In last month's column, we looked at the underlying logic of roof forms by examining the cross-section. This month, we'll look at the roof from the outside and see how various roofs join at the corners. The complicated roof forms that characterize many new houses are contrived to reproduce the visual effect of a popular style. But the essence of the style is often missed because the plan has to be tortured to fit under the preconceived roof. In other cases, the roofs look arbitrary because they are merely boxes of trusses set on the top of the building. If you remove the constraints required to design a roof over usable attic living space, you end up with