What should an Ontario deck contract say about changes mid-job?

A deck contract in Ontario should spell out how changes are handled before work starts, because the Consumer Protection Act, 2002 gives you a specific protection once a price is on paper. If the contract includes an estimate, the supplier cannot charge more than 10 per cent above it. That rule applies to the estimate as written, so what the estimate includes and excludes matters as much as the number itself.

If the contract was signed at your home or anywhere other than the supplier's place of business or a market or trade fair, it is a direct agreement under the Consumer Protection Act, 2002. A direct agreement where the total potential payment exceeds $50 must be in writing and delivered to you, and you may cancel it without giving any reason within 10 days of receiving that written copy. Make sure you actually receive the written contract, not just a verbal confirmation, so that 10-day window is clear.

For changes that come up during the job, the contract should describe:

• what triggers a change order (a scope addition, a site condition discovered after digging, a material substitution)
• how a change order is documented, priced and approved in writing before the work proceeds
• which party is responsible for any permit amendment if the change affects the approved drawings

The Construction Act treats a deck as an improvement, and it generally requires a 10 per cent holdback on each payment. Get advice for your situation on how that applies to your contract and payment schedule. An owner pays a proper invoice no later than 28 days after receiving it. Knowing those timelines before you sign helps you structure progress payments so you are not paying ahead of completed work.

One practical point: the contract should list every item that was discussed but priced separately or excluded entirely. Published Ottawa and Ontario builder prices, read in September 2026, show that some packages exclude railings and steps. If removal of an existing deck, permit drawings, the foundation type, stairs or guards were quoted separately or left open, the contract should say so explicitly, with a note on how each will be priced if needed.

The Construction Act also gives contractors and subcontractors lien rights against your property. A contractor's lien is tied to timelines connected to substantial performance, completion, abandonment or termination of the contract. Understanding when those periods run is another reason to have the payment and completion milestones written clearly.

You can request a match with local deck builders through the form on this page; the builders are listed in the Ottawa Construction Network directory.

Ask each builder to show you the full written list of what is and is not included in their quoted price, so you can see exactly where a change order could add cost before you commit.