#Rafter length table free#

If you follow this line over to the column headed by the figure 8 (for a unit of rise of 8), you will find the figure 10 7/8. Already having the rise will make it easy to determine the rafter length by loading the numbers into the equation chart.

(Look ahead to figure 2-41.) You will see that the bottom line in the table is headed SIDE CUT HIP OR VALLEY USE. FT IN TOP PLUMB CUT LINE ) Subtract / of the.

#Rafter length table free#

The angle of the side cut on a hip rafter may also be laid out by referring to the unit length rafter table on the framing square. Find the rafter length from Table (as feet, inches), and lay out and mark this length on the measuring line. Online Rafter Length Calculator Calculate the length of common rafters with this free and easy online tool by entering a dimension for the roof width, selecting a pitch for the roof, and the thickness of the ridge. All we do now is use a calculator to multiply 1.610 by the measurement in the book: 1.1543 x 1.610 1.858m So, the rafter lengths 1. This means that for every 1m the rafter travels horizontally, the angled length of the roof will be 1.1543m. The tail of the rafter must have a double side cut at the same angle, but in the reverse direction. The length of rafter per meter of run is 1.1543. For one to be framed against the ridge ends of the common rafters, there will be a double side cut, as shown in the figure. For a hip rafter to be framed against the ridge, there will be only a single side cut, as indicated by the dotted line in the figure. Then, turn the rafter edge-up, draw an edge centerline, and draw in the angle of the side cut, as indicated in the lower view of figure 2-33. Shift the tongue to the mark, set the square to the cut of the rafter (17 inches and 8 inches), and draw the plumb line marked ∺ in the figure. the ridge cut line, as shown, and measure off one-half the thickness of the hip rafter along the blade. Place the tongue of the framing square along Figure 2-33.Laying out hip rafter side cut. The angle of the side cut is laid out as shown in figure 2-33. The angle of the side cut is more acute for a high rise than it is for a low one. A hip rafter, however, joins the ridge, or the ridge ends of the common rafter, at other than a 90° angle, and the ridge end of a hip rafter must therefore be cut to a corresponding angle, called a side cut. Rafter Side Cuts Since a common rafter runs at 90° to the ridge, the ridge end of a common rafter is cut square, or at 90° to the lengthwise line of the rafter.

Set the unit of rise, whatever it might be, on the tongue even with the same rafter edge. When stepping off the length of the overhang, set the 17-inch mark on the blade of the square even with the edge of the rafter.

The overhang may also be stepped off as described earlier for a common rafter. Add this product to the theoretical rafter length. Multiply the bridge measure (in inches) of the hip or valley rafter by the projection (in feet) of the common rafter overhang: 3. Find the bridge measure of the hip or valley rafter on the framing square (refer to figure 2-16). 18 inches for a roof with an 8-inch unit of rise, the length of the hip or valley rafter tail is figured as follows: 1. If you want to add on a rafter foot (overhang) add this to your rafter length. Multiply this factor by your run which gives your rafter length. Just multiply the rise or run by the appropriate rafter length factor corresponding to your roof pitch.įor example, if your roof pitch is 30ﹾ and your run is 2.4m then reading from the table the rafter length factor is 1.15. There is a useful table below for your convenience. Rafter length = 2.4 ÷ cos(45°) = 3.39m to 2 d.p.Īny modern mobile phone will be able to perform these calculations. Rafter length = Run ÷ cos θ = Rise ÷ sin θįor example. Using a bit of trigonometry you can find the rafter length using the following equations. Method 2 – You know the roof pitch, θ, and the rise or the run. The eagle-eyed will have spoted this is another example of a 3-4-5 triangle.