How to Build a Roof Beam

Sight down the edges of your 2-by-12 lumber to determine which edge the crown is on. Most boards have a slight bend in them, and the side on which the high point of the bend is in the middle is called the crown. When you put the 2-by-12s together, be sure that all the boards have the crowns on the same side.

Lay a 2-by-12 on flat ground in a location where you have easy access to all parts of it. Spread construction adhesive over the face of the 2-by-12 in a zig-zag motion with a caulking gun, making each zig-zag about 6 inches in width.

Place a second 2-by-12 on top of the first. Arrange the boards so that their sides and ends are perfectly aligned. Tack the two boards together by driving 2-inch nails into each end. Spread construction adhesive onto the face of the second board.

Lay the third board on top of the first two boards. Align its sides and ends with the other boards. Tack the third board to the second board by driving a 2-inch nail into them at each end.

Nail the third board to the second and first board with 4-inch spiral nails. Drive five nails in a row at the ends of the boards then another row of five nails 12 inches down the board. Continue all the way down the board, driving in rows of five nails spaced apart at 12-inch intervals.

Turn the three-board assembly over to reveal the outside face of the first board. Nail the boards together from this side as well, driving rows of five nails in the middle of the gaps between the nails from the other side. When you are done, your boards will be nailed together by rows of five nails every 6 inches, with the rows of nails entering the boards from alternating sides.

Draw a square line on the ends of the three-board assembly with a carpenter's square and pencil. Cut the ends of the assembly off to create perfectly square ends and to make the beam the necessary length.