A quote is a document about risk allocation, and most owners read it as a document about price. Two weeks before a tariff change is a good moment to correct that.
On standard construction contracts, the answer is usually unfavourable to the owner. Analysis from Gowling WLG notes that under stipulated-price CCDC forms, general condition 10.1.2 provides that any increase or decrease in the contractor's costs from changes in taxes and duties after bid closing adjusts the contract price accordingly — so the contractor is entitled to pass a tariff increase through. The same analysis is blunt about the escape hatch owners tend to reach for: an unexpected cost increase, tariffs included, does not amount to force majeure under Canadian law, and courts have held that a more expensive obligation is still an obligation. Most household renovations do not run on CCDC paper, but the logic tells you what clause to look for and what to negotiate before signing.
Residential owners have a second layer of protection that commercial buyers do not, and it is provincial rather than federal. In Ontario, Consumer Protection Ontario states that where a written estimate forms part of the contract, the final price cannot exceed it by more than 10 per cent unless the owner has agreed to new work or a new price and signed a change; any renovation contract over $50 must be in writing, and contracts signed in the home carry a ten-day cooling-off period.
The exception matters as much as the rule. Analysis by Miller Thomson notes that the cap falls away once the consumer agrees to an amended estimate, and that Alberta's equivalent caps overruns at the lower of 10 per cent or $100. In practice this means a homeowner who signs a revised estimate in October to absorb a tariff increase has waived the very protection that would have contained it. Other provinces run their own regimes, so verify your own rather than assuming a national rule.
Get the written estimate this week, not next month. A written estimate that forms part of the contract is worth materially more than a verbal quote once prices start moving, and it is the single cheapest piece of protection available in the runway.