Ontario Regulation 462/24 sets selected provincial site standards for additional residential units (ARUs) on qualifying urban residential land. Its unit and parcel conditions matter: the regulation covers specified second or third units in detached, semi-detached, or row houses, and units in ancillary buildings when the stated residential-use and unit-count tests are met. It does not establish that a unit is permitted on a particular property.

The provincial coverage and separation baseline

For the covered configurations, the regulation allows buildings and structures to cover up to 45% of the parcel surface. A municipal zoning by-law that permits more coverage prevails. It also sets a 4 m separation from another building or structure that contains a residential unit, but a municipal by-law that permits a shorter separation prevails.

The listed provincial standard sets no floor-space-index limit. That does not mean a project has no size or location limits: municipal maximum-height and minimum-setback rules remain relevant, as do the regulation’s own eligibility conditions. Floor-space index compares the total floor area of buildings and structures with parcel area, so the correct definitions and calculation inputs still matter.

Confirm the local rule before measuring

First establish whether the parcel and proposed unit configuration qualify under the current regulation. Then check the municipality’s zoning by-law for any different coverage or separation rule, and confirm local setbacks, height, definitions, and measurement methods. Do not combine the provincial figures with Toronto, Ottawa, or another municipality’s distinct local standards.

These are zoning form rules; they do not establish fire separation, emergency access, structural safety, servicing, or permit approval. The official regulation is the controlling source, while local zoning and parcel facts determine how its standards apply. If the urban-land status, unit count, municipal override, or measurement is unclear, obtain confirmation from the municipality before using a design envelope.