Balloon framing is different from the methods developed by seismic retrofit contractors over the years. One never knows what one will find under these old houses, so it is always a good idea to know your options when building balloon framed shear walls. Here you will learn what those options are and how to build them correctly.
Main Floor Nailed to Side of Garage Wall Creating a Balloon Framing Condition.
Cripple Walls and Balloon Framing Retrofits
Unlike a standard cripple wall which uses platform framing and has top plates, balloon framing does not have top plates. In our video on cripple wall retrofits we talk a lot about top plates. We see a lot of balloon framed homes built at the turn of the century until 1925 or so.
These houses are built like this: The garage and another room (usually a laundry room) with same width and height as the garage is built first. The garage/laundry room usually extends 44 feet from front to back. Then the lower level floor is nailed to the side of the garage/laundry room walls. In other words, first they built the garage with the room above it, and then nailed the floor of the main house to the side of it. This creates balloon framing.
Balloon framing comes in many configurations and requires very specialized retrofit techniques that cannot be found in any of the available retrofit guidelines. Below are some images that show the difference between common cripple wall with top plates and balloon framing. Notice how the image on the right does not have a top plate. The floor is nailed to the side of the 2 by 4 walls.
How Should Balloon Framed Cripple Walls Be Retrofitted?
Here are a few balloon framing construction configurations that will give you a general idea of how these cripple walls are retrofitted. Houses that need balloon framing retrofits will have floor joists that are both parallel to the balloon framed cripple wall on two of the cripple walls, and the joists will be at right angles on the other two walls. Along the shorter foundations of a rectangular building this is the way the cripple walls are retrofitted.
Balloon Framing detail as found in ICC 1300 and FEMA P=1100 Vulnerability Based Seismic Assessment and Retrofit of One and Two-Story Dwellings.
This is an approach developed by a contractor that appears to have fewer moving parts. Many engineers have problems with staples, but I believe unjustifiably so. We use 2″ staples because nails split the wood. 6d nails could also be used so long as they are not put in too close together, which can cause splitting.
In the current conversion process from the retrofit standard FEMA P-1100 Vulnerability Based Seismic Assessment and Retrofit of One and Two-Story Dwellings into a national code, staples were discarded because of lack of testing. Nor are they part of any of the other seismic retrofit guidelines.
This approach to balloon-framing must be admired for its sheer simplicity. The simpler a design is the less likely it is for it to be mis-installed.
This one uses staples and blocking which is a simpler approach to some and more complex than others. We use this detail when the floor joists are nailed to the sides of the studs.
