Most homes built before the 1960s are traditional framed where everything was made and cut to size on the site. This is the easiest kind of roof for a loft conversion as the space can be opened up easily with the rafters strengthened and adding support. For those built post 1960s, most of the roofs are known as truss sections where the roof was easier to put up and made of lighter material. The truss sections tend to have no load bearing structure therefore when you convert your loft you will need to add in supporting steel beams. This option will cost more and will take more time.