In 30 years of investigating New England’s historic churches, PTF has never encountered a better truss system than that of Eastport’s Central Congregational Church. Built in 1828, the roof system combines the traditional strength of a king post-prince post truss and principal rafter-principal purlin roof with innovative tying geometry that prevents the pitfalls of rafter slippage experienced by other churches we have investigated. The roof geometry has maintained its joinery even though the foundation appears to have suffered a landslide into the basement of the church, and most of the carrying timbers are being carried by their floorboards.
The exterior façade stands out for the near complete preservation of its original composition and trim detailing. It serves as a prime example of how some Federal Era builders used relatively simple building methods and a small collection of hand tools to create arresting architecture by integrating detailing with overall composition of fenestration and major trim elements. The proportions of the pilasters are arresting, but the trim is not ornate. The pilasters are not fluted and the capitals have a simple, muted profile, devoid of carvings. The capitals are incorporated into the architrave and terminate at the full length gable return, which is deep, but has a short fascia. The pilasters terminate neither in an efflorescence like late Federal, nor in a broad stripe like Greek Revival. Instead, the return is a fine line. An eyebrow window, the width of the center third, punctuates the tympanum. The sash is decorated with three ovals drawn in tracery that repeat the rhythm established below. The building presents a façade that is both austere and elaborate. Austere in that the building is embellished exactly to the degree necessary to show reverence for the building’s purpose, and no more. Elaborate in that the design reflects a serious consideration for proportion and how every detail relates to the whole.
The failure of the foundation can be seen from the outside of the building. In many places, the grade almost reaches the bottom course of clapboards. In the rear northwest corner the foundation stones have caved in. A river runs through the right north bays of basement, where the clearance is 6’. The grade slopes upward to the south; the clearance in the southern joist bays is 1’ – 2’. Bulk moisture and lack of ventilation have deteriorated the timbers over time and the carrying beams bear the scars of inadequate repairs and forced-air heating ducts. The two rearmost carrying timbers are no longer connected to the sills, and the third is fractured. A replacement sill, under the narthex, is undersized, so that the adjacent joists don’t quite reach it. Fortunately, most of the joists are so oversized that they will function ably after the exterior ½” of slough is removed with a drawknife.
In the process of undercarriage replacement, much of the foundation will also need to be rebuilt, and as much of the grade removed as possible to reveal pier footers and ensure good drainage and improved ventilation. Foundation and grading will comprise the bulk of repairs.
The roof system has withstood the extreme deterioration of the foundation and undercarriage due to its exceptional design and level of craft. To the layperson, the Central Congo truss system is beautiful; the hewn surfaces of the timbers are shiny from the use of a sharp adze, and gently mottled, like hammered copper. At the center of the truss, the broad diamond-shaped head of the king post hangs from the apex of the rafters. Its long slender neck widens at two sloping shoulders from which two struts spring. Two wedged braces form an “X” connecting the trusses along the longitudinal axis. The struts each land in a undersquinted notch at the head of a prince post, from whose knees spring yet another pair of struts. There are two additional struts, or jack posts, just outside of the prince struts.
To the timber framing professional, the roof system is sublime. The truss itself is at the peak of craft, from the detailed shaping of the king post to the undersquinted joinery at the prince posts. The bottom chord, or tie beam, 10” x 11”, appears to have forced camber so that its center is 2” higher than its ends. The king post/bottom chord joinery is reinforced with an iron stirrup, fastened with butterfly bolts. Not only is the truss exceptional, but they are tightly spaced, less than 10’ 6” on center. But it is the framing between the trusses that is truly innovative. The roof system is a principal rafter, principal purlin roof, with common rafters between the trusses. The principal rafter, or upper chord, is 9” wide, and tapers from 9” deep at its apex to 11” deep at its foot. It is connected to the next truss by a horizontal beam, called a principal purlin. The purlin is parallel with the eave, and about halfway down the roof pitch. Between the trusses, there are three common rafters. In a typical church roof, these commons land on a flying purlin that is joined into the ends of the adjacent tie beams. The problem with this design is that the tie beam is already missing a good chunk of material from the rafter mortise, and the rafter is actively pushing outward against the relish on the end of the tie. The flying purlin is often too undersized to really resist the thrust of the common rafters, and bows out and blows out the end of the tie beam, further compromising its joinery. Commonly, this results in the upper chord of the truss slipping out past the end of the tie.
In the Central Congregational roof, there is no flying purlin. Instead, each common rafter lands on its own short tie beam, perpendicular to the eave, which runs over the top of the plate and ties back to a ceiling purlin connecting the trusses. The ceiling purlin is 9’ from the end of the tie so it doesn’t compromise the rafter joinery. The ceiling purlin and short tie are substantial. They are strong enough to actually resist the outward thrust of the common rafters. This means that the rafter mortise in the end of the tie is resisting a lot less thrust, and not a single one is blown out or even slipping. Additionally, the principal rafters are fastened to the bottom chord with an iron trunnel pin. The short tie solution is also found in the North Free Will Baptist Church, just up the road, and appears to be unique to Eastport. The truss system appears to be free of rot or any other damage.
The tower was significantly rebuilt in the late 20th century, and while the repairs were not in-kind, they appear to be functioning. With the exception of one girt stabilization, all the tower needs is a good reaming and a coat of paint.
The octagonal belfry and spire have clearly been through multiple generations of repair. The original spire was blown off the building in the Saxby Gale of 1869. This apparently does not include the belfry, much of which was also rebuilt in 1986 and 1994. Above the tower plates, the eight spire rafters join directly to their posts about 5′ from the belfry floor. There is no intermediate horizontal girt level for them to land on; the spire rafters join the tower posts at the center height of the louver openings. At the louver header, each spire rafter is further secured to a tower post by a 1 ½” iron stirrup that wraps around the rafter and is bolted to either side of the post. The belfry plates do not cross over the tops of the plates, they intersect the plate 6” below the top of the post. The tower posts terminate in a level cut. A belfry roof rafter connects the top of each post with a spire rafter.
Access to the building has improved significantly since our first visit in summer of 2015. The removal of substantial pigeon detritus and installation of lighting is a testament to the high-quality stewardship of the Tides Institute and Museum of Art. The organization stands out for its initiative, community involvement, and generation of momentum. TIMA is clearly committed to the continued preservation of its historic structures.
This blog post is a severely abridged version of the Central Congregational Church assessment that we performed for the Tides Institute this spring. TIMA has published a lot more about the building’s history, here.