Ottawa's four-unit rule is a ratio. N1 needs 500 square metres

Nobody quotes the number that actually decides it

Every fourplex pitch in this city runs on one sentence. Four units on any serviced residential lot, as of right, thanks to the new zoning by-law.

So go and read the row. Table 801A of Zoning By-law 2026-50, row (i), maximum number of dwelling units, N1 column:

0.8 per 100 square metres of lot area, maximum 4 per building.

That is a density ratio with a ceiling bolted on. The ceiling is the part everyone repeats. The ratio is the part that decides whether your deal exists, and I have never heard it quoted at a showing.

Run it backwards and it gets uncomfortable

In N1 the arithmetic is fixed. Four units needs 500 square metres of lot area. Three needs 375. Two needs 250. There is no partial unit, so you either clear the threshold or you do not.

Five hundred square metres is 5,382 square feet. On a lot 100 feet deep, that is close to 54 feet of frontage.

Hold that against the lots people are actually pitching. A 30 by 100 foot lot is 279 square metres, which is two units. A 40 by 100 is 372 square metres, which is also two units, because three needs 375. That lot misses the third unit by three and a half square metres. At 100 feet of depth, that is about four and a half inches of frontage.

A 50 by 100 gets you three. The fourth does not appear until roughly 54 feet wide, and lots that wide in the N1 parts of the city are not the ones being marketed as fourplex plays.

Check which letter you are in before anything else

N1 is the tight one. N2 runs 1.5 units per 100 square metres to a maximum of six per building. N3 runs 2.5 per 100 to a maximum of twelve.

Same 40 by 100 lot. N1 gives two units. N2 gives five. N3 gives nine. Same dirt, same frontage, three different businesses.

I pulled all 14,834 zoning polygons in the by-law to see how the land splits. Of the area sitting in N1 through N6, N1 holds about 21 per cent, N2 about 26 and N3 about 39. N4, N5 and N6 together are under 14 per cent, and the unit row reads n/a for all three, so what caps those sites is height and the rest of the table rather than a ratio.

That is land area, not a lot count, but the shape of it is clear. A fifth of Ottawa's neighbourhood-zoned land sits under the 0.8 ratio, and that fifth is where most of the older, narrower lots are. This is the same 2026 rewrite that renamed every zone in the city.

The row is still under appeal, and now you can see it

The City has finished flagging the appealed text. Provisions not in force are printed in bold italic with the tribunal file number attached.

Row (i) of Table 801A is italic across all six columns, tagged OLT-26-000364, issue date July 2, 2026. Row (ii), maximum building height, is not italic. Heights are in force. The unit count is not.

Section 801(5) is out. So is 801(6), the unserviced version: no more than two units on a lot without municipal water and sewer, a coach house counts toward the two, and the minimum lot area is whatever existed on March 11, 2026. Parts of 801(7) covering building depth and vertically attached units are out as well.

I wrote in July that the unit-count provisions were the ones stuck at the tribunal. Two months on they are still stuck. What changed is that you can now read the exact words instead of cross-referencing a memo.

What you can build this morning

Until the appeal resolves, an application deemed complete on or after March 11, 2026 has to satisfy both the old by-law and the new one, with the more restrictive provision winning.

The City's building permit page puts it in one line: where permitted, the number of dwelling units on a lot, including the principal unit, must not exceed three total units.

Three. A principal unit plus two more, either as two apartments inside the building or one apartment plus a coach house on the lot. The two-unit version of that math is the one piece of this library that reliably moves a house toward carrying itself.

The map carries an asterisk too

Site-specific appeals show on the zoning map as an asterisk prefix on the zone code. I pulled that layer. It holds 381 polygons, 342 of them carrying the OLT-26-000364 file and a July 2 date.

Before you count those as 381 contested sites, 291 of them carry an internal note tying them to a 30 or 300 metre VIA rail corridor buffer, so most of that number is corridor geometry cut into pieces rather than separate fights. Around 90 sit elsewhere, and those do include individual N1 and N3 sites with their own exception numbers. If your target address shows an asterisk, the zone itself is contested and nobody can tell you when that ends.

How I would underwrite it

Ask for lot area in square metres. Not frontage, not the listing's rounded lot size, the area. Then divide by 125 in N1, by 67 in N2, by 40 in N3, and take the whole number. That is your unit count if the appeal lands where the City wants it.

Underwrite three. Three is available today, it is provincially backed, and if a fourth arrives later it is upside you did not pay for. Paying a density premium for a ratio that is not in force, on a lot that may not clear the threshold anyway, is two bets stacked on one purchase.

The money has not softened to cover that. The Bank of Canada held at 2.25 per cent on September 2, its seventh consecutive hold, and flagged higher upside risk to inflation from energy prices and tariffs. The next decision is October 28. A deal that only works after a cut is still not a deal, and the hurdle the rent has to clear has not moved either.

If you are looking at a lot with a multi-unit story attached, send me the address before you write anything. I will pull the zone, the lot area and the appeal status and tell you what the arithmetic actually permits. 613-262-6545 or fil@613realtor.ca. Or see what is listed right now.