Garage Remodel: Straightening A Leaning Garage

By Bruce W. Maki, Editor

Start:

While it's difficult to see in the photographs, this garage had developed quite a lean over the years. The structure leaned at least 1½ inches to the south, and about an inch to the west.

You can see a slight tilt when you compare the left corner of this garage against the corner of the neighbor's yellow garage.

The back (north) side of the garage.  The front side of the garage faces the alley behind the houses, a common situation in older neighborhoods.

The garage leaned about an inch to the west. Here the 4-foot level is held plumb (the bottom is against the wall) and there is a half-inch gap between the wall and the vertical level.

Using a flat pry bar, I removed the 1x4 corner trim boards. I knew that I would need a flat surface for attaching the hooks that the winch would pull on.

My friends asked me about repairing their garage a year before we worked on it, so I had plenty of time to ponder the technical problems. I knew that a stud wall assembly could be "racked" or squeezed on diagonally opposite corners to force the wall out of square. I call this "The Parallelogram Effect".  It's simple: if you take a rectangle where all the sides are sturdy, and one side (the base) is fixed to the ground, but the corners are not especially well-connected, you can push or pull on the rectangle and the rectangle will tilt, turning into a parallelogram:

Similarly, a parallelogram can be forced back into a rectangle, if one diagonal (the longest diagonal) is pulled together. Also, the shorter diagonal could be pushed apart. Which method is chosen depends on the tools at hand. I happened to own a pair of 2 Ton cable winches (also called a "come-along") as well as  6 Ton and 12 Ton hydraulic bottle jacks. I chose the weakest of my tools for the first attempt.

The First Attempt:

I attached a scrap of 5/4 x 6 deck board to one corner of the garage, using 3" deck screws. Then I attached a tow hook with 5/16" x 6" long lag screws.

On the diagonally opposite corner, I used a block of 2 x 6, because I didn't have any more thin blocks. I drilled a counter-bore for the 3" deck screws, so they would penetrate through the siding and into the studs at the corner.

It's fair to say that every mechanical system has it's weakest link. I knew that something in my tensioning scheme had to be that weakest link, but I couldn't be sure what. I could rule out some components that were clearly much stronger than others: the tow hooks (about 10,000 pound capacity), the chain (over 5,000 pound capacity), and the winch (2 Ton, or 4,000 pound capacity).

My gut suspicions, based on technical education and years of tinkering with houses, was that the connection between the tow hooks and the wood structure would be the problem area.

I was right. After connecting the winch and chains to the hooks shown above, I proceeded to pull the building. It may have moved a little, but I bent the 5/16" lag screws all to heck, and those small boards almost tore loose. I knew I needed something sturdier.

The Second Attempt:

Then I got serious and bought some hardware.

First, I tacked a pair of 2x8's to the corner, using 3" deck screws just to hold them in place. I picked up these big heavy-duty angle braces at Home Depot, and I also bought a selection of Simpson Strong-Drive lag screws, 3", 4½" and 6". I bolted the angle brackets through the 2x8's and into the garage structure. I used my heavy-duty ½" drill to drive these lags.

The purpose of these 2x8's is to distribute the pulling force over a larger section of the garage wall. I can easily generate the pulling force needed, but transferring that force to a wood structure is the trick. Since most common types of wood have a very low compressive strength (less than 600 pounds per square inch across the grain) and steel has a very high compressive strength (20,000 to 50,000 PSI) it's all too easy to punch a hole in the wood, or rip the bolts out, or tear a couple of boards out of the wall.

The intention of my "design" is to employ the steel angle brackets to pull on the 2x8's, which in turn spread the force over a larger area of the garage wall.

If I owned a welder, I would have rigged up some pieces of steel angle or channel to spread the forces over a large area of the wood structure. But... I don't own a welder... although watching all those episodes of Monster Garage has inspired me to consider buying a little MIG welder. Hmmm...

I needed to make sure that I had a solid structure to attach everything to. At the corners I added some small blocks of wood between the corner studs. I could have placed another 2x6 stud at this corner, covering the space between the original pair of studs. Metal framing connectors to secure the studs to the bottom plate might also be helpful.

For attaching the tow hooks, I could only use one of the holes in the bracket (red arrow) so I had to drill another hole.

The tow hook.  I bought 4 of these at about $5 each. These can be found in auto parts stores, farm stores, and Wal-Mart.

I used 3/8" x 6" lag screws, with two sizes of washers to help spread the clamping force of the lags. My next level of "escalation" would have been to use bolts with large washers... but that wasn't necessary.

I attached the tow hooks using a large ratchet wrench and socket.

The corner bracing, ready for duty.  Note the additional steel strap higher up. I'm not entirely sure this was necessary, I just figured it would help prevent the two 2x8's from separating under extreme stress.

I installed a similar brace at the diagonally opposite corner.

Note how the tow hooks are on a slight angle. This is to ensure that they are aligned with each other. If they weren't aligned, there would be unnecessary shear forces placed on the screws that hold the hooks in place, causing the screws to bend or break.

I hooked the business end of the 2 Ton winch to the lower hook...

...and I connected a length of 5/16" chain to the upper hook Note the slip hook on the end of the chain. Grab hooks won't work here!

But... the chain wasn't long enough. So I had to attach another small length of chain (this rusty section) with one of those openable links. Then the chain was looped through the stationary hook of the winch (see photo below), and connected to itself with the grab hook.

I cranked the winch.

A more complete view of the pulling rig. The red arrow points to the winch. This is the west wall of the garage.

At the same time I set up another rig on the east wall of the garage. I tightened each winch a few clicks at a time. It might be better to have one person operate each winch, but it's not necessary because the building will easily flex a small amount. I took my time, cranking on the winches and then letting the building "take a break" for a few minutes. There's no hurry.

That long 2x4 on the wall was just hanging around. At the time, it was only attached at the top with one screw. I later fully secured it to the studs, to keep the garage from returning to its leaning state. And I did the same on the west wall.

On The Inside: Keeping It Stiff

The inside of the garage, looking towards the garage doors.

The same wall, viewed from the door opening. Note how the siding was nailed directly to the studs, and there was no "let-in" bracing, which was commonly used in those days.

One problem I faced was the presence of a topping slab, or extra layer of concrete on top of the original slab. This new layer had been poured against the bottom plate, so I could not nail any bracing to that wood.

Steel T-Bracing, about $5 at Home Depot for a piece about 12 feet long. This stuff can be found in Home Depot's lumber department, near the Simpson Strong-Tie framing connectors. Every piece my local store had was bent from being hit with a forklift. Typical.

T-bracing is meant to run from the top plate to the bottom plate, running diagonally across the face of the studs. Normally this bracing is installed on the outside of the studs, during framing. The only choice I had was to attach the T-bracing on the inside of the stud wall. I held the T-bracing in place and marked a line above it...

...like this. I held the material backwards for the purpose of marking the cut line. Actually, I think I drove one or two nails through the metal to keep it from moving.

I removed the metal and made a shallow cut across each stud, using a circular saw set to a depth just a bit more than the bracing.

I hammered the bracing into the grooves and nailed it in place with Simpson 8d galvanized joist hanger nails. I was going to pre-drill the holes in the metal, but I discovered that I could easily drive the nails through the T-bracing.

I was lucky that the window opening was not in the way of the bracing. Bracing will still be effective if it has to be cut and then angled the other direction, like a sideways "V" shape. As long as the bracing extends from the top of the studs to the bottom, it will add stiffness to the wall structure. The more studs crossed, the better.

The preferred method of attaching this T-bracing is to run the metal from the bottom plate to the top plate, nailing it to all the studs that it crosses. If either (or both) of these plates were not accessible, the bracing will still help to stiffen the structure, but the connection between the studs and the plates should be beefed up with steel connectors.

Another view of the brace. This took only a few minutes to install. I installed 6 braces in all, two on each of the three walls. The fourth wall was entirely a doorway, though that was changed a few weeks later.

These simple pieces of steel made an enormous difference in the stiffness of the garage. An alternative to steel T-bracing would be to fasten a sheet of plywood to the studs at both ends of each wall. The homeowner wanted to be able to access the wiring, which would have been impossible with plywood bracing on the inside.

Note that many structures today are built with some sort of rigid sheathing (plywood or OSB) applied to the outside of the the studs. This sheathing acts like the diagonal bracing shown above. In fact, it's only necessary to install the sheathing at the corners of the structure to achieve decent stiffness in the structure. Some builders take this lower cost approach, and use foam insulation for the remainder of the sheathing, which gives some improvement in overall insulation R-value.

In my opinion, there's no way you can effectively correct a leaning structure unless the outside or inside wall surfaces are removed so bracing can be installed. On a residence this is not a minor repair, and I would only approach this in conjunction with other remodeling projects, such as siding replacement. On an unfinished garage this repair is relatively minor.

More Projects On This Garage: Replacing The Sill Plate (Bottom Plate)

Copyright © 2003 HammerZone.com

Written March 3, 2003