The client
A household self-building in New Glasgow, Nova Scotia on a $320,000 committed construction budget, with combined income of $8,400/month. While the build was underway, they kept paying $1,700/month rent on their current home — a routine arrangement for a self-build, and the one that turned out to matter most.
Construction budget
$320,000, fully drawn by completion
Uninsured; land already owned
Current rent, during the build
$1,700/month
Ends once the build is occupiable
Combined income
$8,400/month
Both employed
Other debt
$300/mo car loan
the only item on the bureau
The problem
A construction loan charges interest-only on funds actually drawn, not on the eventual completed amount — a payment that rises with every draw and peaks right before the final one, at the loan's full committed size.
What the household was carrying at peak draw
- ▸Interest-only payment on the fully-drawn $320,000 construction loan: $1,720/mo
- ▸Rent on their current home, still being paid: $1,700/mo
- ▸TDS on both together: 44.3% — over the 44% comfort ceiling, in the weeks just before completion
The household's own plan had focused entirely on whether the eventual, completed mortgage would be affordable. It was — the risk this file actually ran into was narrower and shorter-lived: the overlap between rent still owed and the construction loan's peak carrying cost, in the exact weeks before the build was finished.
The numbers
Two different mortgages exist in this file at two different times, and only one of them was ever close to a problem.
| Interim carrying cost vs. the completed mortgage | Amount |
|---|---|
| Construction budget, fully drawn | $320,000 |
| Interest-only rate during construction | 6.45% |
| Peak interest-only payment | $1,720/mo |
| Contract rate on the permanent mortgage at completion | 5.15% |
| Minimum qualifying rate (greater of contract + 2% or 5.25%) | 7.15% |
| Qualifying payment on the completed mortgage, 25 years | $2,271/mo |
| TDS comparison | During the build (rent + peak IO) | After completion (amortizing, no rent) |
|---|---|---|
| Housing cost | $1,700 rent + $1,720 IO | $2,271 qualifying payment + $360 tax/heat |
| Car loan | $300 | $300 |
| TDS ÷ $8,400 income | 44.3% ✗ | 34.9% ✓ |
The completed mortgage, stress-tested at 7.15%, leaves real room — 34.9% is well inside the 44% comfort ceiling. The tighter constraint, briefly, was the overlap: paying both the rent on the old home and the peak interest-only cost of the new one at the same time, in the weeks before the build closed out.
The solution
A mortgage broker working under Nova Scotia's licensing framework identified the interim overlap as the actual constraint, not the completed mortgage.
First, modelled the carrying cost at every draw, not just at completion — showing the peak interest-only payment landed right when the household was also carrying a full month's rent, the single tightest point in the whole progress-advance process.
Second, coordinated an early move-in. Once the home was substantially complete and the municipality had signed off on occupancy, the household moved in ahead of the final inspection and draw — a common step that ends the rent overlap without requiring the build to be fully finished first.
Third, timed the last draw and inspection around the household already living there, rather than around a rent payment that no longer needed to run in parallel.
The outcome
With the rent gone, TDS on the peak interim payment fell to 24.0%, and the final draw released without the file needing to be re-argued. The completed, amortizing mortgage funded afterward at 34.9% TDS, exactly as modelled from the start.
This mortgage is uninsured; the 44% figure used throughout as a comfort reference is a lender convention for a construction-phase carrying cost, not a CMHC-tested ratio.
What to take from this file
- 01The completed mortgage and the interim carrying cost are two different affordability tests. A file can pass one comfortably and fail the other, briefly, at exactly the wrong moment.
- 02Model every draw stage, not just the final number. The peak interest-only payment, not the eventual amortizing one, was the real constraint here.
- 03An early, permitted move-in can end a rent overlap before the build is fully finished. It doesn't require the final draw to have happened yet — just an occupancy sign-off.
- 04Interest-only payments rise with every draw. A household budgeting off an early-stage number will be surprised by what the loan actually costs once it's fully drawn.
- 05A self-build's real risk window is often narrow. This file's tightest point lasted only a few weeks — but it was the point that mattered.
Sources
Every regulatory figure in this file traces to one of these primary sources. Client details and anything that varies by lender are illustrative, as flagged below.
- ▸OSFI — Minimum qualifying rate for uninsured mortgages — the minimum qualifying rate — greater of contract rate + 2% or 5.25%.
- ▸CMHC — CMHC Reviews Underwriting Criteria — GDS 39% / TDS 44% maximums and the 600 credit-score floor for insured files.
- ▸Provincial/territorial mortgage-broker legislation fetched directly (bclaws.gov.bc.ca, legisquebec.gouv.qc.ca, fcaa.gov.sk.ca, web2.gov.mb.ca, nslegislature.ca, assembly.nl.ca) plus FCNB's own site for NB and CanLII's index for PE — see notes for per-province method — provincial mortgage regulators and licence titles.
Illustrative in this file — lender-specific, not rules:
- ▸6.45% interim interest-only rate / 5.15% completion contract rate — rates move daily; neither is a quote.
- ▸the 44% comfort reference during construction — a construction-phase interim payment is not itself a CMHC-tested ratio; this mortgage is uninsured, and the number is a lender comfort convention.
Authority & provenance
How this case file was built
We publish the origin, the verification method and the reviewer for every case file, so you can judge how far to trust it before you rely on it with a client.
Where it comes from
Derived from files handled by Treadstone’s fulfillment desk and from scenarios contributed by partner brokerages. Names, employers, exact amounts and dates are changed so no client or file is identifiable.
Provenance: Composite — a pattern seen repeatedly on fulfilled files, not a single transaction.
What is verified
Every regulatory figure traces to a primary source listed above and was checked against it on the date shown. The arithmetic is recomputed by machine on every rebuild.
Anything that varies by lender is labelled illustrative rather than stated as a rule.
Who reviewed it
Reviewed for Canadian regulatory accuracy before publication, and re-checked whenever a cited rule changes.
Reviewed by: Nicholas Parson, Treadstone Associates — reviews every case file before publication.
This case file is professional reference material for licensed mortgage professionals. It is not advice to a borrower, and it is not a lender commitment. Insurer rules, qualifying rates and provincial taxes change — confirm the current position with the insurer, regulator or lender before you rely on any figure here in a live file.