I think most people on the crew have come across a frame that made them stop, and think, “Man, that’s the frame I’d build for myself.” I think I’ve found mine. It’s one of what will be three barns on a piece of property in Poland, ME – a horse barn, dairy barn and carpenter’s shop. We dismantled the horse barn over a year ago, on another property in West Poland; we’ll rebuild it next, and it’ll become a home for the client’s draft horses. The dairy barn is stabilized currently, and will need a complete undercarriage repair at a later phase. The dairy has some of the finest trim details I’ve seen on a barn yet, but it’s the carpenter’s shop that I love. It is a re-used frame, 17 x 30, with a drop tie, and purlin roof.
To a lot of folks, the English tying joint is the pinnacle of tying joints, but the drop tie in this shop is pretty charming to me. In any barn, the tie beam is the timber located at or near the top of the posts, parallel to the gable; it prevents the eave walls from spreading under outward thrust of the rafters. In an English tie, the tie beam crosses over the tops of the eave plate and posts; it is connected to the plate by a half dovetail joint (on the flat), and to the top of the post by a teasel tenon.
A drop tie beam is an early 19th century development, in which the tie beam is dropped below the plate by 2-5 feet and joined to the posts, directly. A collar tie is necessary to help prevent rafter spread, and the height of that collar tie is integral to it’s function.
In this shop, the drop tie is connected to the posts with a wedged half dovetail. An extended mortise is cut into the post, with a sloped bottom. The tenon on the tie beam is cut with a half dovetail (on edge), which drops over the sloped face at the bottom of the post mortise. After the tie beam is inserted into the post, a wedge is driven through the top of the mortise, above the tie beam, to help lock the joinery into place. A major difference between these two tying joints is how it affects the raising of the barn; an English tie would require an eave raising, and a drop tie requires a bent raising.
The benefit of a drop tie is that is provides higher head room in the attic story. In this shop, I thought the proportion of the room created at the attic level will be perfect for the client’s bench tools and hand work. The first floor will be used for machine work – the client plans to use the shop to restore antique sleighs. Both floors have enough headroom to spin things around and enough length to rip something as long as you’d like. It’s small enough to heat easily, and I especially like the way the light comes through the windows at the floor of the loft level.
Anyways, the carpenter’s shop was attached to the dairy, and was propping up its rear end. We dismantled the shop fully, both to repair it, and to move it away from the Dairy barn, which worked better for the site, and allows one to appreciate the beauty of the dairy more fully. It was a big help to have the client’s tractors on site.
Scott and Lee cut the replacement sill and post timbers quickly, and in the snow, too. They left for me the tie beams with the half dovetails that I love so. Lee followed his post work by cutting eighteen oak braces. The down braces at the loft level are part of what makes this drop-tie frame so durable.
Last week, we used our 8th grade geometry skills to lay out the frost posts. With the help of an enormous excavator, and a little mason’s line, it was a breeze to lay out the posts to the dimension of the shop’s footprint, but we needed to use the Pythagorean theorem to figure out what our diagonals should be, and make sure that the frost posts were laid at right corners to one another. It is a great joy of my job to get to use the theorems I learned in geometry class.
Next week, we’ll be topping the frost piers with granite capstones, and laying and fitting the sills over the granite. Lee has his adze sharpened, and we’ll be using it to cut the first floor joists. We’ll cut the joists to length and drop them upside-down into their associated cog-mortises in the tops of the sills and floor girts. Sitting in the cog upside-down, the rough floor joist will be 4-5 inches proud of the surface of the floor girts. We’ll then use an adze to cut an angled shoulder in line with the inside edge of the floor girt and to cut a tenon on the end of the joist that is perfectly level with the top of the sills. After the tenon is smooth, we’ll turn the joists over, and they’ll create a perfectly leveled floor.
We hope to raise the Carpenter’s shop frame in time for Christmas, and then our client can start sheathing it over the Holidays. I hope he thinks it’s an awesome present, because I would.