My 2 ½-story carriage barn, built in the 1890s, has walls that are bulging outward on the upper floor, just below the roof line. I am told that the building is “balloon-framed.” What does that mean and can this condition be corrected?
– Tom Giles, Bangor
Your barn’s not broken — it’s just tired.
Balloon framing first became popular in the 1830s. Unlike traditional timber framing, which consists of heavy posts secured with wooden pegs, balloon-framed walls are constructed with slim wooden studs that run uninterrupted from the sill atop the foundation to the horizontal top plate, just below the roof. These walls, often two or three stories, were typically braced diagonally for greater lateral stability. Because the stud walls could be cut from mass-produced lumber on the recently invented circular saw and nailed into place, they were cheaper and faster to erect than post-and-beam timber frames.
Some say lightweight balloon framing was named for its vulnerability to being carried away by wind. But this is not the system’s biggest failing. With balloon framing, the weight of the roof assembly is carried by the rafters. Where the rafters meet the outside walls, the tremendous force of this load is transferred to the vertical studs and carried down to the sills and foundation walls below. The weak point in the system is the area where rafters meet studs, or precisely where you’ve noticed bulging. Sagging of the ridgeline — a coincident condition — is often a symptom of the same problem. Factor in the additional burden of ice and snow building up over 120 years and you’ve got a weakened and potentially unsafe building.
Anticipating the rafter thrust that would eventually bulge the walls, skilled carpenters strengthened their buildings with collar ties — planks connecting rafters on either side of the roof — or with tension rods. These long iron rods with threaded ends were bolted through the top plates of outer walls and tightened using a turnbuckle. Unfortunately, in many historic Maine barns — especially those with haylofts — builders either misplaced the collar ties above their optimal height to allow for more storage space beneath or neglected to install them, or tension rods, altogether.
As a rule, if your walls are bulging more than two or three degrees, they require immediate attention to arrest any further horizontal movement. At Maine Preservation, we can do a pre-assessment to evaluate the severity of the situation and refer you to a qualified engineer and barn repair contractor. The most common solution involves pulling the walls back into an upright position using rigid tie rods or steel cables that are tightened, over a period of weeks or months, with turnbuckles. In some cases, it may also be necessary to jack up the ridgepole where it has sagged. Additionally, your contractor may advise reinforcing the building with properly positioned collar ties to further resist rafter thrust. With increased wind loading on walls and roofs expected from future storm events, you may also want to add diagonal bracing under the rafters and at the corners of the building.