Old barns, garages and outbuildings have a tendency to sag to one side so that the frame of the structure is out of square. Once this conditions is present, gravity continues to work, pulling the frame further out of square until the joints are too weak to hold and the structure collapses. Use steel cables in conjunction with hand winches, known as come-alongs, to right the structure so that the joints can be reinforced.
Locate the top and bottom frame boards just inside the front and rear walls of the barn, running parallel with the structure's length, perpendicular to the lean of the building. Look for a horizontal board running along the top and bottom of the wall. If there is no horizontal framing, locate the nearest studs to the front and rear walls.
Bore a 5/8 inch hole through the frame at the top of one side of the barn just inside the front, and at the bottom on the opposite side. Repeat this just inside the rear wall as well.
Thread a 5/8 inch thick eyebolt through each hole, with the eye to the inside of the barn, and fit a thick fender washer and two nuts on the threads and snug them down.
Stretch out the cable, or chains of the come along winches. Measure the diagonal distance between the two front eyebolts. Subtract the length of the winches cable from this distance and divide by two.
Cut two pieces of aircraft cable to this length, plus 6 inches. Thread the cabling through the eyebolts and fit a lock saddle on each cable and tighten the nuts so that the cable is firmly attached to the eyebolt.
Install a second saddle to create a loop of cable on the end opposite the eye bolt. Fit one cable to each eyebolt front and rear.
Attach the winches to the cables, one at the front and one at the rear of the barn. Ratchet the winches until the cables are snug. Tighten the winches one crank at a time, lifting the barn back up, taking turns so that both winches tighten at the same rate.
Place a level on the side of the barn that it is leaning away from. Continue lifting the barn by cranking the winches until the structure is upright and the level's bubble is centered in the indicator.
Use hurricane tie, or gusset plates to reinforce the joints at the top and bottom of each stud in the barn frame to secure it. Add additional lumber bracing second rafter along the length of the barn on both sides.
Release the winches, letting the tension off slowly, watching the level for signs of settling back into the original position. If settling occurs, tighten the winches and make further reinforcements until the winches can be released without the barn shifting.