DIY Frame Rafter Building for Barn Storage

Gable

• 1

  Design a gable barn roof based on the width and height needed to provide storage space. Use those dimensions to calculate a pitch or slope for the two sides. A steep pitch, such as one that rises 12 inches for every foot between the wall and the peak -- a 12/12 pitch -- will provide more internal space. Use a lower pitch with a wider roof. A 7-inch pitch on a wider roof might provide adequate space.

• 2

  Cut gable rafters to the pitch angle, using a speed square. Put the pivot point of the square at the top of a rafter board and align the "common top cut" line -- 7 for a 7/12 roof -- on the square with the edge of the board to form an angle for the top or peak of the rafter. Calculate the length from peak to wall, add an overhang as desired and mark the other end of the rafter to the reverse of the top cut angle.

• 3

  Brace gable rafters with a cross tie horizontally about one-third of a way below the peak and two vertical supports on either end of that connect to the underlying joist. Add angled braces on each side, from the bottom of the vertical brace to the rafter and vertically between that point and the joist below. These should form three triangles within the larger triangle of the joist, rafter and vertical brace.

Gambrel

• 4

  Build gambrel rafters with reverse pitches, such as a 7/12, rising 7 inches per foot, for the top rafter slope and 12/7, falling 12 inches in every 7, for the bottom slope rafter. Use the square to mark gambrel rafters. Align the 7 at the top and bottom of the first rafter to make those angles and the 12 for those cuts on the second rafter.

• 5

  Cut the rafters to the length so each rafter will cover approximately half the distance between the peak and the wall. Connect the two rafters with metal gussets, fastened to each board with galvanized screws and a screw gun. Drive screws through holes in the gussets and put gussets on both sides of each rafter pair.

• 6

  Make gambrel braces with a cross tie between the two top rafters just under the peak and vertical support between the point the two rafters connect and the joist. Add a diagonal brace from that point to the joist. These should form two right triangles between the slope connection and the joist.