Historic Wooden Bridges / "Covered Bridges"

Photo: Buchfaht covered bridge in Thuringia, Germany
Buchfart covered bridge, Thuringia, Germany

Project: Recording European and US wooden "Covered Bridges"

Historic "covered bridges" are rare and wonderful wooden structures found in Central Europe, Canada, the United States and parts of Asia. The "World Guide to Covered Bridges" (USA 2009) lists some 700 historic covered bridges in the USA, 150 in Canada, 160 in Switzerland and some 340 in Asia and the rest of the world. These date from the 16th. Century to the 1950s. The majority of these structures have been photographed, some have been accurately measured and documented and a rare few have been subjected to intense investigation.

Research into these structures is undertaken by various different groups, societies, institutions etc. each of which has its own particular field of interest and methods. A particularly good tool is the Dale J. Travis online database "Dale J. Travis Online Database".

The professorship Builing Documentation, Historic Building Research (Building Archaeology), Surveying at Neubrandenburg University of Applied Science has a special interest in these structures as part of providing its students with challenging structures to study. The study of these bridges includes visits, recordings, schematic drawings, models and various analysis. The project is in the early stages and began with a field trip to various 18th. century bridges in Switzerland as part of an excursion in the summer of 2002. Since then literature has been aquired, some bridges in the United States have been schematically measured (see below) and several wooden models at a scale of 1:20 completed. The production of these scale models is a permanent part of the historic building construction course in Neubrandenburg.

1. Field Trip "Grubenmann" Bridges in Switzerland

1. Grubenmann-Museum, Teufen, Canton Appenzell (CH)

2. "Grubenmann"-Bridge, b. 1780, Canton St. Gallen (CH)

2. Covered bridge models completed

1. "Grubenmann"-Bridge, Canton St. Gallen, (CH)

2. Pine-Brook Bridge, near Waitsfield, Vermont, (USA)

3. Gorham Bridge, near Proctor, Vermont (USA)

4. Ahrensberg Bridge, Mecklenburg-Vorpommern (D)

Project: National Covered Bridges Recording Project (USA) - Field Team New England

Start: Orientation program May 22-24 2003
Project: 2. June - 15. August 2003
Debriefing program: 21-22. August 2003

The Historic American Engineering Record (HAER), which is run by the National Park Service (NPS), is currently conducting a major study of America´s historic covered bridges. America has more covered bridges than any other country. Out of approximately 880 bridges surviving nationaly, HAER is documenting 50. The HAER documentation will provide written and graphic records that will aid interpretation, historic preservation and management of these historical resources, and will be transmitted to the HAER Collection at the Library of Congress

HAER will ran two Field Teams in the summer of 2003. The main field team was based at the University of Vermont (UVM) at Burlington and a second team worked out of Washington. The HAER teams were be lead by chief of HAER Eric DeLony and project leader Christopher Marston (NPS-Washington). The main field team (Vermont team) consisted of young academics and professionals from America and overseas. The overseas team members were recruited and administered by the United States chapter of the Internation Commitee on Monuments and Sites (US/ICOMOS) which runs a Summer Program covering many projects. The overseas team members (USICOMOS interns) attended an orientation program in Washington (22-24 May 2003) before starting the project. After completing the project the interns returned to Washington and take part in a debrierfing program on the 21-22 August 2003.

The Vermont team recorded seven historic covered bridges in New-England with a documentation consisting of measured and interpretive drawings, engineering analysis, historical reports and large-format photographs. The Vermont team will consisted of eight architects: Vong Dang (USA), Will Dickinson (USA), Amy James (USA), Douglas Parker (USA), Michiko Tanaka (Japan), Nadine Bauer (Germany) and Arnold Kreisel (Germany) under the supervision of Prof. Dr. Philip Caston (UK), three historians: Lola Bennett (USA), Dr. Mark Brown (USA) and Dr. Joseph Conwill (USA), four engineers: Megan Reese (USA), Rachel Sangree (USA), Francesco Lanza (Italy) and Dorottya Makay (Romania) and photographer Jet Lowe (USA). In addition each engineer called on the services of the following consultant engineers: Prof. Dr. Dario Gasparini (USA), Dr. Ben Schafer (USA), Dr. John Ochsendorf (USA) and Justin Spivey (USA).

The following seven bridges were documented in summer of 2003:

NameHAER Nr.LocationTypeResponsible
1.Taftsville BridgeVT-30Windsor County, VTMult. Kingpost truss w/archVong Dang
2.Sunday River BridgeME-69Oxford County, MEPaddleford trussWill Dickinson
3.Contoocook Railroad BridgeNH-38Merrimack County, NHTown Lattice trussAmy James
4.Sulphite Railroad BridgeNH-36Merrimack County, NHPratt deck trussArnold Kreisel
5.Shoreham Railroad BridgeVT-32Addison County, VTHowe trussNadine Bauer
6.Morgan BridgeVT-33Lamille County, VTQueenpost trussMichiko Tanaka / Douglas Parker
7.Pine Brook BridgeVT-34Washington County, VTKingpost trussPhilip Caston

During the orientation week in Washington the USICOMOS interns had the chance to meet each other, to learn about the preservation system in the United States and see some of Washingtons most interesting monuments.

USICOMOS interns outing in Washington.Offices of the NPS, Washington - Interns and members of staff

On the last day the Vermont team interns finally got to meet the Washington staff of the NPS and those who would be working with them on the historic covered bridges.

In the first project week in Vermont the complete team were invited to the "Covered Bridge Preservation National Best Practices Conference" held at the UVM.

During the second project week work started on measuring and drawing the individual bridges. Two bridges illustrate the diversity of types and conditions of the structures being measured. Pine Brook Bridge in Washington County, Vermont was built in 1873 and is one of four remaining "Kingpost" truss bridges in Vermont.

Pine Brook Bridge, Vermont.Pine Brook Bridge, Vermont.
Pine Brook Bridge, Vermont.Pine Brook Bridge, Vermont.

The 48´7" span was restored in 1976. The bottom chords have beem modified and the whole bridge was lifted 18 inches to avoid spring floods. In addition two steel joists were inserted under the floor deck as safety precaution. They are placed such that they only carry any loads when excessive deflection of the deck occurs.

The Sulphite Railroad Bridge in Merrimack County, New Hampshire was built in 1896. It is also known as the "Upside Down Bridge" because the railroad track runs over the roof rather than through the structure. It is the only surviving deck-type covered bridge in the United States. It was set on fire by arsonists in October 1980. Despite the outer quarter of an inch of the wooden members being chared, the structure is still able to support itself.

Sulphite Bridge, New Hampshire.Sulphite Bridge, New Hampshire.
Sulphite Bridge, New Hampshire.Sulphite Bridge, New Hampshire.

In addition to the HAER bridges being documented several other interesting bridges were documented. One was Comstock Bridge in the vicinity of the Canadian border (by the town of Montgomery). This bridge was built in 1883 by S. and S. Jewett. The 68´10" span is a simple town lattice truss. Interesting is the fact that it has a positive camber, which is not often seen.

Comstock Bridge, Vermont.Comstock Bridge, Vermont.
Comstock Bridge, Vermont.Comstock Bridge, Vermont.

The bridge was being restored by the Vermont Agency of Transportation. The photo´s here were taken on the 22nd of June 2003. The cladding has been removed prior to dismanteling the structure and moving the trusses to the river bank for overhaul. We managed to measure the camber and the position of many of the joints in order to ascertain how the camber was achieved.

On revisiting the bridge on the 29th of July 2003 it was found that the bridge had already been dismanteled and removed from the river.

Comstock Bridge, Vermont.Comstock Bridge, Vermont.
Comstock Bridge, Vermont.Comstock Bridge, Vermont.

The abutments will be rebuilt as their bridge bearing surfaces were found not to be level, which had caused a twist in the two trusses. The trusses are laid horizontaly by the roadside leading to the bridge. Only those individual members that are beyond repair are being replaced. This is mainly at both ends where rot has set in due to rainwater being trapped between the bridge and the abutments. Where possible the original treenails remain undisturbed in their holes. However a number of replacements are necessary where movement in the bridge has worn them or new members are being inserted. The new holes are drilled with several different types of bit including original 19th century augers modifyed to fit contemporary electric drills.

Several further bridges are currently being restored in Vermont. One is the Gorham or Goodnough Bridge on the Pittsford-Proctor town line crossing the Otter Creek. It was originaly built in 1841 or 1842 by Abraham Owen and Nicholas Powers and is roughly 115 feet long. This is not the first time that the bridge has been removed from its abutments. Following the flood of 1927 the bridge was washed away and remained in Otter Creek untill the fall of the following year. The rebuilding was finally completed in 1929.

The bridge has been removed as a complete structure in one piece from the abutments and set down in a field near the river bank.

Gorham Bridge, Vermont.Gorham Bridge, Vermont.
Gorham Bridge, Vermont.Gorham Bridge, Vermont.

It is supported by four crossbeams which are in turn supported on tressels allowing repairs to be carried out on all sides, top and bottom. The bottom chords have to be completely replaced.

More news and further information on Vermont´s covered bridges can be found at the "Vermont Covered Bridge Society´s website".

4. Inventory of Germany´s historic covered bridges
(Deutschlands erhaltene historische gedeckte Holzbrücken - Ein Inventar)

There are some 70 historic covered bridges in Germany. Some are famous, such as the Rheinbridge at Bad Säckingen (GPS: UTM 32T 421113 m E 5266978 m N) which has the longest covered bridge main structure at just over 200 m in Germany and possibly in Europe. It is also Germanys southernmost covered bridge and probably has some of the oldest timbers still in use in a bridge. The bridge belongs to the German town of Bad Säckingen, but it crosses the border into Switzerland at the deepest part of the river. It has been restored many times and used to carry motor vehicles - now it is a pedestrian footbridge.

Bad Säckingen, Baden-Württemberg (March 2005).Bad Säckingen, Baden-Württemberg (August 2005).
Bad Säckingen, Baden-Württemberg (March 2005).Bad Säckingen, Baden-Württemberg (August 2005).

Others are only locally known. Germany´s most northern covered bridge is the Wildhof covered bridge over the Kammerkanal (Obere Havel-Wasser-Straße) near Ahrensberg (GPS: UTM 33U 368479 m E 5901671 m N). It uses the Town truss design imported from the United States. The bridge was built in 1928, but had to be overhauled following the end of the second world war. By 1995 the deck and lower chords had reached a negative camber of 12 cm. In that year two RSJs were added to support the floor. The 16.6 m long bridge is due to be overhauled in the next few years.

Ahrensberg, Mecklenburg-Vorpommern (March 2007).Ahrensberg, Mecklenburg-Vorpommern (March 2007).
Ahrensberg, Mecklenburg-Vorpommern (March 2007).Ahrensberg, Mecklenburg-Vorpommern (March 2007).

Another famous German covered bridge is in the town of Forbach (GPS: UTM 32U 452984 m E 5391832 m N). The 37.8 m free span between the butresses is probably the longest or second longest of the remaining covered bridges in Germany. The bridge in its visible form has been here since 1778. In 1955 the original late 18th century wooden frame was replaced with the current one. Although the replica duplicates the general design of he original, it differs in detail especially in the use of steel bolts and plates. At over 50 years old it has itself become a historic monument in its own right and documents building convervation theory and practice in post war Germany. In 1976 the roof was covered with red cedar singles imported from British Columbia, Canada.

Forbach, Baden-Württemberg (March 2005).Forbach, Baden-Württemberg (March 2005).
Forbach, Baden-Württemberg (March 2005).Forbach, Baden-Württemberg (March 2005).

This 72 m long covered bridge in Wünschendorf, Thuringia (GPS: UTM 33U 294946 m E 5631039 m N) still retains its original wooden trusses despite being renovated in 1998. The main timbers are 40 cm thick. The bridge is dated 1786 and is still open to motor traffic.

Wünschendorf, Thuringia (Juni 2007).Wünschendorf, Thuringia (Juni 2007).
Wünschendorf, Thuringia (Juni 2007).Wünschendorf, Thuringia (Juni 2007).

The inventory of Germanys remaining wooden covered bridges, which includes general and detail photographs, basic dimensions, historical data and GPS loction coordinates, is available to purchace (Caston, Philip: Germany's Remaining Historic Wooden Covered Bridges [Series J, Volume 7 Neubrandenburg University of Applied Sciences publication], Neubrandenburg 2010 (ISBN: 978-3-932227-89-9).

To order your copy (10,- € + pp) please contact the Neubrandenburg University of Applied Sciences Marketing and Communications department at: presse@hs-nb.de

5. The Third China International Symposium on the Roofed Bridges of Wooden Arch Structure (in Pingnan County)

The Third China International Symposium on the Roofed Bridges of Wooden Arched Structure held in Pingnan, Fujian, China between the 15th. and 18th. October 2009 was a good venue to learn about Chinese covered bridges and to explain to an international audience some of Germany´s historic covered bridges. The arrival day was crowned by an evening visit to the local opera with traditional and modern Chinese pieces performed by the local ensemble.

The offical opening ceremony took place on the morning of the 16th. October and was held jointly with a celebration ceremony of the Inscription of the Traditional Design and Practices for Building Chinese Wooden Arch Bridges onto the "list of Intangible Cultural Heritage in Need of Urgent Safeguarding by UNESCO". Lecture sessions followed (in Chinese) and included three lectures in English; Cultural Aspects of Wooden Bridge Design (Tom F. Peters); In Search of China´s Historic Bridges (Ronald G. Knapp); Germany´s Oldest Wooden Covered Bridges (Philip S. C. Caston).

Lectures and presentations continued in the morning of the 17th. October. In the afternoon there was a group visit to Wan´an covered bridge. Following the visits, bridge builder Mr. Chuncai Huang demonstrated how a wooden arched bridge is assembled (in model form) in Pingnan Cultural Center.The morning of the final day (18th. October) involved group discussions and a conference summary before another group visit to Qiancheng covered bridge. Further bridges in the vicinity were also visited after the official end of conference.

Pingnan town with its cinema decorated for the conference.Opening ceremony held in Pingnan cinema.
Pingnan Cultural Center with covered bridge model exhibition.Load test of wooden arch.

There is still much research to be done in locating and compiling the history of China´s covered bridges. Much emphasis has been placed on the "woven arched" covered bridges, but there are many other historic forms such as "beam and cantilevered supports" which need to be quantified. It seems the same problems as found in Europe and North America beset Chinese covered bridges. Recently Baixiang covered bridge was lost to fire, others are in a desolate condition, others renewed with a loss of original material, some ancient examples are (as far as is known) however in their original condition. One particulary romantic bridge is the Guangli covered bridge (GPS: UTM 50R 695009 m E 2996354 m N) 18 km north of Pingnan. It could well be several hundred years old and is still in use for pedestrian and bicycle traffic.

Guangli bridge near Pingnan, Fujian province (October 2009).View from Guangli bridge, Fujian province (October 2009).
Guangli bridge near Pingnan, Fujian province (October 2009).Guangli bridge near Pingnan, Fujian province (0ctober 2009).

Pingnan county´s most famous bridge is the Wan´an covered bridge (GPS: UTM 50R 683326 m E 2968145 m N), 17 km south-west of Pingnan. The bridge is 98.2 m long and spans a wide river with six arches. Ron Knapp´s research into the bridge (Knapp, Ronald G.: Chinese Bridges, 2008, Pg. 240-241) has revealed that it was destroyed many times. Follwing a tragic fire the bridge was rebuilt in 1932. Flood damage destroyed nearly one third of the structure in 1952. The bridge was reconstructed in its present form in 1954.

Wan´an bridge near Pingnan, Fujian province (October 2009).Wan´an bridge near Pingnan, Fujian province (October 2009).
Wan´an bridge near Pingnan, Fujian province (October 2009).Wan´an bridge near Pingnan, Fujian province (October 2009).

There are probably many hundreds of beam and cantilevered support covered bridges all over China that need documenting. This is the Baogong covered bridge (GPS: UTM 50R 693509 m E 2975555 m N) on the road to Wan´an bridge, ca. 4.5 km south-west of Pingnan. The small free span negates the need for a woven arch. The roof and walls are of the same basic construction as found in the arched bridges. The free span of the beam floor is reduced by cantilevering the first supports out over the river.

Baogong bridge near Pingnan, Fujian province (October 2009).Baogong bridge near Pingnan, Fujian province (October 2009).
Baogong bridge near Pingnan, Fujian province (October 2009).Baogong bridge near Pingnan, Fujian province (October 2009).

6. Books and articles published by Philip Caston on the subject

Doing it the American way - Federal historic building recording in the United States In: Kresse, W. (Ed.): Forschung und Praxis - Arbeitsberichte aus dem Fachbereich Bauingenieur- und Vermessungswesen der Fachhochschule Neubrandenburg und befreundeter Institutionen, Neubrandeburg 2005 (S. 63ff).

Historic Wooden Covered Bridge Trusses in Germany In: Kurrer, E-K. u. a. (Ed.): Proceedings of the Third International Congress on Construction History, Berlin 2009, S. 329-336.

Germany's Oldest Wooden Covered Bridges In: Proceedings of the Third China International Symposium on the Roofed Bridges of Wooden Arch Structure in Pingnan County, Pingnan (P.R. China) 2009, S. 44-64.

Germany's Remaining Historic Wooden Covered Bridges / Deutschlands erhaltene historische gedeckte Holzbrücken, Neubrandenburg 2010.

Historische überdachte Holzbrücken in Deutschland In: Koldewey-Gesellschaft - Bericht über die 45. Tagung für Ausgrabungswissenschaft und Bauforschung, Dresden 2010, S. 287-296.

Wie Lange ist die Rheinbrücke in Bad Säckingen? In: Teschke, Gerd (Hrsg.): Freiraum und Geodäsie - Ein Berufsleben im Dienste exakter Daten - Herrn Prof. Dipl.-Ing. Rolf-Werner Rebenstorf gewidmet (Schriftenreihe J, Band 8 der Hochschule Neubrandenburg), Neubrandenburg 2010, S. 71-98.

The Use of the Polygonal Arched and Strutted Framed Truss in German Wooden Bridges 1500-1850 In: Bayerische Gesellschaft für Unterwasserarchäologie (Hrsg.): Archäologie der Brücken. Vorgeschichte. Antike. Mittelalter. Neuzeit, Regensbug 2011, S. 294-298.

Kronachs historische gedeckte Holzbrücken In: Cranach, Nr 42, 21. Jahrgang, Kronach 2011, S. 9-13.

Germany's Surviving 19th Century Historic Wooden Covered Bridges In: Proceedings of the fourth International Symposium of Covered Bridges (Wooden Arched Structure) of China in Qingyuan, Qingyuan (V.R. China) 2011, S. 11-35.

E-Mail caston@hs-nb.de

Homepage Prof. Dr. Philip Caston

Homepage Hochschule Neubrandenburg

Letzte Änderung 11.07.2011