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What Is Missing Middle Housing in Ottawa?
Missing middle housing in Ottawa means the mid-density building types between a detached house and an apartment tower — duplexes, triplexes, fourplexes, small multiplexes, and low-rise apartments. The catch: the word has two meanings in this city, and they don't match.
Two Definitions That Collide
The builder's definition: 2–6 units
On the ground, "missing middle" usually means a small multiplex — a duplex, triplex, fourplex, or sixplex on a single residential lot. This is the version that matters for the as-of-right rules in Ottawa Zoning By-law 2026-50.
The City's definition: ~8–16 units
In its planning documents, the City of Ottawa has used "missing middle" to mean larger multi-unit buildings of roughly 8 to 16 units — the scale that has historically been hard to build as-of-right and needed rezoning.
This hub uses the broad definition: every type between a house and a tower. When a unit count matters for the rules, we say it plainly — three under Bill 23, four under By-law 2026-50, more in the higher N-zones.
The Building Types
Duplex
Two units, side-by-side or stacked. The smallest missing middle form and the easiest to add to an existing Ottawa house.
Triplex
Three units. Sits exactly at Ontario's Bill 23 as-of-right floor — buildable on most lots without a rezoning.
Fourplex
Four units. The workhorse of Ottawa's as-of-right era under By-law 2026-50, which allows four units on a serviced lot.
Small multiplex (5–6)
Five or six units in one building, allowed in the higher N2 Neighbourhood zone. The point where the multiplex starts to behave like a small apartment.
Low-rise apartment (up to ~10)
Permitted in N3. Closer to the City of Ottawa's own 8-to-16-unit definition of missing middle.
Townhouse / stacked row
Ground-oriented units in a row. A missing middle form when it fills a single lot rather than a large subdivision.
Where the Term Came From
Daniel Parolek of Opticos Design coined "missing middle housing" in 2010 to name the building types that mid-20th-century North American zoning had quietly outlawed — the duplexes, fourplexes, and courtyard apartments that used to fill the gap between single houses and big apartment blocks. Ottawa's Zoning By-law 2026-50 is, in effect, the City re-legalizing that middle.
Best For
- ✓ Understanding the full range of building types the word "missing middle" covers in Ottawa.
- ✓ Telling the difference between a small multiplex and the City's larger 8-to-16-unit definition.
- ✓ Getting oriented before reading the policy and zoning pages.
Usually Fails When
- ✕ You need the exact unit count your lot allows — that depends on your N-zone, covered on the zoning pages.
- ✕ You want construction costs — this page is about definitions, not budgets.
What To Verify Before Spending Money
- → Which definition a given document is using before you compare unit counts.
- → Your lot's Neighbourhood zone on geoOttawa to see which building types are in play.
Frequently Asked Questions
What is missing middle housing in Ottawa?
Why are there two definitions of missing middle in Ottawa?
Is a fourplex missing middle housing?
Is missing middle the same as a multiplex?
Official Sources Referenced
Coming to Ottawa
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