June 27, 2014

Can garage with bowing walls be salvaged?

The concrete floor of an older detached garage is in good shape and has a new door. But the walls have started bowing due to high winds. The owner’s next project is to add a new roof, but he doesn’t want to invest too much in it if the walls can’t be fixed.

I have an older detached garage I use for storage. The concrete floor is in good shape, and I just installed a new door. After all the winds we’ve had, I noticed the walls are starting to bow. My next project was to add a new roof, but I don’t want to invest too much in it if the walls can’t be fixed. Do you have any suggestions?

The walls of your garage are bowed because of 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. The weight of the roof’s decking and shingles is 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.

If the rafters have a ridge board where the rafters come together at the peak of the roof, support the ridge with two long two-by-fours nailed together to form a “T” or an “L” shape for added strength to prevent bowing. As the walls are being pulled together, 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, 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, install a turnbuckle, a screw-like device that when turned by hand pulls an eye hook at each end of the turnbuckle. With each turn the walls should start to come together.

Once they are where you want them, install a 2-inch by 6-inch ceiling joist every 4 feet and attach 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 it can be performed by one person.

C. Dwight Barnett is a certified master inspector with the American Society of Home Inspectors.

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