Does a seller have to tell me if a home was previously used as a marijuana grow operation?

Ontario law generally splits defects into two categories: patent defects, which a reasonably careful inspection would reveal, and latent defects, which are hidden and which a seller who knows about them must disclose if they make the home dangerous or unfit to live in. A former grow operation can leave latent problems behind, including electrical alterations, mould from excess humidity, and structural changes to support lighting and ventilation, so a seller who knows the history and knows it created a condition affecting safety or habitability generally cannot stay silent about it.

That said, there is no standalone rule requiring a seller to announce a property's history as a former grow-op simply because it happened; the duty is tied to whether known physical conditions make the home unsafe or uninhabitable, not to the stigma of the label itself. A seller who is asked directly and answers falsely takes on real risk. Buyers concerned about this history should ask direct questions in writing, request any available municipal or insurance records, and have an inspector specifically check electrical work, ventilation modifications, and moisture damage before waiving any conditions.