Construction Mortgage in Canada: Why Your $600,000 Build Only Advances $540,000 Before You Move In

Sunday, 1 November 2026 — the bottom line. A construction mortgage does not hand you the money to build. It reimburses work an appraiser has already certified as finished, less a 10% holdback your province requires. On a $600,000 fixed-price build against an $850,000 as-completed appraisal, the facility advances $108,000, $162,000, $135,000 and $135,000 across four draws — $540,000 in total — and keeps the last $60,000 until the lien period expires roughly 60 days after substantial performance. With prime at 4.70% since 29 October and the Bank of Canada policy rate at 2.50%, the interest on that drawn balance runs about $17,717 over a 14-month build. The number that decides whether your project finishes is not the rate. It is how much cash you can carry between the work and the draw.

That is the part of a construction mortgage nobody quotes you. The rate sheet on a construction mortgage is simple. The cash-flow mechanics are where self-builds fail.

What a construction mortgage actually advances

A progress-draw construction mortgage is sized on the as-completed appraised value of the finished home, not on what you have spent. Canadian lenders generally cap the facility at 75% of that as-completed value, and sometimes 80%. Land you already own counts toward your equity at its appraised value.

Take a worked example and hold it for the rest of this article. You own a serviced lot appraised at $250,000. You have a fixed-price contract with a licensed builder for $600,000. The as-completed appraisal comes in at $850,000.

• 75% of $850,000 is $637,500, so the cap is not your problem.
• Your facility is the $600,000 build cost, which is 70.59% of as-completed value.
• Your equity is the lot — $250,000, or 29.41% of the finished value.

On paper that is a comfortable file. Now watch what the construction mortgage actually pays out, and when.

The construction mortgage draw schedule, in dollars

A construction mortgage releases draws against the percentage of completion a lender's appraiser certifies on site, less the statutory holdback. Three to five draws is standard; four is typical for a custom build. The cumulative milestones below — foundation, lock-up, drywall and rough-ins, substantial performance — are the schedule most Canadian lenders use.

Draw	Certified complete	Gross entitlement	Advanced (less 10%)	Cost incurred	Cash gap
1 — Foundation and backfill	20%	$120,000	$108,000	$120,000	$12,000
2 — Lock-up	50%	$300,000	$162,000	$300,000	$30,000
3 — Drywall and rough-ins	75%	$450,000	$135,000	$450,000	$45,000
4 — Substantial performance	100%	$600,000	$135,000	$600,000	$60,000

Read the last column. The gap between what the build has cost and what the construction mortgage has released grows at every stage, and it is still $60,000 on the day you take occupancy. That is not a lender being difficult. It is the holdback, and it is law.

Note the second row as well. Between foundation and lock-up you complete 30% of the contract — $180,000 of work — and $162,000 arrives after the inspection, not before it. Somebody funds that stage first. On a fixed-price contract with a well-capitalised builder, the builder does. On an owner-build where you are paying trades and suppliers directly, you do.

The 10% holdback is $60,000 you carry past move-in

Every province requires 10% of each payment to a general contractor to be held back against construction liens. Your construction mortgage withholds the matching 10% from each advance, so the two holdbacks are designed to offset. The lien period runs roughly 45 to 60 days: Ontario's Construction Act gives 60 days from substantial performance, and British Columbia's is 55 days from the certificate of substantial completion.

Where this bites is timing, not arithmetic. The holdback on a $600,000 build is $60,000, and in practice it arrives about two months after the house is finished. If your builder expects to be made whole at occupancy, or if you are coordinating trades yourself, you need $60,000 of your own money standing in for it.

Bridging that with short-term money is expensive. At an illustrative 10.99% plus a 2% lender fee — an assumption for the purpose of this example, not a market quote — 60 days on $60,000 costs $1,084 of interest plus a $1,200 fee, or $2,284. Annualised, that is 23.16% on the money you borrowed. If you are weighing that route, read our breakdown of what bridge financing actually costs between closing dates before you commit, because the arithmetic is the same shape.

The appraisal gap: every point of certified completion is worth $6,000

This is the risk that sinks files, and it is almost never discussed when a construction mortgage is quoted to you. Your draw is not based on your invoices. It is based on the percentage the appraiser certifies. On a $600,000 facility, one percentage point of certified completion is $6,000 gross and $5,400 after the holdback.

You invoice at	Appraiser certifies	Net advanced	Cost incurred	Shortfall to fund
50%	50%	$270,000	$300,000	$30,000
50%	47%	$253,800	$300,000	$46,200
50%	45%	$243,000	$300,000	$57,000
50%	42%	$226,800	$300,000	$73,200

A five-point disagreement at lock-up turns a $30,000 float into a $57,000 one. Expensive materials sitting in a garage do not count as completion; installed work does. Deposits on cabinets, paid-for windows still on a truck, and site work outside the lender's budget all widen the gap.

Cost overruns work the same way and are harsher, because the construction mortgage amount is fixed at commitment. A 10% overrun on this build is $60,000, and the advance stays at $600,000, so the whole $60,000 is cash from you. Lenders generally want a contingency of 10% to 15% of hard costs for exactly this reason — $60,000 to $90,000 here — and a contingency you have not actually set aside is not a contingency.

What a construction mortgage costs in interest during the build

During the build a construction mortgage charges interest only, and only on the balance drawn. Construction facilities are priced above a standard mortgage; a common range is prime plus 1% to 2%, which at today's 4.70% prime is 5.70% to 6.70%. The table below uses 6.20% as an illustrative assumption — construction pricing is negotiated file by file and is not published, so treat it as a worked number rather than a quote.

Scenario	Rate	Interest cost
Draw structure, 12-month build plus 2-month holdback	6.20% illustrative	$17,717
Final month, on $540,000 drawn	6.20% illustrative	$2,790
Full $600,000 advanced on day one for 12 months	6.20% illustrative	$37,200

The draw structure is the one genuinely borrower-friendly feature of a construction mortgage: paying interest only on what has been advanced saves $19,484 against a single up-front advance. Budget that $17,717 of construction mortgage interest as a project cost. It is not in your builder's contract.

What you need to qualify, and the payment after conversion

At substantial performance the construction mortgage converts to a regular amortising mortgage, and you must qualify for that mortgage up front at the stress-tested rate — the greater of 5.25% and your contract rate plus two points. The best conventional five-year fixed on the market was 4.44% as of 30 October 2026, so the qualifying rate is 6.44%. All payments below are calculated on Canadian semi-annual compounding.

Rate	Term	25-year payment	30-year payment
4.44%	5-year fixed, conventional	$3,300.85	$3,004.38
3.65%	5-year variable, conventional	$3,043.32	$2,735.48
6.44%	Qualifying rate only	$3,997.15	$3,616.14

Add $433 of monthly property tax and $150 of heat to the qualifying payment and you are carrying $4,580 for debt-service purposes. With no other debts that implies household income of roughly $125,000 at a 44% total debt service ratio, or about $141,000 at 39%. The variable option is $257.53 a month cheaper today, but prime has already moved once this year and markets expect more movement around the 9 December decision — a market expectation that can change, not a forecast.

Lenders also want a credit score of 680 and often 700, a fixed-price contract from a builder with a valid provincial licence, permits, plans, a line-by-line budget, and new-home warranty enrolment or a documented owner-builder exemption. If your income is self-employed, the documentation burden is heavier again; our guide to qualifying for a mortgage when you are self-employed covers what lenders accept in place of T4s.

How to protect yourself before you sign a construction mortgage

1. Ask for the construction mortgage draw schedule in writing, with the certified-completion percentage attached to each draw, before you accept the commitment.
2. Confirm who orders and who pays for each draw inspection, and how many days pass between inspection and funding.
3. Get your builder's payment terms in writing and check them against the draw schedule. A builder who invoices on delivery and a lender who funds on certified completion is the mismatch you must fund.
4. Hold the holdback in cash, not in a plan. On this build that is $60,000 for roughly 60 days past substantial performance.
5. Fund a contingency of 10% to 15% of hard costs — $60,000 to $90,000 here — in an account you can actually draw on.
6. Have the as-completed appraisal reviewed before you firm up the build contract. The appraisal sets your ceiling, so a low one is cheaper to find out about early.
7. Price the construction-period interest into your project budget as a line item, not an afterthought.
8. Get the takeout mortgage pre-arranged, and ask whether the rate is held through the build or reset at conversion.
9. Keep every invoice, permit and inspection report. Draw disputes are won with documentation.

If your file will not support a bank construction mortgage — bruised credit, a complicated income picture, or a build the appraiser cannot value cleanly — alternative lenders will fund it, at a price. Our analysis of what a private mortgage actually costs in Canada sets out the fees and effective rates to expect before you go that route.

Common questions

Can I get a construction mortgage with less than 20% down?

Yes, on an insured progress-advance mortgage for an owner-occupied build, where the usual insured down-payment rules apply rather than the 20% to 25% a conventional construction mortgage wants. The trade-offs are the insurance premium, a lower price ceiling, and tighter rules on who may build. Most custom builds on an owned lot run conventional, because the lot equity already covers the requirement.

Do I pay the holdback, or does my lender?

Neither, exactly. You withhold 10% from payments to your general contractor, and your lender withholds the matching 10% from each advance, so the two are meant to cancel out. The problem is that the holdback is released only after the lien period ends, which means roughly $60,000 on a $600,000 build sits unavailable for about two months after the house is finished.

What happens if the build costs more than the appraisal supports?

The construction mortgage does not grow. The facility is set at commitment against the as-completed value, so an overrun is funded by you, by a second charge, or by stopping work. Lenders also enforce a balancing requirement: undrawn loan plus unspent equity must cover the remaining cost to complete, and draws stop until the gap is funded.

Figures in this article: Bank of Canada policy rate 2.50% and Bank Rate 2.75% as of 28 October 2026; prime 4.70% effective 29 October 2026; five-year Government of Canada benchmark yield 3.58% as of 29 October 2026; best conventional five-year fixed 4.44% and five-year variable 3.65% as of 30 October 2026; next scheduled Bank of Canada decision 9 December 2026. Construction-period pricing of 6.20% and the 10.99% bridge rate are illustrative assumptions, not market quotes. The lot value, build contract, appraisal and overrun scenarios are the worked example's parameters.