcontractor backup and HST shown separately. If a quotation arrives as a lump sum, ask for the breakdown before reviewing it.

Markups and unit prices

Set markups in the supplementary conditions before bids come in. Waterloo’s version allows a maximum of 15% on the first $100,000 of change orders and 10% after that, with 5% for the general contractor on a subcontractor’s change, and makes those markups the only compensation for overhead, profit, supervision and office costs on the change. Your numbers may differ; agree them once, at tender.

Ask for tendered unit prices for work likely to vary, such as rock excavation or additional outlets. Waterloo’s conditions apply the tender unit prices wherever a change includes equivalent items, and those prices were set in competition. For Change Directives, owners often list what the cost can’t include; Waterloo excludes head office overhead, capital expenses, and project manager and superintendent wages where the Contract Time isn’t extended.

Price the time with the cost

Ask for the time impact to be priced with the cost and recorded in the same Change Order. A Change Order signed with “time to be determined” leaves the schedule open, and open items tend to come back together near the end of the job as a delay claim. Waterloo’s conditions allow no claim for time, delay or remobilization on a change unless it’s set out in the Change Order or Change Directive.

Who reviews a change

Two reviews are involved, needing different skills:

• Entitlement and scope. Is this actually a change to the Contract Documents, or was it already shown? The Consultant is the first interpreter of the Contract Documents under GC 2.2, so ask for that finding before anyone reviews the price.
• Price. Are the quantities, hours, rates and markup right? This is estimating work for a cost consultant, quantity surveyor or owner’s rep with estimating experience, the same skill set as independent estimating, and the breakdown reads like the one in reading a construction estimate.

Set a turnaround

Write turnaround times into the contract: the contractor quotes within a set number of Working Days of a request, and you decide within a set number of Working Days of the quote. Slow approvals are one of the main reasons work gets done before it’s authorized, so if changes are sitting unanswered, start with the approval side.

Change orders, payment and holdback in Ontario

CCDC 2 – 2020 defers to provincial payment law, which in Ontario is the Construction Act. The Act defines “contract” to include any amendment to it (s. 1(1)), so a signed Change Order is part of the contract for payment, holdback and lien purposes.

Approved changes go into the progress claim

Change Order work is included in progress claims (GC 6.2), and so is the undisputed value of Change Directive work (GC 6.3). In Ontario the monthly progress claim is a proper invoice, given monthly unless the contract says otherwise (s. 6.3(1)), and it must identify the contract or other authorization under which the work was supplied (s. 6.1(1), para. 3). On a change, that’s the Change Order or Change Directive number. Ask for changes to be shown as separate lines so each can be checked against what was approved.

The prompt payment clock

You pay a proper invoice within 28 days of receiving it (s. 6.4(1)). To dispute some or all of it, you give a notice of non-payment in the prescribed form within 14 days, stating the amount not being paid and all the reasons (s. 6.4(2)); the rest is still due within the 28 days (s. 6.4(3)). Since January 1, 2026, an invoice missing required information is deemed proper unless you notify the contractor within 7 days (s. 6.1(2)). A clause making the invoice conditional on prior certification has no effect (s. 6.3(2)), so the Consultant’s review of the changes on each claim has to fit inside the 14 days.

Holdback applies to change work

You retain a holdback of 10% of the price of services and materials as actually supplied under the contract (s. 22(1)), and that includes change work: a $40,000 Change Order carries $4,000 of holdback. Since 2026 holdback is also released annually on many contracts (s. 26), which our CCDC 2 guide explains.

Unapproved and disputed changes

When a claim includes a change you haven’t approved, or values a Change Directive higher than you think is right, use the notice of non-payment. Give it within the 14 days, name the items and amounts, and give your reasons, for example that the work was done without a Change Order or Change Directive contrary to GC 6.1.2, or that the quantities aren’t supported. Pay the undisputed balance on time.

If that doesn’t settle it, either party can go to adjudication under Part II.1 of the Act. Since 2026 the eligible matters are set by regulation and include scope of work disputes, time extensions, delay and impact claims and changes to the contract price (Pallett Valo via Mondaq, March 2026). Adjudicators work from documents, so the change record, the notice and the Consultant’s findings carry the case.

Read the trend, not just the total

Tracking each change by cause, not only the running total, tells you why the contingency is being spent while there’s still time to act. Keep one log, updated weekly and reviewed at every site meeting:

Read the distribution monthly. A run of design-gap changes points to the documents, and is worth a coordination review of the packages still to be built. A run of owner changes points to the decision schedule. Early site-condition changes are worth checking against what was investigated before tender. Then compare approved plus anticipated changes against the contingency left; if anticipated changes are growing faster than the work is progressing, revisit the contingency. How much contingency is enough covers tracking the drawdown.

Frequently asked questions

What’s the difference between a change order and a change directive?

A Change Order records an agreed change: scope, price and time are settled and both parties sign. A Change Directive is signed by the owner when the work has to proceed before the price is agreed. The contractor proceeds promptly and keeps cost records, and the price is valued afterwards on actual cost plus the contractor’s fee. Once agreed, it’s recorded in a Change Order (CCDC 2 – 2020, GC 6.2 and 6.3).

Can a contractor refuse a change order?

A contractor can decline to sign a Change Order, because it records an agreement on price and time. Under CCDC 2 the owner can then issue a Change Directive, and the contractor must proceed promptly with the change as long as it’s within the general scope of the Contract Documents (GC 6.3). A change well outside the original scope is a different matter, worth discussing with your Consultant and lawyer.

Should I pay for changes performed without approval?

Start with the contract. CCDC 2 says the contractor shall not perform a change without a Change Order or Change Directive (GC 6.1.2), so work done without one isn’t automatically payable. If you dispute it on a progress claim, give a notice of non-payment within 14 days. Then look at why it happened, because unauthorized work often follows slow approvals.

Who should review change-order pricing?

Two people. The Consultant confirms whether the work is actually a change to the Contract Documents. Someone with estimating experience checks the quantities, hours, rates and markup against the contract, whether a cost consultant, a quantity surveyor or an owner’s rep. Reviewing change pricing is a standard part of our owner’s representation work.

Getting changes under control on your project

Before tender, the useful steps come before the first change exists: complete documents, early investigation, markups and unit prices in the supplementary conditions, turnaround times in the contract, and a decision schedule. Already on site, start the cause-coded change log.

We’ve administered change processes for 20+ years across office, residential, retail and industrial work, with experience built at PCL Constructors and Oxford Properties. We review supplementary conditions before tender, check change pricing during construction and set up change logs that report against contingency, as part of our construction consulting work. If your change log is growing faster than you expected, send it to us and we’ll go through it with you.