Be Careful When You Back Up: Repairing Collision Damage In A Garage Wall

By Bruce W. Maki, Editor

Introduction:

It's easy to hit something while backing up. A parked car, a light pole, a guardrail... they all get in the way sometimes. Even a house or garage can become an obstruction to vehicular traffic.

This garage got in the way of a pickup truck that was plowing snow. The driver apparently hit the garage wall with the corner of his back bumper.

The damage was not readily apparent the first time I saw this garage. From far away the dent was hard to see.

The most obvious damage was the split in the casing to the right of the garage door.   From the right angle it was easy to see the dimple in the structure.

On the inside, there was a small built-in workbench directly over the effected area.   I removed the workbench to gain access to the damaged structure.

I noted several areas of damage:

• The bottom plate was split in two pieces.
• Several studs were split near the lower end.
• The worst damage: the T1-11 rough-sawn plywood sheathing was cracked and split, and wood fibers were sticking in all directions.
• The exterior door casing was split.

I began by removing the nuts from the anchor bolts. This was necessary so I could raise the garage structure slightly.

After my first attempt at raising the top plate, all I heard was the sound of nails popping... from up high. I knew that the top plate was being pulled from the studs. So I let the jack down and installed some metal framing braces. These are some sort of corner brace (made by Simpson Strong-Tie), which cost about a dollar each at Home Depot. I nailed the braces in place with 8d joist hanger nails.

Rafter ties would work for this task, but these braces seem to be more sturdy.

I again positioned the lifting post (red arrow) against the top plate. This was an old 4x6 deck post that I salvaged from a demolition job. I cut the post to the appropriate length, which was over 8 feet.  This garage had a high ceiling, about 10 feet high. With normal height buildings I would be able to use a steel lally column, which can be adjusted to many different lengths.

To raise the structure, I used my largest hydraulic bottle jack, a 12 ton jack. This was probably overkill... my 6 ton jack would have done the job. I like the larger jack because it has a wider base and a wider top pad, so it is more stable. I also used a piece of ¼ inch steel plate under the lifting post. This spreads the lifting force over the entire end of the post and prevents the top pad from sinking into the wood fibers.

With the jack and post positioned in a stable manner, I cranked on the jack a couple of times while watching the point where the bottom plate met the concrete block foundation wall. If the lifting was working properly, I would see a gap form between the cement blocks and the wood above it.

And that gap appeared just as I expected. I could push on this part of the garage wall and move it back and forth, which told me that the structure had been raised free of the foundation.

To gain access to the damaged studs, I pried the plywood siding/sheathing away from the framing.

Looking behind the plywood siding: Some of the siding nails pulled through the wood and stayed in the framing. I removed all the nails that I could find.

I used my reciprocating saw to cut the nails that held each damaged stud to the split bottom plate.

I completely removed the bottom plate so I could inspect the area.

I applied some urethane glue to the split parts of the bottom plate and re-assembled it around the anchor bolts. I clamped the board in two places. Then I drove in some deck screws on a low angle, to hold the two pieces together. I pre-drilled these holes with a countersink bit, which makes driving the screws much easier.

From the outside, I drove some 3" deck screws into the split studs, to force the two "legs" back together. Wherever possible I applied some urethane glue to the split wood.

One warning about screwing and/or gluing split wood back together: It's important to make sure there are no small chunks of wood or debris between the sections being fastened back together, or they will interfere with the proper fit of the broken pieces.

After all the studs were repaired, I slowly lowered the hydraulic jack. While lowering, I held the studs in the proper alignment with the bottom plate.

I fastened the studs to the bottom plate, using 3" deck screws and 10d nails. I also re-installed the washers and nuts on the anchor bolts.

To create a large solid nailing surface for the badly-cracked plywood siding, I nailed several pieces of blocking between the studs. These were positioned so they formed a continuous surface with the outside of the studs.

I also nailed some larger blocks of wood over the inside of the studs, to tie everything together. This extra step was probably not necessary, but I just wanted to provide some extra strength to the structure. Besides, I had the lumber available.

Correcting the cracked plywood: I placed a block of wood between the plywood and the wall, directly behind the worst part of the damage. Then I pushed on the lower edge of the plywood with my foot, in an attempt to force the splintered wood fibers into some sort of alignment. I was able to reduce the dent, but not eliminate it.

I nailed the plywood to the studs, using 8d galvanized spiral deck nails.

I heavily nailed the plywood around the cracked area. Some of the crack is still visible. The only way to make a better-looking repair would be to install a new section of T1-11 siding.

While I did this framing repair, I glued the split door casing with urethane glue and clamped it. By the time I was ready to re-install the casing the glue was dry. 

From a few feet away the flaws are not too obvious. The nail heads are more noticeable than anything else. A coat of paint would probably help a lot.

At least the dent is gone.

This was what I would classify as an "economical repair". Often the best approach to this type of repair is to remove all damaged material and replace it with new material. In this case, such an approach would involve 3 studs, a short piece of bottom plate, some siding and a piece of casing. But replacement would also entail removing the old jamb material from the doorway, which wasn't damaged but it was attached to the damaged studs.

Replacing the bottom plate by itself would be difficult because it needed to fit over the existing anchor bolts. For this reason I chose to glue the bottom plate back together. It had split at the anchor bolt hole locations, and I just reassembled the board around the bolts.

If the inside of a damaged wall had drywall, the wallboard would need to be removed to do this type of repair. Cutting out a piece of drywall and replacing it is fairly easy.

Copyright © 2003  HammerZone.com

Written June 2, 2003