Generally, the HST at 13% applies to a taxable sale by a builder of newly constructed or substantially renovated housing in Ontario where, under the written agreement of purchase and sale, both ownership and possession of the housing transfer to the purchaser on or after July 1, 2010. However, the provincial part of the HST does not apply to a grandparented sale.
https://www.canada.ca/en/revenue-agency/services/forms-publications/publications/rc4022/general-information-gst-hst-registrants.html#H3_372
https://www.canada.ca/en/revenue-agency/services/forms-publications/publications/rc4022/general-information-gst-hst-registrants.html#H3_372