Check the drawing revision, re-measure the two or three lines carrying most of the value, and date every unit price. An assembled estimate is internally consistent and externally unchecked.
Key takeaways
Check it against the drawing revision it was built from, re-measure by hand the two or three line items that carry most of the value, and confirm the date and region on every unit price. Then read the exclusions as if you were the customer looking for a way to be surprised.
This matters more in Canada than a generic estimating checklist suggests, because in Ontario an estimate included in a contract is close to binding: ministry guidance for home renovation and roofing businesses states that you cannot charge more than 10% above the estimated cost unless the customer required additional or different goods or services and you have signed a change to the contract. A machine-assembled number you did not check is a commitment you did not read.
1. Which drawings. Confirm the revision, date and sheet list the takeoff came from. An estimate built on a superseded set is wrong in a way no amount of arithmetic checking will reveal.
2. Re-measure the top three by value. Not the top three by quantity. Sort the estimate by extended cost, take the three largest lines, and measure them independently. If all three land, the method is probably sound; if one is out by a third, stop and rebuild.
3. Date and region every unit price. A rate with no date is not a rate. This is the single most common defect in an assembled estimate, because the tool will happily reuse whatever it was given.
4. Read the exclusions against the specification. Machine-drafted exclusion lists tend to be generic. The exclusions that matter are the ones specific to this job — the temporary heat, the crane time, the abatement, the after-hours restriction in the tenant’s lease.
5. Check the labour assumption. Crew size, productivity and rate. A takeoff can be exactly right and the estimate still wrong because the assumed crew does not exist in your business this month.
6. Confirm sub quotes are in writing and current. And for electrical work in Ontario, that the subcontractor is a Licensed Electrical Contractor — the Electrical Safety Authority notes the seven-digit ECRA/ESA licence number should appear on their vehicles, business cards and estimates.
7. Taxes, allowances and contingency. Check each is present, labelled and not double-counted. Allowances silently converted into fixed prices are a recurring source of disputes.
8. Attach a validity period. See the next section — this is not boilerplate.
9. Check the contract wording separately. The estimate and the agreement are different documents with different rules.
10. Sign it. A person, by name, who has done steps one to nine.
Construction costs do not move as a single number, so an estimate without a date is a bet on the wrong thing. Statistics Canada’s building construction price indexes for the second quarter of 2026 record residential building construction costs up 0.5% and non-residential up 1.4% in the quarter — but at the division level, metal fabrications rose 2.1% and structural steel framing 1.8%, while wood, plastics and composites fell 0.3%. Regionally the spread was wider still, with residential costs up 2.6% in the Québec census metropolitan area and down 0.8% in Toronto in the same quarter.
A steel-heavy job and a wood-frame job priced from the same three-month-old cost base are therefore wrong in opposite directions. Give every estimate an explicit expiry, and re-price stale rates by division rather than with a single blanket uplift.
What the software cannot check for you
Whether the drawings are the current set. It will measure whatever it is given, confidently.
Whether the scope in the estimate matches the scope in the specification — two documents it may never have compared.
Whether your crew can actually build it at the assumed productivity.
Whether the customer understood what was excluded. That is a conversation, and in Ontario the written agreement rules exist precisely because those conversations get remembered differently.
The Ontario guidance also requires a written agreement for any contract worth more than $50, that mid-project scope changes be documented and communicated in writing with both parties signing the changed contract, and that a customer signing at their home has a ten-day cooling-off period, with refunds due within fifteen days of notice of cancellation. That last protection has its own separate teeth: the Consumer Protection Act lets a customer cancel a future performance agreement within one year of signing if they never received a copy meeting the content requirements the Act sets out for it — the same content an assembled estimate has to carry once it becomes part of a contract. Where the commercial form matters, the Canadian Construction Documents Committee publishes standard prime contracts including the CCDC 2 Stipulated Price Contract and the CCDC 4 Unit Price Contract, which allocate measurement and change risk differently.
Our sister firm covers what happens next when the number moves: when a contractor wants more money than the quote and how change order disputes typically play out.
A renovation contractor receives an assembled estimate for a two-storey addition. The review takes eleven minutes and finds three things.
The takeoff was built on the architect’s issued-for-permit set, while the structural revision issued the following week enlarged two openings — caught at step one. The steel lintel line, third largest by value, was priced from a rate carried over from the previous winter — caught at step three, and re-priced because steel-related divisions had moved. And the exclusion list omitted temporary heat, which for a January start is not a detail.
None of those three were arithmetic errors. The arithmetic was perfect, which is precisely the risk: an assembled estimate is internally consistent and externally unchecked until a person checks it.
Scope described in the customer’s language, quantities and units visible, unit prices dated, allowances and exclusions listed plainly, taxes shown, a validity period, and a named person who prepared it. If the customer cannot tell what is not included, the document is not finished.
It can re-run a calculation and flag internal inconsistencies, which is useful. It cannot tell you that it measured the wrong drawing set, because it has no independent knowledge of which set is current. Verification has to come from outside the tool that produced the number.
It depends on how it is presented and what it is attached to, which is a legal question rather than an estimating one. What is clear in Ontario is that an estimate included in a contract carries the 10% limit above, and that changes require signed documentation.
Fix the inputs rather than lengthening the review. Most repeated review findings trace to two causes — undated rates and an unclear current drawing set. Solve those at source and the ten-minute check stays a ten-minute check.
A 30-minute call is enough to tell you whether AI pays for itself here.
