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Some of the earliest silos built from masonry components are still standing today, many with little to no continual maintenance. In contrast, wooden stave silos seldom survived. Researchers Henderson and Isern noted that in all of their travels and studies they knew of only one that still stood in the Plains states.13 There were several different types of masonry construction. A wide variety of materials were used in the construction of silos. Brick was a natural candidate; however, they were not usually used because of their high cost and the need for skilled labor in the construction process.
After the development of natural gas in the early 1900s, cheap gas-fired ceramic hollow blocks became a material of choice. (Figure 5) Extremely popular, these ceramic block silos are still seen standing on many farms in the Midwest. Ceramic building material was durable, attractive, and helped insulate the silage from freezing. The dark brown and glossy appearance of fired tile proved to be a popular addition to farmyards and some companies offered farmyard “kits” that included tile barns, silos, and other miscellaneous outbuildings in a coordinating scheme. Kits were obviously quite expensive and proved to be shortlived, as farmers seldom wanted the added expense of coordinating their farmyards with a unifying construction material theme at an added expense.14 There were some disadvantages however, such as the brittleness of the tiles. An accidental collision, even a surprisingly light one, could crack a lower tile leading to problematic replacement issues.
Additionally, acidic liquids formed during the ensilaging process tended to eat away at mortar. Some companies did produce a special tile that reduced the exposed area of the mortar, but some preventive maintenance was still necessary. The final and most important disadvantage was that, as often occurred in the evolution of any 13 Noble, “The Evolution of American Farm Silos”, 146. Henderson, “Wooden Silos of the
utilitarian structure, cheaper and easier methods of construction eventually developed.15 Soon after the turn of the 1900s, farmers began to use a quick, easy building material-cement. Cement gave way to concrete, which quickly became the building material of choice. This preference took a variety of forms in the construction of silos. Some farmers were able to produce their own concrete blocks and then erected a homemade silo.
But commercially-made concrete blocks were also popular and created an attractive, durable, and long-lasting silo at a low cost. Concrete blocks were usually smooth, but some were crafted to include a roughed-out appearance adding an aesthetic quality to the farmyard landscape. Vendors offered a variety of styles which included straight blocks and curved blocks, hollow and solid, and blocks with built-in reinforcement. Block options did not change the outer appearance much, with the exception of choosing curved over straight, but they did create a more durable silo. Curved blocks were more costly, but they gave the silo a smoother appearance on the outside.16 Another form of concrete construction was closely related to an earlier design. The wood stave silo inspired the concrete stave silo.
(Figure 6) The concrete stave silo was built much like the wood stave silo except that the concrete staves were usually only approximately 30 inches long. Short staves were built so they could interconnect with one another. As the silo gained height, bands much like the bands used on wood stave silos were placed around the structure to hold it together.
This allowed the farmer to add to or remove height as need or financial ability allowed. (A silo showing this growth is on the right-hand side of Figure 6; note the band of colored staves near the middle, showing that this layer was once the top of the silo.) The concrete stave method was quite popular and many of these silos are still seen and built today in the Midwest. They are distinctive in their appearance due to the vertically striped look and the decorative elements that builders tended to include near the top such as contrasting colored staves in an alternating or solid band. The concrete stave silo was the first style that was universally popular in not only the Midwest, but the rest of the country, therefore becoming the standard in the silo “look.” Consequently, the concrete stave construction technique is still used today.17 The final concrete construction method was that of the monolithic silo. (Figure 7) The monolithic silo was one solid tube of 15 Noble, “The Evolution of American Farm Silos”, 138-48, 146-47. Henderson, “Wooden Silos of the Southern Great Plains,” 3.
16 McCalmont, Silos, 29. John C. Wooley, Farm Buildings (New York: McGraw Hill Book
concrete, poured more or less at the same time resulting in a seam free and remarkably solid structure. With the monolithic construction technique, air leaks were no longer a concern and exterior structural support was no longer necessary. These silos could last almost indefinitely with minimal to no maintenance. Monolithic silos proved to be especially popular and came to replace other silo construction techniques as the preferred method. Construction costs were comparable with other methods and required only the use of slips and concrete supplies.18 The monolithic silo appeared across the Midwest as well as the rest of the country. They were easy to discern from other construction techniques due to their clean outward appearance. Monolithic silos had no exterior supports; the reinforcement was all located within the concrete itself, eliminating the hoops seen in many other techniques.
They also usually featured an outside dressing that made the silo appear seamless. Of course, some were left unfinished with the slip form marks still visible, but many were finished with a surface coating of cement and paint that created a more finished look. The smooth surface lent itself well to being decorated, and many farmers personalized their silos with personal or commercial messages. (Figure 8) Monolithic construction was the construction technique also used by many grain elevators who took advantage of the large uninterrupted canvas to place their brand name and other advertisements on the exteriors.
The final type of silos was the bonded fiberglass silo, commonly known by the brand name “Harvestore.” (Figure 9) These silos developed in Wisconsin in response to the long known fact that the removal of air results in the highest quality silage. Harvestore silos were made from fiberglass bonded to curved sheets of steel and then formed into an airtight structure. To allow for atmospheric change, they featured a large bag inside to adjust the pressure. An added feature of the Harvestore was the automated system built in for ease of unloading, which featured an auger that removed silage from the bottom of the silo rather than the top, as in earlier styles. This new feature created two advantages. First, it did away with the need for the outside chute and ladder and farmers no longer needed to climb to the top daily to unload silage. Second, silage could be continuously added to the top of the stack eliminating the need to completely empty a silo before filling it again.19 Harvestore silos came in a brilliant blue color that made them instantly recognizable from any other silo. The blue color resulted from the inclusion of the mineral cobalt in the glass material which is bonded to the steel. This was a choice based on the availability and affordability Rabild, Homemade Silos, 2. Eckles, The Silo and its Use, 11.
of bulk material at the time of the development of the Harvestore brand.
The blue color has since become an identifying feature of all Harvestore structures to present day.20 With all of the conveniences of a Harvestore silo came a hefty price tag as well. The large investment only made sense for certain farmers who had a large herd feeding in a single location, such as a dairy operation. This was the target market for Harvestore silos, and their regional popularity reflects the type of cattle industry in that area.21 There are several features of silos that have changed over time that provide the viewer with a fascinating look at the evolution of silo construction methods and design features. Aspects of the silo, such as doors, windows, roofs, and chutes allowed such a simple structure to take on many different appearances and styles. By examining some of the features of a silo, an observer can identify a popular style in a region, or even different options offered by a local contractor.
Silos originally did not include a roof over them. Tests by agricultural colleges and firsthand experience of farmers proved that rain and weather had little effect on silage. A roofless silo did result in slightly increased spoilage, but many early silos remained roofless for ease of filling and unloading the silo. There were many advantages to a roof, such as protection from the weather, keeping out birds, and generally better quality silage. Roofs also increased the stability of the structure, decreased weatherizing, and improved the appearance. There have been many different types of silo roofs, but some of the most popular were gambrel, half-pitch, and dome roofs. The farmer or contractor selected the style individually, but the reason for the roof remained the same; a higher roof meant more headroom and more silage capacity. Some silos were built to match the roof of the barn in a gambrel fashion. Some of these gambrel roofs featured a dormer with glass windows serving a dual purpose, to allow light into the silo and as a potential access point for filling the silo. The most commonly seen roof today is the half dome, especially on concrete stave and Harvestores, due to the ease and rapidity of construction.22 Many older silos originally had chutes attached to the side. Many of these were removed as modern equipment updates eliminated the need for them. Automatic silage unloaders replaced the chore of the daily climb into the silo to pitch silage down to the ground below. To protect the farmer from weather, and to provide a chute to prevent the scattering of silage as it fell, enclosed chutes anchored to the side of the Harvestore Sales Representative, e-mail message to author, May 1, 2010.
20 Noble, Barns of the Midwest, 109.
21 22 Chas. M. Conner, Forage Crops. The Silo. (St. Augustine: The Record Co., 1905), 300.
silo were built. Chutes contained the doors and the ladder, the latter of which sometimes consisted simply of the reinforcing rods holding the silo together. Chutes were square and wooden in most wooden silos, but as concrete came into use, chutes became round and made of metal.
Many concrete stave silos still retain their rounded chutes.23 Doors on silos also changed greatly over the course of silo evolution. Multiple doors were convenient on silos to access the silage at different levels of fill. Early silos had few or no doors due to construction methods unable to support a hole cut into the side. Early publications noted that if a door was desired, to make sure to not place them over each other to improve the stability of the silo. That was the reason for staggered doors in early constructions. As methods improved, the number and size of doors increased. Eventually the continuous door developed as a long open slit from top to bottom of the silo. (Figure 10) The supporting hoops as seen in wooden and concrete stave construction bridged these slits. This method became the normal practice with the exception of the Harvestore silo, which did not use doors.24 The location of the silo may seem like a commonsense decision, but in the early days of silo construction there were many contested ideas on the subject. The first square silos were built inside the barn, as it seemed the logical place to put it. If a farmer had a round barn, he usually built it in the middle and used it as a central support for the barn. Silos in the center of the barn quickly fell out of favor because it was found to be especially difficult to fill. Many farmers also believed that the heat that built up from the decaying silage could reach a high enough temperature to ignite and therefore placed the silo a safe distance from any other farm building. Over time, researchers and farmers alike reached a consensus that silos were perfectly safe and should be placed logically. The time required to move silage was greatly reduced if it was near where the cattle were actually feeding, therefore most silos came to be located directly adjacent to the barn or feedlot.
The silo and barn in close proximity has come to be the complete picture many Americans think of when imagining what a typical dairy farm looks like.25 (Figure 11) Changes in the engineering and design of their construction, as new materials and building techniques became available, led to greater size, increased efficiency, and a wider area of use. Silos were not especially attractive structures worthy of note to most people, but by 23 Ibid., 14. Rabild, Homemade Silos, 9.
Noble, “The Evolution of American Farm Silos”, 146.
24 Conner, 299. Rabild, Homemade Silos, 8.
25 J. R. McCalmont, Farm Silos (Washington D. C.: U. S. Department of Agriculture,
understanding the long process of trial and error that resulted in their current forms it is clear that silos, like buildings examined by classic architectural studies, had an equally fascinating evolution of form.
Figure 7: Monolithic concrete silo located in Oconto County, Wisconsin built in
1919. Note the dormer window and the attached ladder. This silo also features reinforcing hoops and due to the weathering of the paint, the slip form seams are now visible.
Figure 11: The typical barn and silo image most Americans think of when imagining a stereotypical farm. Located in Illinois.
Photographer: Macomb Paynes