Tie Beams are the defining component of a timber frame. They tie a barn together better than The Dude’s rug ever could. A tie beam crosses the gable at or below the plate (eave) level, and prevents the eave walls from spreading under the outward pressure of the rafters. Tie beams, more than any other element, identify the style of timber frame, be it English-tie, drop-tie, or interrupted. While a tie beam alone can’t date a building, these designs are associated with particular time periods; the English tie with the 18th and early-19th century, and the drop-tie with the 19th century (in Maine). I’ve written elsewhere about these impressive framing members, and the relative pros and cons to their design (Historic American Timber Joinery, by Jack Sobon, and made available by the Timber Framers Guild, is a fascinating and exhaustive source of joinery information). Below, I’m going to describe what goes into repairing one, in a standing building.
The owners of True-Randall Farm have a strong preservation ethic, combined with a desire to have their property serve their contemporary needs. They walked a fine line throughout the project, preserving every original, functional framing member, while installing a clean, contemporary kitchen in a long re-muddled connecting ell (preserving any remaining original framing even here, even though invisible). The house and barn on either side retain their original design and artifacts, as well as transitioning beautifully into a functional modern kitchen. The barn is visible through a sliding glass wall in the kitchen, where the expansive timber frame and associated repairs can be admired during meals.
The repairs to the barn were extensive. We replaced sills, foundation and drainage, and shored up the undercarriage. Two posts were replaced, along with their adjacent loft girts. Unfortunately, pernicious rot in the tie beam was invisible until exterior sheathing was removed to replace one of the drive posts. One of the advantages to timber frames is that a beam can rot extensively before losing functionality, or before the damage becomes visible. This is also one of the disadvantages.
The True-Randall barn has endured a history of alteration and adaptive reuse long before PTF or the current owners arrived. According to the history researched and written by owners George and Karin Look:
In 1889 the barn was moved to its current position and connected to the house by an ell. Local history indicates that it was rolled across the road using oxen and logs and that a small American Elm run over during the move stood back up and grew into a giant tree in front of the barn. The roof was removed before the move and roof elements, including the purlins, were used in building the deck for the barn, which was converted into a bank barn. At the time of the move an original eave wall was moved to the east 6 feet to increase the size of the milking parlor to accommodate the new, larger breeds of dairy cows that were becoming popular at the time. Also, the new roof was built with higher pitch to allow for storage of more hay. The barn was in use in a dairy operation until the 1970s.
In order to extend the barn 6′ east, a scarf joint was cut into the east end of each of the tie beams. As its name suggests, a tie beam functions in tension and any scarf along its length must equally resist those forces as any link in a chain. PTF’s commonly used halved-and-bladed scarf joint (p. 47, Sobon) is a great joint, but wouldn’t necessarily be effective here. The barn-wrights in 1889 used a stop-splayed, undersquinted and wedged scarf joint (p. 49, Sobon) to extend the tie beams by six feet and accommodate a new milking parlor. The two inch wedges in this scarf push the two halves of the joint together, countering the outward thrust of the rafters. This wedged key resists that force better than the shear strength of one inch pins (as would be used in other scarves). Additionally, the wedges can be driven into the key with seasonal and yearly wood shrinkage. This adaptive quality of wedges is employed elsewhere in timber-framing, such as the wedged-half-dovetail joint used at the ends of the Carpenter shop’s drop-ties, and in the wedged-half dovetail at the bottom of the king post in the Abyssinian Meetinghouse. The beauty of the wedge in a king post truss is that, being oriented vertically, the wedge drops deeper into the joint as the wood shrinks, automatically tightening the joint, like a glacially-paced Rube Goldberg contraption.
The front gable tie beam was badly rotten due to water infiltration. Located at the top of Randall’s hill, the front of this barn endures an inordinate amount of wind-driven rain, indicating the window directly above as the most likely culprit. The 18′ section of punky, rotten wood extended from the center of the drive to within 8′ of the rafter-tie-plate connection. We were fortunate that the rot didn’t extend to the English tying joint at the eave, as the repair would have required more complicated rigging and joint-cutting.
As it was, we built 3 levels of structural, wedge-lock staging across the plane of the front gable, extending from 7′ of lawn adjacent the gable into 7′ of the first bay of the barn. By crossing the upper ledgers of the staging with heavy, 8×8 rigging timbers, we were able to pick up the tie at two points, directly outside of the rot. The studs above were stabilized with a 2×10 hemlock ledger screwed across their faces. After the rigging securely supported the tie beam and framing above it, we carefully began to excise the rot. When we reached sound wood, we laid out half of a stop-splayed, under-squinted and wedged scarf on each of the two remaining ends of the tie beam. On the ground, we cut the analogous scarf halves on a piece of 9″ x 9″ x 18′ Eastern White Pine (we are currently avoiding the use of hemlock due to the preponderance of white mold).
We used a 1-ton chainfall, mallets and muscle to lift the repair into place and engage both scarves. The two hydraulic jacks allowed us to adjust the height either end of the existing tie beam separately, allowing us to dial into each scarf connection relatively independently. When each scarf was snugly fit, opposing wedges were driven in from each side, driving the halves of the scarf together and locking the repair in place.
Repairs of this level require extensive stripping of sheathing and clapboards. In the case of this barn, the clapboards badly needed replacement anyways. Some had been replaced ten or so years prior, with low-quality claps; others had been “repaired” with a spray of drywall screws. Inevitably, the replacement of sheathing, clapboards and trim takes as much, if not more, time than the timber frame repair itself.
While the condition of this tie beam was an unfortunate surprise, we were happy to be able to amend the damage with a traditional repair that blended seamlessly with the history of the barn, and its previous alterations. I can only hope that next month, the full replacement of a tie beam in a two-story Greek Revival in Brunswick goes as smoothly.