How to Repair a Cracked Roof Truss

Use a power drill equipped with a metal bit to drill a series of eight 1/2-inch-diameter holes into a 24-inch-long piece of 1 1/2-by-1 1/2 inch steel L-channel. There should be four holes in one side of the channel and four holes in the other. Space the holes evenly so they run from one end of the channel to the other.

Clear away any broken pieces or loose wood from the cracked truss with a reciprocating saw. Hold the L-channel onto the broken truss so that it is more or less centered over the crack. Use the drill to make four pilot holes through the holes at one end of the channel and into the truss.

Use a ratchet set to drive four 4-inch lag bolts through the L-channel and into the truss. With the steel fastened to the truss at one end, you must now bring the truss back to its original shape. Measure the gap between the bottom edge of the L-channel and the underside of the truss. Select two lag bolts that are about 2 inches longer than the measurement you took.

Drive the long bolts through the bottom L-channel holes and into the underside of the truss with the ratchet set. Alternate between the bolts, tightening a few turns at a time, so the wood and L-channel come together evenly. Continue until the truss returns to its original position and the crack is closed.

Drill pilot holes through the two remaining holes in the side of the L-channel. Drive two lag bolts into the pilot holes and fasten them with the ratchet. Install a second piece of L-channel onto the opposite side of the truss for extra support. Stagger the pilot holes and lag bolts in a different order so they do not cause weak points in the truss material or meet halfway through.