I’ve written about the differences between timber frame, balloon frame and platform frame houses in an earlier post you can read here, but I constantly get questions about how to tell if your house has balloon framing.
Why do people want to know?
Well, of the three types of framing, balloon frame houses have the greatest danger of catastrophic fires. To be clear, there is nothing intrinsically more flammable about a balloon frame house. It wasn’t built with kindling in the walls. The problem comes down to design.
What is Balloon Framing?
Balloon framing was the most common form of construction in America from about the 1880s to the 1930s.
In the 1800s, people started looking for a way to build houses faster and more inexpensively. Unless you were a skilled housewright, most people were unable to cut the complex joinery required for a timber frame house.
At this time, dimensional lumber (2×4, 2×6 etc.) was fast becoming available along with manufactured nails, thanks to the Industrial Revolution and railroads. This new standardized group of building materials would make balloon framing possible.
A balloon frame house is built using dimensional lumber fastened with nails, not joinery like the earlier timber frames. So, how is that different from how we build houses today?
Well, what makes a balloon frame unique is that the framing members run all the way from the mud sill to the rafters. These were much longer studs than anything we use today and since there was still a wealth of tall old-growth trees in America’s forests, lumber mills could make a 20, 24, or even 30 foot long 2×4!
What’s the Problem With Balloon Framing?
In this time period, most houses were built without insulation and these long continuous studs created hundreds of perfect, unobstructed, passages for fire to spread.
You see, in a platform frame (how we build today) there is a break between each floor in the stud bay called a top plate. A balloon frame doesn’t have this break and so a fire that starts in the basement can easily (and very quickly) spread to every floor of the house.
In the days of balloon framing, house fires were all too common and most houses didn’t survive long enough for the fire departments of the day to make much difference once they did get on site. Houses would burn down very fast and often didn’t allow enough warning for the people inside to escape to safety.
By the 1930s, platform framing was seen as the solution to this fire safety issue, not to mention the fact that we were running out of extremely tall trees. It made more sense to build houses with shorter pieces of lumber since that was not only safer, but also cheaper.
How to Tell If You Have a Balloon Frame House
It’s not always easy to see what’s hiding behind the walls of your house and old house owners from the balloon frame period of 1880-1930 have a right to be concerned since there is a distinct possibility they have a balloon frame house.
The issue of not having fire breaks between floors obviously isn’t a big deal for one story houses like many Bungalows or Mission style homes, but for other multi-story houses, it’s important to know what you have.
Unless your walls are opened up, it’s difficult to tell what kind of frame your house has. The attic is usually the best place to start looking. In a balloon frame, the 2nd story subfloor is held up on the edges by a ledger board instead of resting on the top plate in a platform frame.
If you look around the edges of the 2nd story subfloor or attic subfloor in a balloon frame house, you’d be able drop a penny down to the basement in the stud bay. In a platform frame, the penny would rest right there at the break between stories.
It’s not a perfect or scientific test, but for me, that’s usually the easiest way to tell unless the walls are all opened up for some other repair.
How to Make a Balloon Frame Safer
So, you have a balloon frame house, now what? Well, you want to be extra vigilant about fires for one thing. And if you can, it’s time to add some fire blocking to your walls.
Fire blocking is the process of adding horizontal blocks of framing lumber between the studs (especially at the breaks of each story in the building.
You’ll have to remove either the interior walls or exterior siding to gain access to the stud bays to add your fire blocking, which makes the process all the more difficult. These blocks of wood stop the fire from spreading up through the building and helps to keep the fire contained (for a time) to the lower story.
Is it always necessary to add fire blocking? No, but it increases the length of time to get out of the house in case there is a fire. Just like smoke detectors and fire extinguishers, fire blocking is a good way to ensure your safety.
In the end, a balloon frame wouldn’t discourage me from buying a house, but it is definitely something to consider.