The walls of your garage are bowed due to the weight of the roof pushing out at the top of the walls. A typical garage roof has rafters that form triangles that sit on the walls of the garage. Gravity along with the weight of the roof’s decking and roof’s shingles are pushing down on the rafters, which in turn force the ends of the rafters to push outward on the walls.
In many of the older garages I have inspected, the builders would install two or three ceiling joists or collar ties to hold the walls together. A collar tie is similar to a ceiling joist only it is attached higher up on the rafter to keep the rafters from spreading.
Here is what I would do when I was repairing bowed walls: If the rafters have a ridge board where the rafters come together at the peak of the roof, I would support the ridge with two long two-by-fours nailed together to form a “T” or an “L” shape for added strength and to prevent bowing. As the walls were being pulled together, I would put pressure on the “T” to raise the ridge board.
If the rafters are simply nailed to each other and there is no ridge board, then skip to the following suggestion.
Stretch steel wire cables from bowed wall to bowed wall at two or more locations at the top of the wall and next to a rafter. At the center of each cable I would install a turnbuckle, a screw-like device that when turned by hand pulls an eyehook located at each end of the turnbuckle. With each turn the walls would start to come together.
Once I had the walls where I wanted them, I would install a two-inch by six-inch ceiling joist every four feet and attached to the sides of the rafters to keep the rafters from spreading in the future.
The material costs to do this type of repair are minimal, less than $200, and can be performed by one person.
C. Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Send questions to C. Dwight Barnett, Evansville Courier & Press, P.O. Box 268, Evansville, Ind. 47702 or e-mail him at d.Barnett@insightbb.com.