CRA states that substantially renovating the personal-use portion of a rental property (without changing floor areas) generally would not engage the change-of-use rules
CRA considers a real estate property that has not been partitioned to be a single property. Thus, for example, if a duplex containing two identical units with unit 1 used for personal purposes and unit 2 being rented out, has a reversal of use, so that unit 1 starts to be rented out and unit 2 to be used for personal purposes, the change of use rules would not apply, because the rental-property use of this single property stays at 50%. When asked what would happen if unit 2 then was substantially renovated so that its relative value increased, CRA stated that this:
would not in itself have the effect of changing the relation between the use regularly made by the taxpayer of the property for gaining or producing income and the use regularly made of the property for other purposes. Our comments would be different if the renovation had the effect of changing the relative area of each unit.
Neal Armstrong. Summaries of 2 February 2017 Quebec CPA Individual Taxation Roundtable, Q.1.4, 2016-0674831C6 Tr under s. 45(1)(c) and s. 4(1)(a).