I love cut roofs! They are a true testament to the skill and craftmanship of carpenters.
Don't get me wrong, I think trusses are pretty much always more efficient in terms of construction timing and cost but there's just something about cut roofs that really demonstrates the carpenter/builder knows their stuff. Sadly, very few homes today are built with cut roofs.
So what is a cut roof? It is timber beams, purlins and struts that are all cut and nailed together on site. The carpenters construct the internal walls of the home then support the roof structure off it - in an elaborate and skilled toothpick style!
Truss roofs are much more common today, as the typically triangular shaped trusses are manufactured in a factory, brought to site and can be erected quickly and easily. Because of the engineered nature of trusses, they are structural and can span from one external wall of the home to the other.
What is my roof? The easiest way to tell if your existing roof is a truss or cut construction is to look at the joins. Are there shiny galvanised nailing plates joining everything together? Then it's a truss. If not, then it's more than likely been cut. Cut roofs also always seem to have a more spacious cavity, there's a lot less timber, making for a perfect attic.
What does this mean for you? Well, it comes down to where your loadbearing walls are located. A truss roof pretty much always spans between the external walls, i.e only the external walls are load bearing. But a cut roof can rely on props and struts transferring loads down to your internal walls. So knowing what your roof construction is before you start planning your renovation is essential to save you an expensive surprise (or a saggy roof).
There are also many other types of roof construction - but your typical suburban 60's or 70's home with a tile roof and a flat ceiling is likely to be one of the above.