Frequently dairy barns are divided into categories by the types of roofs they have. However, as made clear by Midwest Plan Service and other standardized plans, common stable types may have any of the three most common types of barn roofs. The decision as to which roof type to have was often based on the storage needs of the farmer, his or her financial position, and the availability of framing craftsmen.
Gambrel roof (USDA 1939).
Background: Due in large part to classic children's books such as The Big Red Barn , the image of a dairy barn to many, perhaps most, people, is a wood-framed, gambrel-roofed building painted red.
The gambrel, or two-slope gable roof, was introduced to barn construction in the post-Civil War period. By the late nineteenth century, eastern farmers began crowning their wood-framed barns with this roof. Also known as a curb roof, the double slope permitted a larger capacity hay loft without increasing the heights of the side walls of the barn. The Cultiavator and Country Gentleman discusssed the advantage of this roof type in an 1871 article:
Many farmers prefer the curb roof to their barns, as being more compact in shape, and possessing more capacity for the exterior covering employed. The greater height above the plates forms no objection where the pitching is done by the horse-fork...
The gambrel roof reached the height of its popularity in the early twentieth century.
Locations: Commonly found throughout the eastern and Midwestern dairy belt.Construction Techniques and Elements: Two types of framing were used to construct the gambrel roof: braced rafters and the plank truss or Shawver frame. The Shawver frame, named for carpenter-builder John L. Shawver of Bellfontaine, Ohio, was described by barn engineers W.A. Porter and Deane Carter:
The trusses...are placed 10 to 16 feet apart, with 12 and 14 feet as the usuala spacing. The trusses support the entire roof fload, and naturally heavier than the truss of the braced rafter frame. The space between the trusses is filled with braces and rafters The most widely used method of construction called for the building of the entire first story before the trusses were made and erected.
Porter and Carter also described the construction of the braced frame:
The distinguishing of the brace rafter frame is the fact that each set of four rafters is braced at all angles to form a light truss, which supports the roof through a length of two feet, which is the spacing of the rafters, no purlins or extra framing being necessary. Each truss consists of two lower rafters, two upper rafters, a collar beam or tie, and upper and lower braces.
Braced rafter construction (from University of Tennessee Agricultural Extension).
Shawver truss (Foster and Carter 1922).
Gothic roof (USDA 1939).
History: The earliest identified arched, rainbow or Gothic roof barn may have been a huge structure construction in Muscatine, Iowa in 1878 for lumber baron B.J. Hersehy. As with the gambrel roof, the purpose of the arched roof was to provide an unobstructed hay loft free of interior braces..
Locations: Gothic arched barns are most commonly found in the upper Midwest, particularly Wisconsin. An example from the outskirts of Racine is shown below. Although less common in other parts of the dairy belt, isolated examples are found throughout much of the United States.
Gothic roof barn. Racine, Wisconsin vicinity.
Construction Techniques and Elements: Early arched roof barns used curved rafters fabricated from single pieces of wood, while later examples used laminated rafters, construted of numerous pierces of wood.
The earliest multi-ply arched rafters were developed in the Pacific Northwest. These rafters were formed from one-inch thick boards, eight-to-twelve inches wide and three-to-four feet long, from which the outside edge was sawn to the required curvature. Three or four plies were laminated side by side with nails, and the splices were staggered to get the curvature needed. Due to the expense of wasted materials and the labor-intensive construction, farmers and builders were reluctant to embrace this technology.
Efforts followed to reduce the cost of fabrication and erection. A second technique employed bent or sprung rafters. This technique attracted attemtopm after a 1916 experiemtn in Davis, Califoria. The savings in labor and materials from sawed rafters led to the popularity of this construction techniques. Manufacturers of rafters usually built up four or five plies in one-by-four inch strips. Tightly clamping the strips in teh curved form withh the joints staggered at least four feet apart, the building then nailed them together from top and bottom.
Bent rafter construction, although less expensive in labor and materials than sawed rafters, proved less rigid. Many farmers combined elements of bent and sawed rafters with the sawed type rafter every eight to twelve feet and bent rafters in-between spaced 24 inches on center. In another improvement, the Louden Machinery Company, substituted in place of the sawed, curved rafter, a patented, curved reinforcing truss every eight feet that extended from plate to plate. In the 1930s, the use of glue yielded a stronger rafter bond.
Dimensions: Dimensions of Gothic arch barns offered by Sears Roebuck ranged from 40 feet long and 24 feet wide to 140 feet long and 40 feet wide.
Three types of gabled roof dairy barns (USDA 1939).
Background: As indicated elsewehre on this site,the primary reason for the development of the gambrel and Gothic roof forms was to provide additional storage for hay. In situations where the storage of large amounts of hay was not necessary because of a more moderate climate, gabled roof construction was often used for barns to reduce the expense of construction and the skill level necessary to erect the structures.
Locations: primarily in the American Southwest and West Coast where the winter climate was not as severe as elsewhere in the Dairy Belt.
Constuction Characteristics and Techniques: Three primary methods were used to framed gabled roof barns. In the case of wide barns, the roof must, of necessity be supported by trusses, posts or purlins as shown in the top figure below. The second means of roof framing, shown in the moddle below, uses a light framed truss of a standard type and provides a level ceiling for the stable, while the third type shown below, a scissors truss in which the members are secured by bolted steel collar ties, provides a sloping ceiling.
Gabled roof barn trusses (USDA 1939).