When TOH general contractor Tom Silva first heard about the fire-damaged 1893 house that would be renovated for TOH TV’s Season 46, he knew all too well what to expect: balloon framing. During the many decades he has spent renovating old houses in New England, Tom has worked on countless balloon-framed houses. “It was the most common style of building from the mid-1800s up until the 1940s,” says Tom.
Estimates suggest as many as 5 to 8 million homes throughout the U.S. today still have this construction method. The term ‘balloon framing’ was coined by early critics who compared it unfavorably to traditional timber framing, which used heavy, hand-hewn beams joined with mortise and tenon joints. By contrast, balloon framing used long, continuous studs of lightweight, mass-produced lumber that extended from the house’s foundation to the roof, making construction faster and more efficient. “Those early builders thought the structure was so lightweight and fragile it might float away like a balloon,” says Tom.
Fire Risks of Balloon Framing
Unfortunately, balloon framing increases the possibility of a fire getting out of control and destroying a house. Here’s why: The open stud bays allow fire and smoke to spread rapidly between floors. Since the stud bays are continuous, they act like chimneys and the fire can travel unimpeded from the basement to the attic in minutes. Also, fires can travel inside the walls without being immediately visible, allowing them to grow undetected until they reach an open space like the attic.
Because of the fire risk with balloon-framed houses, most houses since the 1940s have been built with platform framing, in which studs only extend one story.
How Fires Move in Balloon-Framed Houses
Tom collaborated with District Fire Chief Terrence Baudin, of the Worcester Fire Department to demonstrate how fire moves through a balloon-framed house versus a platform-framed house. Tom built a mockup representing three balloon-framed stud bays, then added pieces of wood and some mineral wool as fire blocking in one of the bays. “I expect to see lots more thermal progress through the open bays,” says District Fire Chief Baudin.
A team of firefighters lit Tom’s mockup on fire at the base, representing a basement, and then watched what happened. Indeed, smoke traveled up the open bays almost immediately in a chimney effect and flames took hold shortly after; meanwhile, neither smoke nor flames appeared in the fire-blocked bay. “The fire blocking really did its job,” says Tom.
Identifying and Fixing a Balloon-Framed House
How can a homeowner tell if their house is balloon framed? “The first clue is the age of the house,” says Tom. If it was built between the mid-1800s and the 1940s, it is likely to be balloon framed. “You can also go into the basement and look at the sill,” he adds. “In a balloon-framed house, the studs come all the way down and sit on the sill, with each joist nailed to the side of the stud.”
To reduce the fire risk in a balloon-framed house, there are several things that can be done. “The key thing you are trying to do is stop the draft and chimney effect in each stud bay,” says Tom, who notes that adding fire-resistant insulation, such as mineral wool, in stud bays is one way to create fire blocking. Drywall or lumber can also be added inside the wall cavities to stop fire from spreading. Sealing gaps where wires, pipes, and vents penetrate floors can slow fire movement.
As a preventative measure, consider upgrading any old wiring inside a balloon-framed house. Also, make sure to have your furnace or boiler serviced every year. “The typical culprits of fires that start in the basement are improper disposal of smoking materials, faulty electrical wiring, and improper maintenance of heating equipment,” says District Fire Chief Baudin.
The Fire at the Westford Historic Project House
The three-alarm fire that damaged the 1893 Westford house actually did much less damage than one might have been expected in a balloon-framed house. This is likely because the fire originated in the attic and never spread down the stud bays. Fortunately, for the current homeowners, that meant that beautiful original architectural features like the main entry’s grand staircase were virtually untouched. Even so, there was plenty of smoke damage on the second-floor’s ceiling joists, not to mention a totally destroyed roof and attic. Lesson learned: Fire block your house!
