Well in my opinion they are or there abouts, when considering the brick and block only make up the perimitter walls less openings, and when you consider the overall house construction you can consider tile battens, roof trusses, studding (maybe/maybe not) door frames, window boards, doors, skirtings, architraves, boxings, pattresses, internal thresholds, kitchens, 1st floor joists, perhaps even 2nd floor joists, floor boarding and so within a traditionally built house much is timber. So ill concede i cant hang my hat on exactly 50% and im not going to sit abd work it out and i dare say you cant either but my point stands that much of a traditional house is still flamable timber and to rubbish modern methods of construction based on that fact alone is just not forward thinking, and that is an actual Fact!