Erecting a Pole Building

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If you can't get factory trusses or would rather build your own, the next section is for you. Here we'll discuss how to lay out and build gambrel roof rafters and saddle roof rafters.

The saddle roof (see Fig. 23) is probably the most common roof today, and constructing its rafters is fairly simple.

The first thing to determine before laying out your rafters is what pitch you want your roof to have. Roof pitch is usually given in terms of height rise in the roof per foot; that is, a 4-12 roof pitch has a peak that rises 4" for every foot horizontally along the top plate to the middle of the building (Fig. 19). To ascertain the approximate length of 2 X 4 or 2 X 6 you'll need for your rafters, consult the rafter conversion table on your framing square, which, with a given pitch, will give you the length of the rafter. To this you should add any overhang you desire. This will give you the total length of the rafter.

The step-off method is used most frequently in laying out rafters, and entails the use of your framing square. Mark the ridge end of the rafter first, by laying your square with 12" on the blade and the unit of rise in the tongue both lining up on the edge of the rafter (Fig. 20). If the line length does not come to an even foot measurement, measure the smaller length from the top, then mark down the rafter a foot at a time until you get to the building line. At this point turn the square upside down, and mark out the overhang just as you have the rest of the rafter. To mark out the notch where the rafter sits on the plate, commonly called the bird's-mouth, run your square at a right angle to the building line about a third of the way up the line, and mark out the notch and the end of the overhang (Fig. 21). Use this piece as a pattern for the rest of your rafters.

To erect rafters of this type, mark out their locations on both sides of the ridgepole, and nail one side of each rafter to the pole. Set the ends of the rafters in place along the plate, and raise the ridge to its proper height with temporary 2 X 4 braces (Fig. 22). Now nail the rafters for the other side. Stud in the front and back peaks on 16" centers (Fig. 23).

The style of roof that many of us associate with barns is properly called a gambrel roof (see Fig. 24c). The reason for its popularity in barns is that it provides a large amount of storage area at a reasonable cost. Since a gambrel roof truss with its cross bracing would defeat this open space advantage, gambrel roof rafters are cut and erected on the site in the following manner.

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