An enduring feature of timber frames is that they can be dismantled and re-used. A traditional barn-raising, in which a community comes together to erect a frame in one day is preceded by weeks of joiners’ labor: cutting and fitting the posts, girts and braces, plates and tie beams. With the help of many hands, or a gin pole, or a crane, a frame can be raised or dismantled in a day. The relative ease of assembly, and more importantly, disassembly, is why we sometimes find 300 year old frames in 200 year old buildings. The act of preservation and adaptive re-use is a centuries-old tradition, regardless of the age of the frame itself.
This year, engaging in this tradition has been equal parts fun and maddening. We were hired to decipher two frames tagged and disassembled by other contractors. One was the Reverend Morrison House, c. 1726, which was considered to be the oldest house in Londonderry, NH, and is being restored by the Londonderry Historical Society. The other is the French House, c. 1804, a 2-story hip-roofed house that was slated for demolition in Kingston, NH. It’s being restored by Charley and Sheila Foley, who are becoming old hands at this. Both frames were tagged before dismantling, but neither is attended by a full set of tagging drawings. We use tagging drawings like the picture on the box of a jigsaw puzzle. While we try to follow consistent tagging patterns, tagging a frame is pretty idiosyncratic. It’s unlikely that any two PTF frames would have tagging consistent enough to decipher the tags without drawings. That’s what made deciphering these frames such a…fun-show.
The Rev. Morrison House was dismantled with tags similar to our own. Alphanumeric codes identified the location of the piece, the type of framing member, and its number in a sequence. We could tell, based on timber size, and the half dovetail at its end, that SST1-SST7 were tie beams. But was SST1 at outside wall of the west ell, at the west gable, or at the east gable? And what did SS mean? We left that one a mystery.
Although a disassembled frame looks a little like a giant’s game of pickup sticks, it’s actually pretty easy to decipher how each timber was used. The joinery at either end of a timber communicates whether it was vertical or horizontal, and the joinery along its length tells us a lot about it’s location.
Knowing the English tying joint allows us to identify the timbers that establish the overall dimensions of the building. This joint is where the post, plate, tie beam and rafter intersect. The plate is a timber that runs parallel to the eave at the cornice and passes over the exterior half of the eave wall posts. The tie beam crosses the plate, directly over a post and directly beneath a principal rafter. Tie beams prevent the eave walls from spreading under the outward thrust of the rafters. The end of the tie beam end is cut into a half dovetail, and performs a mechanical task that contemporary builders assign to metal fasteners. More about tying here, and here. The plate accepts the tie in a half-dovetail-shaped mortise. In order to secure all this framing, the post is joined to both plate and tie. It is flared at the top, sometimes in an iconic, stepped “Gunstock” shape. The interior half of the post extends vertically past the plate and terminates in a “teasel” tenon, which inserts into a mortise in the tie beam.
We could identify tie beams by the half dovetails at either end, their size, 11″ x 11″ x 20′, and the long rafter mortise located right over the dovetail. The joinery in between will tell us whether the tie beam was located on either end of the building or across the middle. Tie Beams are located above the posts at the level of the attic floor. A tie beam from the gable end will have open cog mortises to receive attic joists along its top and interior faces. It will have closed stud mortises along its top and bottom faces towards its exterior, reference face. The reference face will most likely have a series of fastener holes left over from the sheathing. A tie beam from the middle of the building will look different. It will have cogs for attic joists along both sides. It will not have stud mortises on its top face, and it may or may not have stud mortises along the bottom, for partition walls. It was easy to tell the EPlate1 and WPlate1 were gable tie beams and the TS1 and TS2 were the interior ties. The carpenter who dismantled the building apparently considers all major beams that ring the post tops “plates” and, you know, that’s his prerogative. I guess he didn’t read this.
Plates, as we define them, run along the eave across the tops of the posts. In older timber frames like the Rev. Morrison house, they are smaller than tie beams in section, 6″ x 11″, but longer: 30′. The Reverend Morrison House has a long shed off its north wall and a shed off its west wall, too. The north shed plate was much smaller, 5 1/2″ x 9″, but 46′ long. This little plate received the short ties SST1-SST6 in an evenly spaced series of dovetail mortises. A plate will have post mortises and stud mortises along its bottom face. In18th and early 19th century timber frames, “English” timber frames, the plates will be the longest continuous framing members.
In an “English” frame, the post will be the easiest timber to identify. The Morrison house had beautifully stepped gunstock posts, 14′ 3′ long, 7 1/2″ x 9″ at the bottom and 8″ x 12 1/2″ at the top. The plate and teasel shoulders are offset from one another by two to four inches and the end tenons are oriented 90 degrees to one another. A corner post will have brace and girt mortises along two outside faces. Interior eave posts will have brace and girt mortises on opposite faces, and in a two-story building like Morrison, a second floor girt mortise on its interior face. The orientation of the stub tenon on the bottom of the corner posts will indicate how the original perimeter sills were arranged.
Perimeter girts will contain joist pockets that reveal joist orientation and joist layout. The Rev. Morrison house had an enormous chimney girt, 9″ x 14 1/2″ x 18′ 8 1/4″, and second story summer beam that connected the chimney girt and the east gable end girt, 10″ deep by 16″ across.
Once the timbers were identified, we were able to arrange the second and attic floors on the foundation that had been poured before the untimely death of one of the project coordinators. Just when the pieces were starting to fit together, the real mystery of this house was revealed. At the time of its dismantling, the building was a traditional saltbox shape. There were three bays, 12′, 8′ and 20′ wide, measured from reference to reference, west to east. We were told that the West bay (12′ wide) was a later addition, and the plates confirmed this.
The ends of the plates were totally weird. They terminated in a sloped, stepped shoulder that we’d never before seen in so many years of investigating scarf joints. The end of the plate was long incline, that was sliced to half its width, as in a sloped, vertical lap joint. But the shape of the joinery wasn’t the weirdest thing about the plate. The weird thing was that it extended past the second bent, past the second pair of posts, by about sixteen inches. While the ends of some tie beams extend past the eave walls to create an overhang, that is a later style that was clearly not the case in this building. The overhang is not mirrored on the opposite gable end, and the ties do not overhang the eave walls. The building could not have originally ended at the current second bent, because there would have been two oddly shaped plate ends poking out of the west gable end of the building.
But the length of the plates remained a curiosity, why did they extend west, past the outside faces of the posts? Additionally, the west gable wall posts were not continuous like the posts in the rest of the building. Ultimately, we determined that there were a pair of short teaseled posts on the first floor, with their teasels facing east, towards the main building. Originally, these posts were topped with a tie beam at the second story level, running perpendicular to the gable. Later, the tie beam became a second floor girt. A second pair of posts were cut and stacked atop the first, their teasels facing one another and linked with a tie beam parallel to those in the rest of the building. A single story ell preceded the saltbox roof on the west bay. Photos from the dismantling revealed that the chimney, located in the center, 8′ bay, was built with three fireplace openings, facing East, North and West. The fireplace opening and plate length indicate that a west-end, shed-roofed ell was original to the structure. The weird sloped shoulder cut into the end of the plate originally received shed rafters.
Investigating the tie beams confirmed our suspicions. When the building was dismantled, the tie beam on the west gable end was labelled “WPlate.” The next tie beam in was labelled TB1. TB1 served as the west gable tie beam when the building was built around 1726. Above, WPlate and TB2, a mid-span tie beam, lay next to one another. You can see attic joist pockets in TB2, and that they are laid out evenly until they get to the chimney mass, where there is a gap in the sequence. Both tie beams are hewn, but the hewing in the upper timber is more crude, and consistent with the quality of hewing on the plate extensions. The hewing in the rest of the frame was consistent with the fine hewing of the lower timber. The later timber is still quite early, and contains a number of wrought nails. This indicates that the west bay was converted from shed roof to salt box in the first quarter of the 19th century, at the latest.
It took us nearly a week to extract the timbers from the trailers, decipher their use and document their dimensions. We used that information, along with dismantling photographs, to create a scale 3D model in SketchUp. Using this information, the Londonderry Historical Society can restore the building, and decide the time period to which they will interpret. Ultimately, deciphering a dismantled frame is like a Times crossword puzzle, the degree of difficulty is matched by the feeling of pride and satisfaction in the solution.