Old Ottawa South has two markets. Carleton splits them.

Lease turnover in the southern half of Old Ottawa South is five days away. September 1 is the date the entire student rental model runs on, and this is the first year in a while I would treat that date as a test rather than a formality.

The neighbourhood guide I published in May got something right and then underplayed it. Old Ottawa South is not one housing market. It is two. The line runs roughly along the Carleton approach at the south end, and the two halves are moving in opposite directions right now for reasons that have nothing to do with the neighbourhood.

CMHC put the split in writing

In the 2026 Mid-Year Rental Market Update, released June 9, CMHC reported that vacancies were highest in two segments: structures built after 2020, and units located near post-secondary institutions. In the same breath it said older stabilized buildings and family-sized units continue to see tighter conditions.

Read that twice, because Old Ottawa South contains both of those segments inside a fifteen minute walk of each other.

Ottawa's overall apartment vacancy rate was 3.0% in 2025. CMHC's own estimate of a balanced range for this market is 2.0% to 4.0%, so the headline number says Ottawa is sitting comfortably in the middle of normal. That average is hiding a lot. Asking rents here have been falling since Q2 2025. On CMHC's index the two-bedroom asking rent peaked at 108.7 in Q1 2025 and was down to 104.4 by Q4, roughly a 4% give-back. Ottawa was the last of the big Canadian markets to roll over. It rolled over anyway. I went through the citywide version of this in the post on the softening rental market. This is the neighbourhood-level version.

Carleton's own budget is the demand signal

On June 16 the Provost told the Carleton community that the 2026-27 operating budget had been approved with a combined deficit of about $32 million. The letter names the cause directly: constrained tuition policy, rising fixed costs, and enrolment volatility driven primarily among international students since the federal restrictions came in. One of the four stated budget priorities is enrolment recovery.

A university does not list enrolment recovery as a priority when enrolment is fine.

Then look at what is scheduled. IRCC's 2026-2028 Levels Plan sets new international student arrivals at 155,000 for 2026 and 150,000 for each of 2027 and 2028, as part of a commitment to bring the temporary resident population below 5% of the national total by the end of 2027. Those are targets, not forecasts, and they run for three more years.

I am not predicting Carleton empties out. Domestic enrolment is the bulk of it. What I am saying is that the marginal tenant in the southern pocket, the fourth or fifth bedroom in a converted house, is the one most likely to have been an international student, and that student's arrival is capped by federal policy through 2028.

One empty bedroom does more damage than people think

In my cap rate breakdown I used a worked example for a Carleton-adjacent house: $780,000 purchase, four bedrooms at $1,000 a month, $48,000 gross, and after utilities, tax, insurance, a maintenance reserve and a 12% vacancy and management allowance, net operating income of $23,140. That is a 2.97% unleveraged cap rate.

Hold every one of those assumptions and empty a single bedroom for the year:

• Four rooms let. Gross $48,000, NOI $23,140, cap rate 2.97%.
• One room unlet September to April. Gross $40,000, NOI about $16,100, cap rate 2.06%.
• One room unlet all twelve months. Gross $36,000, NOI about $12,580, cap rate 1.61%.

One empty bedroom takes roughly 46% of the net operating income off that property. The 12% vacancy allowance sounds generous until you notice that one room out of four sitting idle is a 25% revenue loss, which is more than double the cushion. Per-room rentals do not degrade gracefully. They fall in quarter-steps.

That is the part the spreadsheet never shows. I covered the operating and by-law side of this model in the student rental post in July, and I stand by all of it. What that post assumed, and what I am now questioning, is that the tenant shows up.

The north end is on the other side of the same trade

Most of the neighbourhood is not in the southern pocket at all, and CMHC's finding was two-sided. The segment getting tighter is older stabilized stock and family-sized units. That is a precise description of the Hopewell catchment: century detached, three and four bedrooms, one household per house, no exposure to student demand whatsoever.

So the north half of Old Ottawa South is sitting in the tightening segment while the south end sits in the loosening one. Same postal walk, opposite directions.

What I would actually do about it this fall

If you are buying a family home here. The investor bid on converted houses in the southern pocket is weaker this year than last. That is your opening. A de-conversion, taking a chopped-up four bedroom back to a single household, competes against fewer buyers in the fall of 2026 than it did in 2024. Budget properly for it, because putting a house back together is not cosmetic work, and read the rental history before you write.

If you are buying that house as a rental. Underwrite three rooms let, not four. If the deal only works at full occupancy, it is not a deal, it is a bet on the federal immigration levels plan being revised upward. Ask the seller for the actual lease dates and the actual vacancy history over the last two Septembers rather than the pro forma.

If you are selling in the southern pocket. Get it leased before you list, or price it as a house rather than as a business. A buyer paying for a rental income stream will discount an unlet room far harder than a family buyer will discount a dated kitchen. If you sell it as a house, you reach the larger of the two buyer pools.

If you own in the Hopewell catchment. None of this is your problem. Your half of the neighbourhood is in the segment CMHC says is getting tighter, and the Glebe side has its own separate story that I covered in the Lansdowne construction post last week.

The reason to care about any of this on August 26 is timing. September 1 tells you which half of Old Ottawa South you are actually in, and it tells you before the fall listings hit.

If you own a converted house south of Brewer and you want a straight read on whether to lease it, sell it, or put it back together, call me at 613-262-6545 or email fil@613realtor.ca. Bring the lease dates. That conversation is worth more than another market report. You can also browse what is listed in the area if you want to see the inventory first.