We all have illusions about longevity. Many people think that a building’s strength is derived from its foundation, made of stone, or brick, or concrete, but that’s only partly true. A good foundation is a blessing, but a bad foundation is not damning. We’ve seen so many foundation failures that in a well-designed timber frame, we consider the foundation a sacrificial element.
The Lord Barn is one such example. Over the past decade, the barn had emulated a pat of butter on hot toast. Its fieldstone foundation was slipping, and the eave sills had rolled out from under the plates. The building looked dangerous to teenagers. With this kind of failure, we expected to find a lot of rot. But with the corrugated metal roof and deep overhangs, water infiltration was never the main problem. There was plenty of air flow, so bulk moisture wasn’t being trapped inside the building. While the foundation and undercarriage melted into the ground, the timbers above stolidly endured.
Dating a barn like this is hard, and not just because it’s a hot mess. Many of the larger beams, the tie beams, rafters, plates, and posts, are hewn, which means that their surface was smoothed with an adze or broadaxe, resulting in a texture like hammered copper. Hewing was replaced by up-and-down milling throughout the 19th century, depending upon proximity to a sawmill, and frugality. But the frame design and joinery of the Lord Barn follow later trends, especially the plate/post connection. The plates are discontinuous, and are joined into a mortise at the top of each post. The end of the plate rests on a 1″ let-in, or shoulder, characteristic of square-rule joinery, which became popular in the late 19th-century. Hewing is a labor-intensive and thoroughly handmade practice, while square-rule framing, although also cut by hand, was an innovation in efficiency that made pieces more uniform and interchangeable.
Both gable ends have integrated pocket doors, where the door slides through the middle of a 12″ deep post. Pocket doors look slick, but aren’t suited to this climate; the door and post expand and contract, and the gable sill isn’t well-protected. Arron says Tom Visser’s field guide dates interior pocket doors between 1870-1880, but I can’t find the book to quote it directly, so.
The roof system, with common rafters stacked over a principal rafter-principal purlin frame, is 1870s’ish. The common rafters are sawn and relatively small, 3″ x 5″. By stacking them over the purlins, the major roof framing is better protected. The rafters join the tie beam well inboard of the end of the tie, which means more material in the tie is resisting the outward thrust of the rafters. There is also better airflow around the principal rafters and purlins. In the Lord Barn, the common rafters run well past the plate, creating a deep overhang, which protected the sidewall framing as the sills slid and spread. The frame’s design brackets this barn between 1860-1880. We think it is a late example of a totally hewn frame.
When the foundation failed, the joinery was put into tension. In a pinned mortise and tenon joint, the pin prevents the joint from separating as the building settles and moves. But it doesn’t matter how strong the oak pin is once the relish past the pin hole gives way. In places where the joinery failed, tenon relish was the culprit.
The left eave sill rolled right off the foundation, pulling many of the left eave posts with it. It racked the entire frame, the posts pulling away from the loft girts. The tenon relish, just past the pinhole, was sheared in nearly every loft girt, and in many of the post tops, too. In bents where the post-tie beam connection held strong, the end of the tie beam dropped dramatically away from the rafter.
A year ago, we disassembled the barn with the entire crew. The clients, Pat and Paul Boisvert and Linda and Frank Underwood, de-nailed the timbers and helped dismantle the bents once they were on the ground.
Over the course of the summer, the clients had the foundation poured and built the floor system themselves. In the Fall, PTF made the few necessary repairs to the frame which included small repairs to a few post feet, and some face fixes where the pin had checked the cheek of a post or tie beam.
Almost exactly a year later, the whole crew came together again with the clients to re-erect the frame. Because of the discontinuous plates, a frame like this needs a lot of hands on crane day. We assembled each bent into two “H’s” on either side of the drive, with an eave post, a drive post and a loft girt. There were five bents and ten “H’s”.
We started in the left side aisle. The crane lifted the left rearmost “H”, and the crew stabilized it with a KD kickstand. Then two loft girts were installed, perpendicular with the first “H” and propped up with temporary deadmen. The second “H” was stood up by the crane and we worked in two teams of three to engage the loft girts. Two additional people on rolling staging lifted the plate and inserted it between the two eave posts.
When the first two “H’s” were plumb, all the joints were temporarily secured with KD gussets. At this point, the box was relatively stable, and we moved onto the third “H”. After the left side aisle was completed, we repeated the process in the right side aisle.
After a late lunch, the crane began flying in the upper triangles formed by the tie beam and rafters. The installation was complicated because the bottom of the tie beam needed to engage with four posts and four braces. Over time, a few of the tie beams had bent to conform to the drooping left eave, and each tie beam fit with some idiosyncrasy. Additionally, there was a pinned purlin between each pair of rafters. These beams needed to be installed by crew-members on staging at roof height. Before each tie triangle was flown, two staging towers needed to be dismantled and re-erected in the subsequent bay in order for us to be able to install those principal purlins. Every member of the crew and each of the clients were needed to erect the frame in a single crane day. It was a lot of fun.
Ultimately, the frame was saved, but the foundation was a lost cause. The relative flexibility of timbers and the strength of their joinery often allows them to outlast their granite and fieldstone foundations.