Hello all, my partner and I are building a timber frame home up here in Northern BC and want to include a dormer. For the challenge we want to design, engineer and build a timber dormer. In the Guilds Timber Frame Joinery and Design Workbook, Ed Levins drawing of a similar style dormer has the jackrafters joining the side of the valley rafter instead of the top (plane of the roof). This seems to make the joinery more complicated and yet I am unable to see the design advantage? Is it stronger, more aesthetically pleasing, or just a technical challenge. The associated article was good in explaining the Hawkindale angles and how to approach the drawing of compound angles but it fails to answer the why's of joinery. As these are Ed's drawings I am sure there is a 'why' and I am just missing it. What am I missing?
Thanks