By the fall of 1792, George Washington fully developed plans for the barn complex at Dogue Run, one of five working farms on his 8,000-acre estate. The new barn was to perform the same function as the English-style barns Washington had been studying for many years—grain processing and storage—but in a radically different manner and with several novel features.
Washington was well acquainted with using animals to separate grain from stalk by treading, and he had very specific goals in mind that he wanted to achieve. Beginning with a simple concept—to construct a circular wooden treading floor large enough to accommodate horses that were enclosed from the elements of weather—Washington sought to improve the efficiency of this basic treading process and simultaneously reduce opportunities for theft. The barn included a treading floor located on the second floor of a two-story structure that the horses could access via an earthen ramp.
Washington conceived of the innovation of leaving spaces between the floorboards so that the heads of grain, once separated from the straw, would fall through to a granary below. There they could be temporarily stored in a central octagonal structure, then winnowed, and sent to the mill. The result was a building that was conceptually as much a machine as it was architecture.
Polygonal structures were unusual but not entirely rare in eighteenth-century Anglo-America. Although the shape was the structure's most distinctive feature, it was not the polygonal shape of the barn that was Washington's innovation. Rather, the innovation was in taking an agricultural process and designing a structure to accommodate it. The roughly circular footprint was chosen to facilitate the treading of the horses. The reason for the structure being polygonal instead of perfectly circular in shape was due to the greater ease of constructing straight sides instead of curved walls.
The selection of sixteen sides rather than any other even number is more difficult to explain, although it was also probably related to the octagonal shape of the interior framing system. Since the treading floor was to withstand the weight and punishment of trotting horses, durable white oak was utilized. Most of the remainder of the wood for the barn, except the roof and the ground floor interior octagon posts, was made of pine.
Although it appeared steep, the slope of the barn roof (approximately forty-three degrees) was not unusual for eighteenth-century buildings. Roof pitches between forty-two and forty-eight degrees are typical for this period. The general reason for such a steep pitch was that it encouraged faster run-off, resulting in less time for water to penetrate the wooden shingles.
Because the barn has an unusual shape, it must have been a difficult building for Thomas Green, Washington's carpenter, and the Mount Vernon slave carpenters to construct. One of the most important decisions Washington made was to design a building comprised of two nested polygons. This refers to the sixteen-sided outside wall, enclosing the interior octagonal framing system. This design was the most straightforward way to support the roof since the same system for laying out the rafters could be continued from the eaves to the peak of the roof.
The transition from the exterior sixteen sides to the interior eight meant that the structure of the roof had to undergo some subtle adjustments as construction continued upward, including the reduction of the number of rafters from eighty to forty-eight. Since the rafters were the only structural members spanning that space, they served the crucial function of binding the exterior wall to the frame.
Dennis J. Pogue, Ph.D.
Fusonie, Alan and Donna Jean. George Washington, Pioneer Farmer. Mount Vernon, VA: Mount Vernon Ladies’ Association, 1998.
The Writings of George Washington, ed. John C. Fitzpatrick Washington, D.C.: United States Government Printing Office, 1931-1944, Volume 32: 285-291, Volume 34: 435.