In Renovation mode, building objects are automatically categorized as Existing, Demolition, or New. Objects interact based on their Renovation category. For example, objects categorized as Existing and New interact with each other, but objects categorized as Demolition and New objects do not. Therefore, if you have walls that are categorized as Demolition and walls that are categorized as New, and you want to have them intersect, you can modify them manually.