What Markham publishes for additional units
Markham’s building-permit guide has a dedicated Additional Residential Units / Secondary Suite application stream. The city publishes a homeowner guide covering whether a suite is allowed, how to obtain the permit and how the unit is registered.
Open the official Markham suite source ↗Housing changes elsewhere in Greater Toronto Area do not establish permission on this parcel. Use the Markham zoning and permit route for the local answer.
Ontario: the provincial layer
Ontario’s province-wide additional-unit rules create broad permission on identified residential lands, including three units in a primary house or a two-plus-one main/ancillary configuration. Local setbacks, height and site standards continue to matter.
Ontario additional residential unit framework ↗Before drawings: four approval questions
What kind of unit?
An internal conversion and a new detached unit can share a goal but not an approval path.
Is the use allowed?
A general right to additional housing can still come with lot-specific limits. Check the address before treating the project as permitted.
Can the building comply?
Life-safety and building-system requirements can be the hardest part of legalizing an older unit, so investigate them before cosmetic work.
Can the site serve it?
A permitted use can still be difficult to build if the lot cannot satisfy servicing, access or site-layout requirements.
For a Markham property, check permission before construction
A good sequence is property eligibility, unit type, building design, utilities/trades and inspections. Starting with finishes can hide the expensive constraints.
For an existing unit, request the municipal permit history and any final inspection or occupancy record. Present use alone does not prove approval.
Official sources
Reviewed 2026-09-14. The city-specific housing source is only one layer; provincial code and the property’s current approvals still need to be checked before construction.