Ask the designer
We are in the planning stage of a major renovating and extending our 2 level home built in the 1970’s. Will the roof trusses need to be replaced or only the roof sheeting if adding major sections to existing roof?
It is possible to retain the existing roof depending on the scale of work being done which may save on cost. However it is best to consult your builder/ structural engineer about the feasibility of retaining the existing roof. Also consult them about both options before making and big decision especially in relation to structural issues.