If you would like to know more about the brand new state-of-the-art seismic retrofit guideline, there are around 30 educational videos and web pages that you will find interesting. Just type ICC 1300 in the search box in the upper right.
ICC 1300 Vulnerability Based Seismic Assessment and Retrofit of One and Two-Story Dwellings’ approach to 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. Here you will learn what those options are and how to build them.
Cripple Walls and Balloon Framing Retrofits
Unlike a standard cripple wall which uses platform framing, balloon framing retrofits must be done without cripple wall top plates. In our video on cripple wall retrofits we talk a lot about top plates. We see a lot of balloon framed home built at the turn of the century until 1925 or so.
Split level homes such as the one shown above, which were common in the thirties and forties, almost always have balloon framing. This is because the main lower floor is nailed to the side of the garage wall. 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.
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 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 they were not put in too closer together which might 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.
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