Framing a House
The frame of the roof of the Cloverfields house has some unusual features. In the video above architectural historian Willie Graham tells us about them. He also describes the role that those exceptional elements play in the architectural history of the Chesapeake Bay.
When the house was initially built in 1705, the owner was a first-generation Marylander called Philemon Hemsley (1670-1719). Graham opens his presentation by reminding us that Hemsley was personally involved in the process of planning and building the house:
Our builder Philemon Hemsley, who constructs this house in 1705, is clearly engaged with his carpenters, and masons, and joiners in working out a structural system that is really specific to this building.
You know, it fits in a broader regional pattern, but he has to actually kind of tweak it to make it work. And he is also using some unusual structural features that do show up occasionally in American houses, but really are not very common.
Hemsley made some unusual choices for his roof frame. One of them was to use massive bent principal rafters.
Bent Principal Rafters Hold the Roof
The principal rafters are the upper diagonal members of a roof truss, and they are usually straight. What is notable about the Cloverfields’ rafters is their curved shape.
In the video, Graham stands in the third-floor attic, in the back section of the house. This is an excellent spot to show us one of the rafters. Graham tells us:
And so what you can see in piecing together… The first thing, are these big principal rafters. We call these “bent principals.” And this is one of the unusual features, that the principal rafters are cut to this bent shape.
The reason for that is to transfer the load of the roof directly to the principals and then from the principals to the top of the brick walls. This is a slightly… You need a place to see the bent principals because we are in a big open space, but what you probably don’t get from this picture is that the original stair tower came into the back of the roof out here. So we are not really seeing how the eaves came together, or the wall below it. We can see that in a minute.
But before showing us how the principal rafters connect to other pieces, Graham explains how they work:
The way these bent principals work is that these larger rafters are set up in pairs. They are timbered and pinned at the ridge, and then there’s the purlin above us, a horizontal timber that connects the principals together. And that purlin is used to not just stabilize these principal rafters, but it takes the load off the smaller common rafters that fill in between this principal’s base.
So here’s the form of these bent principals. So if we keep this in mind, why don’t we walk over to the eaves on the front of the building where we can actually see all the pieces together? And we can see how all that works.
Graham then moves from the back of the house to the front.
We are now in the eaves on front of the house, and what you are seeing right here is one of those bent principals. And that we see it coming down, and it’s tenanted to its tied beam. And that’s how we are able to create that truss action that makes these bent principals stable truss pieces.
And then what you might be able to see is two pegs that peg that joint together, to lock it all in together. This tie beam is sitting on top of the wall plate. So they lap it on top of the wall plate, and that’s sort of what locks in the house together front and back, and then the tie beams extend over on top of the wall plate. And this is where those bent principals really did their work.
Besides the bent truss, another unusual feature of the Cloverfields house is its classical cornice.
A Rare Classical Cornice is Integrated Into the Frame
In the video, Graham goes on to explain how the classical cornice is structurally connected to the frame:
So in the seventeenth century, we don’t really expect to see buildings that have overhangs, or jetties, or cornices on them. The idea of putting a classical cornice on a building is a new novelty if you will.
And the way they did it here is that they simply took the joist ends and they trimmed them out with moldings, painted them, and that became the modillions of this classical cornice of the front of the building.
What they are trying to do is load the roof, take the roof load and put it as close as they can over top of the brick walls so that they are not loading that on the overhangs of the joist, the overhangs that are necessary to create this classical cornice.
And so, by bending the principal rafters, and then on those principal bays they are putting on those short little… we call them “kick rafters,” but they don’t really kick in this case, they are rafter extensions so that they can keep the roofline going all the way up to the eaves. That fills in that space to the end of the joist of the modillions.
Graham then turns our attention to the false plates, and their “profound” importance in the Chesapeake Bay:
An invention of the Chesapeake that begins maybe in the 1640s is something we call “false plate,” and that’s this horizontal timber you see in the eaves where that little kick rafter sits on, and you’ll see that common rafters, and if you can look in through here you would see that all those secondary rafters sit on top of that false plate.
The importance of that false plate was profound for the region. The carpenters were trying to find every kind of labor-saving device they could, and what the false plates did for these early timber framers was…; it separated the joint of the common rafters from the joist so that they didn’t have to do a complicated mortise and tenon joint; it made the work go along a lot faster.
You can lay these horizontal boards in to simply miter the rafters to them, toe-nail them from the top and roll. So it was a very fast way of assembling a building.
Efficiency dictated the use of the false plate, a technique that, in Graham’s words, became “almost an American way” of framing:
And it became so ubiquitous that, the form of these plates might change a little bit over time, but I have seen false plates used as late as World War II in this region, even on military basis you’ll see them. It’s very common up through the First World War and becomes almost an American way of framing eaves, by using false plates. But in this early form, instead of being just a board it’s a thick heavy timber.
Graham then takes us back to the classical details. The choice of a classical cornice was rare, but the fact that it was integrated into the structure was even rarer. Graham explains:
What’s unusual about this house is that that timber sits on what appears to be a floor board so that instead of building the structure all as one piece and then laying all the trim in, Hemsley already realized that because he is going to have to a modillion cornice, he is going to… he needs to block the space above the modillions because it’s the joist that’s forming the modillions. He needs a soffit for its cornice. That’s going to be a painted board.
And so he lays his flooring in the house all the way to the outside of the eaves, paints the underside of that, because that’s part of the cornice, and then he lays his false plate on top of that board. So he’s really… before he’s raised the main roof, he’s already figured out how he’s going to treat the eaves and how all this stuff will be integrated together.
The classical decorative cornice was not an afterthought. Rather, it was planned from the very beginning by an owner who could frame the house in a way which would be both structurally sound and aesthetically appealing to him.
A classical architectural element, principal rafters that are bent, and false plates make the roof frame of this early eighteenth-century house worthy of notice. Of these elements, the ones that would become ubiquitous in the Chesapeake region are the false plates. The plates turn Cloverfields into a precursor of what Graham dubs an (“almost”) “American way” of framing. The classical cornice, on the other hand, stands as an early instance of experimentation in the American way of building classical architecture.
By: Devin S. Kimmel, of Kimmel Studio Architects, for the Cloverfields Preservation Foundation