Roof Load

Roof live load is generally specified on the horizontal projection. The "projection" of a typical rafter spanning from an exterior wall to a ridge is the distance you walk along the floor from the outside wall until you're under the ridge. You can also think of it as the length of the shadow cast by a sloping rafter when the sun is directly overhead. Conversely, dead load is proportional to the sloped length. A steeper rafter over the same horizontal span will be a longer rafter, which, of course, weighs more. RedSpec� considers this, so the user should enter horizontal spans along with the roof slope. RedSpec� will do the rest. Please see Sloped Members for more information.