What records explain additional residential units at a Halton Hills home?

The Town's page says Official Plan Amendment 58 and the matching zoning amendment took effect on December 9, 2024. Its information sheet for urban residential zones, from By-law amendment 2024-0098, says an additional residential unit is permitted within, or in a building detached from, a single-detached, semi-detached or townhouse dwelling, and a lot may have two: both inside the main building, together using no more than 60% of its floor area or 220 square metres, or one inside (up to 40% or 110 square metres) and one detached (up to 40% or 90 square metres), whichever is less in each case; a unit entirely in the basement may take the whole basement. The main home needs two parking spaces and each unit one. Rural zones have their own information sheet.

Under By-law 2023-0060 no one may operate or permit the occupancy of an additional unit unless it is registered with the Town; registration follows the building permit and the Town's inspections, and the Town's guide says registration legalizes the unit's existence. A general permission does not make an existing basement apartment lawful; registration, the building permit and inspections are the records that do.

• Additional Residential Units: the Town's page on where units are permitted, the steps and By-law 2023-0060
• ARU information sheet: urban residential zones: the zoning standards from By-law amendment 2024-0098, August 2025 (PDF)
• ARU Registration Guide: the Town's guide to registering a unit under By-law 2023-0060, updated 2025 (PDF)

Extra units allowed is in the free check as a summary of the Town's rule, from our hand-kept table of city rules, and the full report reads the lot's zone where the Town's zoning map is open data we can use; where it isn't, the report's line says where the Town publishes it. Neither is confirmation that a particular unit holds a permit or may be occupied.

Free check: pick “Extra units allowed” See the sample report