This page last updated September 14, 2008, 6:33 AM
There are many romantics who love the days gone by and the simpler life. These people talk about their heritage, especially about covered-wooden bridges as a way to return to less hectic times. The covered bridges provided a way of crossing a body of water with protection from rain and snow. They were the original tunnel of love during a ride in a buggy or sled.
The covered bridge was used by more than one local boy when he puffed his first cigarette, and evil doers sometimes lurked in the shadows of the bridge. The covered bridges were generally a triumph of local engineering. As the historic structures are given a helping hand by generous individuals and organizations, preservation takes place from the ravages of replacement, abandonment, vandalism, and arson.
Most of the original and surviving covered bridges crossed streams with a single span. The first crossings of the major rivers of our Commonwealth were accomplished with multiple-span covered bridges. The longest of these was 5,690 feet, erected across the Susquehanna between Columbia and Wrightsville. The closeness of covered bridges to water resulted in accelerated deterioration due to rot, as well as ever-present danger from floods.
The exceptional work of the Columbia County Covered Bridge Association is shown in the Columbia-Montour Tourists Bureau brochure on covered bridges which you can find here. Here are two examples...
The Shoemaker Covered Bridge
The rehabilitation of the Shoemaker covered bridge (PA-19-06) has been under way by the state and is now completed. The bridge will be turned over to the Columbia County Covered Bridges Association within the next couple of weeks and that group will then be responsible for its maintenance.
The Shoemaker Covered Bridge was built in 1881 by T.S. Christian for $322 and named for a nearby farmer and lumberman, Joseph Shoemaker. The Bridge is Queenpost constructed and is 48 feet long and 14 feet wide. From Iola, head west on Route 442 for about a mile, then turn left on Route 621, Chestnut Lane. The bridge spans West Branch Run northwest of Iola. The stream eventually flows into Little Fishing Creek in Pine Township, and is near Pennsylvania Route 442, northwest of Iola, Go here to see the condition of the bridge in the past.
The West Paden Covered Bridge
Work on the abutments of the West Paden Bridge (PA-19-12), which was destroyed by the “No-name Flood of ‘06," has been completed. The Burr trusses, which have been under construction along the side of the East Paden Bridge,were placed into position on the abutments September 11, 2008, starting at 9 AM. West Paden is half of what is commonly known as the Twin Bridges. West Paden is a Burr Arch bridge.
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A crane gently sets the truss in place. |
There are many similarities among covered bridges, but like Holsteins in a field, you'll never find two exactly alike. None has had identical care and maintenance. Log or corduroy bridges were the first miserable, bone-banging attempts to ford a stream of water. The fragments of records of these early bridges that are still available categorize them as unhewn trunks of trees of unequal sizes laid loosely across pieces of timber placed lengthways. When the trees became too heavily laden or rotten, they sometimes kerplunked into the streams sending horses and carriages into the water.
Experience showed early builders that perpendicular trusses high across the roadbed on either side strengthened the bridge until rot and weather weakened the trusses. Plank housings protected them although wind pressure in heavy storms "played hob," as Father used to say, with the roadbeds and pilings. Transverse braces helped and roofing to keep rain and snow off the roadway plankings also helped. Eventually, roofs over a covered bridge became an effective timber-preserving measure.
A typical covered bridge like either the Shoemaker or the Wast Paden covered bridge uses heavy timber trusses to carry the load. The floor system runs between the longitudinal trusses and distributes the loads between those trusses. The final touch of the bridge is lateral bracing, a wall system, and the roof. A bridge engineer would call this style of structure a "through truss."
The newly constructed abutments for the "reconstituted" West Paden bridge now hold wooden beams which will be the centerpiece of the new bridge. The $632,570 project is being financed using funds from the Federal Emergency Management Agency following the loss of the original structure in the "no-name" storm of 2006. Pictures of Thursday's activities will be posted at http://coveredbridges.org/photos.html.
The series of covered bridges from Elk Grove to where Fishing Creek flowed into the Susquehanna were generally built to accommodate a single lane of traffic, although there was one double bridge in the state of Pennsylvania at the time of its demolition known as the "double-track" bridge over Fishing creek in the town of Bloomsburg. .
This bridge had a separate roadway for east-bound and west-bound traffic. For eighty-three years the Double Track bridge spanned Fishing creek at the lower end of Bloomsburg. That bridge came along in 1840--the year of "Tippecanoe and Tyler, too." The entire bridge was constructed for $2,150. For more information on the double-track bridge, refer to the Benton News archives for September, 2006, and for more information on the six remaining twin-covered bridges remaining consult World Guide to Covered Bridges, published by the National Society for the Preservation of Covered Bridges, 1989 edition.
Most covered bridges were constructed at narrow places in the stream and always at right angles to the flow of the water in order to keep the span length as short as possible. Horses and carriages had no problem making the 45° turns so often found at the end of bridges, but for modern traffic the sharp curves proved to be both a blessing and curse. The bridges became functionally obsolete, but many bridges are standing today because of this basic design. The sharp curves limited the amount of load that could cross the bridge. A load of hay or straw piled high was simply out of the question. It slowed up vehicles when they approached the bridge, since it was usually unknown if a vehicle was in the bridge until the vehicle "nosed" into the dark confines of the covered bridge. It was not uncommon to find a young couple spending time with their horse and carriage on the bridge. The slow speed at which the bridge was entered reduced the number of accidents which could have had an adverse affect on the bridge. What worked for the horse-drawn vehicle was not acceptable for modern cars and trucks.
A double whammy in this regard took place at the two covered bridges which over the years have spanned the water around Grassmere. The first one, known as the Laubach Bridge, washed out in the storm of 1848 commonly called the "Great Freshet." The second Grassmere bridge, known as the Welle Hess bridge, collapsed from the weight of an overloaded oil truck.
Pennsylvania history is full of stories of covered bridges "going into the drink." In 1896, the Catawissa-covered bridge blew down. In 1866, the covered bridge over the Lackawanna River at 9th Street in Honesdale dropped. A tramp burned a bridge by accident as he tried to keep warm in Stroudsburg. In March 1919, the covered bridge over the Susquehanna at Shickshinny burned in a 45-minute fireball. In Media, Pennsylvania, an eight-ton steam roller dropped 25 feet through the floor decking into Crum Creek in 1905.
It would be nice to claim the idea of creating covered bridges as our own idea, but actually the concept came from central Europe. The Kapellbrücke (meaning "chapel bridge") crosses the Reuss River in the city of Lucerne, Switzerland. The bridge is the oldest covered bridge in Europe, built in 1333.
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| The 670 foot Kapellbrücke bridge in Switzerland was designed to help protect the city of Lucerne from attacks. The bridge was partially destroyed in a 1993 fire, but was quickly rebuilt. The bridge and an adjacent Wasserturm (Water Tower) are trademarks of the city of Lucerne. Photo courtesy of Dale Ruckle, Plano, Texas. | ||
Covered bridges can be found in all well-forested countries. Bridges generally were made of wood in order to keep the structure well protected and to prolong its life.
The first known covered bridge in our country was built between 1797 and 1804 in Philadelphia when 550 feet of a 1,300-foot bridge were covered.
Some of the early covered bridges were a form of a truss bridge known as a lattice bridge. This type of bridge was patented as a "Town Lattice Truss." Our state has twenty of these bridges remaining. The town lattice was replaced by the Howe Truss which used lighter timbers, a wider lattice, and cast-iron tension-members, rods that ran through the support timbers. Nuts were attached to the threaded ends so that a sagging bridge could be lifted and "trued" easily. The Theodore Burr Covered Bridge Society of Pennsylvania discusses all types of construction here. According to the Society, only five Howe-truss bridges remain in Pennsylvania.
We'll slow down to remind you that a covered-bridge truss system is assembled in some shape that includes a triangle, since the triangle is the only two-dimensional figure that won't become distorted under stress. Early builders worried about bridge stability. A covered bridge dating to 1836 in Traxville, Snyder County, carried the following notice: "For riding, driving, or leading or causing to be driven or led, any horse or beast of burden faster than a walk not less than $5 nor more than $30. For carrying fire across the bridge except it be secured in a vessel or lantern, five dollars."
Whatever the style of construction, the longitudinal trusses are the backbone of a covered bridge in whatever configuration it is used. The primary trusses of a covered bridge contain a top chord, a bottom chord, and web members. A beam has strength from its resistance from bending. The bridge is pulled and tugged by forces of compression and tension, especially on the "chords," the term applied to the members running longitudinally along the top and bottom of the truss. Chord members in a truss are often spliced and assembled in multiple pieces. The splices on the chords of the "reconstituted" West Paden bridge are easily visible.
All the vertical and diagonal truss members between the upper and lower chords that keep the chords from moving relative to each other are called "web members." These are what transfer vertical loads along the span to the supports at the ends. These members are always in stress, either pulling or tugging. Here, too, are components with special names: the diagonal members are "end post," "main diagonal," "counter" or "brace." The vertical elements are called "posts" or "verticals." The portion of the truss between verticals and diagonals is called a "panel." If you would like to know more about the other terms which apply to a covered bridge, visit the Burr web page which explains terms.
Now that you know so much about covered bridges, download an application for membership in the Burr Society here.
As reconstruction of the West Paden bridge continues using modern-construction equipment, it is easy to lose track of the time it took to build our original covered bridges. There is little documentation of the building of the original bridges. We suspect that after years of talking about the need for a bridge to ford a creek, someone simply stood up and took on the task. In some cases, the local government stood behind the cost. In some cases, the financing was privately arranged and crossing of the bridge after construction required the paying of a toll. An example of this was a covered bridge at Douglassville, Pennsylvania, when in October 1884 the citizens of Amity, Union and Douglas townships met with the intent of making the stock-company bridge crossing the Schuylkill at Douglassville into a county bridge with no fees for crossing. The bridge had operated through a stock company for forty years. In any event, financing had to be arranged.
When the issue of financing has been solved, it was time to find a competent builder. There were men like Theodore Burr (1771-1822 or 1824), a "builder of eminence," as Poulson's American Daily Advertiser described him. Burr was a bridge builder who completed a bridge over the Mohawk at Schenectady, another in the Catskills, one over the Hudson north of Albany. In our state, his bridges crossed the Susquehanna at Nescopeck Falls (Berwick), Columbia, Harrisburg, and Northumberland. His last bridge was 4,170 foot long over the Susquehanna River in Maryland. Somehow, building a 130-foot span over Fishing Creek didn't seem like it would have been a challenge for him!
The Berks and Schuylkill newspaper of November 13, 1824, published an advertisement which, in part, read as follows: "The President, Managers and Company of the Centre Turnpike Road, leading from Reading to Sunbury, having resolved to erect a new bridge over the Little Schuylkill River, at the place where the present bridge is located near Schuylkill Forge in Schuylkill county." The specifications, frankly, lacked specificity! "The bridge is to be of wood, either of one or two arches, according as can be agreed upon, with stone abutments and pier (if a pier shall be necessary) of the width and length of the present bridge. The whole is to be substantially built and covered with a good shingle roof, and is to have proper guard rails on each side. It will also be expected that the building will be commenced as early in the spring as the season will permit, and finished with as little delay as possible." How many present-day contractors do you know who would love to build under those conditions?
The streams in our area were generally not large enough to warrant builders like Burr or probably even to advertise to find a builder. Many who ended up building covered bridges were ordinary farmers with a minimum of logging background--but no prior experience at bridge building. As a testimonial to their engineering ability, a number of these bridges have endured for well over a century.
In the actual construction process, the abutments--the facewall, backwall, and wingwalls--came first. The abutments support the bridge at each shore of a stream. A Pennsylvania newspaper, the Weekly Patriot and Union published in its edition of July 4, 1867, that stone masons were at work on the new piers of a covered bridge. According to the article, the island was "covered with heavy timber for the body of the bridge."
Most abutments took the form of cribwork. Squared logs often came first followed by a layer of either flat rocks or horizontal logs. Any cracks or openings were filled with small stones. As the sheer weight of the bridge and its traffic bore down on the cribbing, the logs and stones were firmly held in place. If a pier was needed in the center of the creek to support more than one span, the same sort of cribwork was constructed around that pier. Wooden cofferdams were sunk in the water if the stream was deep. Concrete was poured into the forms.
The ramps to the bridges abruptly maneuvered in a 45° angle from the general direction of the road to the decking on the bridge. The ramps were stone filled, and often flanked by large, flat rocks or by timbers which gently guided the users onto the bridge. During the time that the ramps were being built, timbers were cut in local sawmills. Horse-drawn teams hauled building materials of wood and stone to a staging area near the bridge. The timber trusses for the sides of the bridge were laid out nearby, then assembled and marked, much as was done with the current West Paden bridge reconstruction. The truss timbers were disassembled prior to the actual construction.
First to be moved to the abutments was the heavy base of the bridge. These "lower chords" curved slightly upward to accomodate the weight of the bridge and its load as it settled on them. Finally the day came, a day somewhat akin to an Amish barn raising, when all able-bodied men and their teams and their ropes and their pullies convened for the purpose of sliding the chords from the near abutment to the far abutment. The chords rested on blocks of wood which actually carried the weight of the superstructure and the traffic. Cross bracing reinforced the bridge though heavy-floor beams with stringers laid lengthwise over them. A sub floor of diagonal boards came next with the deck planking on top laid lengthways.
The prefabricated side trusses came next as they were slid across the deck and raised with teams and pullies in a fashion similar to the raising of the side of a barn. In fact, generally that was the experience that the farmer/bridge builder had: he raised the side of the bridge as he raised the side of his own barn. Every drop of experience that he had from raising barns was needed to tackle the building of a covered bridge. Look at the side of a covered bridge and the side of a barn today and you'll see what we mean.
Covered bridges use both treenails and regular nails to build the bridge. "Treenails" or trunnels, as they were commonly pronounced, were cylindrical wooden pins used in fastening the parts of covered bridges together. They were used in timber-frame construction and wooden shipbuilding. Covered bridges as well as the shipbuilding industry often used trunnels as fasteners. Many local barns and covered bridges have their trunnels clearly visible. The wood trunnels expanded as they came into contact with water. The more water, the tighter the trunnels gripped the planks of a bridge.
The trusses of covered bridges were assembled slowly piece by piece starting with the bottom chords. Then came the diagonals, counter braces and top chords. The rafters and the roof came last.
The exterior sheeting was generally mounted vertically. Windows served a number of uses in a covered bridge, although as a building took on some age the openings between the vertical boards allowed more and more light into the interior. As horses and carriages phased out and automobiles began using the bridges, the windows were needed to see if anyone was in the bridge before entering from the right-angle ramp.
Wood eventually wears out even if protected from the elements. Many covered bridges were replaced with iron and concrete after a gully washer. If nothing devastating happened to a covered bridge, little maintenance was required or given. Paint was neither needed nor used.
What was the longest covered bridge in the world, you ask? Canada's Hartland Bridge is 1,282 feet long. It originally opened for business 107 years ago. The bridge dates from 1898 as a toll bridge and uses seven Howe truss spans for the Heartland Bridge Company.
Our area is fortunate to have many people who wish to preserve the past and protect the proud wooden structures still remaining in our county. Whether you think that a covered bridge is simply "something out of the past" or "something to preserve" from our past does not matter. What is important is that an important legacy will be available for future generations.
