Measure from the point on the blade to the point on the tongueit must be 14-7/16 inches (cheap roofing). Multiply this by the run of the building. We're using 10 feet in this example, omitting the overhang. The resulting figure is 144-1/2 inches. We add 12 inches for the overhang to get a final figure of 156-1/2 inches.
Analyze the rafter board to identify if there is any curve or "crown" in the board. You need to make this very first pattern rafter on the straightest board you can find. If there is any curve in the board, lay out the rafter so the crown is up or dealing with away from you.
( If the crown were to be positioned down, the roof could eventually droop.) Then set out the rafter as shown on the next page. This example is for a roofing system with an 8/12 pitchPosition the square at the end of the rafter board, with the tongue on your left and facing far from you.
Mark along the behind of the tongue. This is the plumb cut for the roof ridge. Measure form the top of this line down the board to figure out the line length, or length of the rafter, less the ridge board. This commonly is a 2-by or 1-1/2- inch board, so the measurement is less inches.
Holding the square in the same position as in the past, discount to the side of the tongue. This marks the plumb cut at the within of the house wall for the notch (called a bird's mouth) to seat the rafter one the wall plate. Add the length of the overhang beyond this mark and mark it.
In the example shown this is 12 inches. Cut the rafter at the ridge line and at the overhang line. Then hold the square on the plumb line that marks the bird's mouth. Figure out the wall thickness or depth of the bird's mouth cut and make a mark - corrugated metal roofing. Cut the notch, initially with a handsaw or portable circular saw, and after that end up the cut with a handsaw.
Continue moving down the rafter and marking plumb cuts, including any odd figures. One technique of setting out rafters with a square is called "stepping off." Make a replicate rafter from the pattern. EPDM rubber roofing. Then lay the rafters out on a smooth, flat surface, with a 2-by in between them at the ridge line.
You may wish to check these on the structure before cutting the remainder of the rafters. As soon as you make sure these two pattern rafters are properly cut, mark them as patterns and mark and cut the required number of rafters. If the building has hanging or "fly" rafters for the gable ends, cut them as well.
Make certain you thoroughly follow the pattern rafter. A number of years ago I was constructing a two-story building. One carpenter set out and began to cut the rafters. He ended up being ill from the extreme heat of the day and another carpenter took control of for the last 3rd of the rafters.
I do not understand if the 2nd carpenter didn't use the pattern rafter, or just wasn't as exact, but it was a costly error. The brand-new C.H. Hanson Pivot Square makes the chore of laying out a roof rather simple. I wish I had this tool a number of years and buildings ago.
It comes with its own durable belt holder that is likewise created to hold a carpenter's pencil and the instruction booklet. The brand-new C.H. Hanson Pivot Square makes it eady to lay out rafters. this quality tool includes its own belt pouch and has dividers for the square, an instruciton manual and a carpenter's pencil.
Degrees and rise are marked on a blade connected to the pivoting arm. With the common rise figures facing you, and the raised fence on the right, the bottom represents the base of the triangle (the run) and the ideal side the altitude (the increase). The long adjustable edge represents the hypotenuse of the triangle, or the line length.
Just adjust the square to the preferred pitch and lock in location with the knurled knob. You can then use the square to transfer the angle for the cut to the lumber. Or you can hold the square in location and use it as a sturdy guide for running a portable circular saw.
Identify the pitch, then you can set a miter saw or compound miter saw to make cuts in degrees that comply with the preferred pitch. The Pivot Square can also be used to set out pitches steeper than 12/12, as well as to lay out hip-valley rafters. These figures are determined on the rear end of the square.