I haven't framed a roof in a long time, and started one last night but had one heck of a time figuring ridge height. It is a gable roof, 12" span, 6' run, 4/12 pitch. So i figure ridge height should be 24" . I cut a block 24" minus ridge with and place ridge on it a go to set rafters, too short. So i think maybe i have to add in the width of rafter, do that= too high. It was getting dark so i knicked out block and nailed it up with the rafters. I seem to remember there being a formula for figuring ridge height but cannot find it in any of my books. I seem to recall the birds mouth coming into play here. I do have the rafters cut right, so that isn't my problem. Any help would be appreciated, thanks guys.