Covered Bridge Restoration
The art of covered bridge restoration and repairing covered bridges properly is the primary means of keeping bridges in service and preserving the craft that went into building them for future generations to appreciate. The investment requires decision-makers and contractors to understand the importance of its original construction and engineering. The consideration to repair using original surviving bridge components is an important cornerstone of the National Historic Covered Bridge Preservation Program.
Covered bridges were usually constructed of timbers native to the area; the range included spruce, poplar, oak, walnut, chestnut, red cedar, and white pine. Shingles often were used for the roofs, although some builders used galvanized metal or tin. In covered bridge restoration, preserving the authenticity of each bridge requires locating the same type of timber that was originally used during their construction. That in itself can be very costly as several of these tree species have nearly vanished due to disease and urban development. Refurbishment projects often call for maximum use of original parts and that replacement parts be as close to authentic timber as possible. Some modern covered bridges, however, have glue-laminated timber, the type of wood commonly used for soaring church arches. The pieces have consistent quality throughout and can be cut into specific shapes unique to a particular bridge’s construction.
Most of the bridges that remain and continue to carry both vehicular and pedestrian traffic have undergone some covered bridge restoration and preservation work over the bridges' lifetime. Repairs have included strengthening to increase load capacity, replacement of deteriorated members, roofs, and sidings, and addition of arson prevention alarm systems in some. In a number of cases, the bridges have been re-engineered keeping only the external appearance the same.
The preference when restoring covered bridges is to keep them open for today’s vehicular traffic even though they were not designed as such. Many times this is done by keeping the external appearance but reengineering the structure. In order to truly restore a historic covered bridge, however, not only the external appearance but the engineering aspects and material integrity should be preserved, while any proposed strengthening method is complementing the original architecture. Since these structures are listed, or eligible to be listed, with the National Register of Historic Places, any strengthening methods recommended need to be in line with the Secretary of Interior’s Guidelines for the preservation of historic structures.
Covered bridge restoration may include replacing deteriorated materials, roofs, siding, or decking to strengthen the loading capacity and sustain bridge function. More intense restoration to re-engineer the truss design is sometimes required to maintain structural integrity as well as the external appearance.
Regardless of which type of wood is used, or the size of the restoration, covered bridge restoration is not cheap, nor is it quick. Restorations may range from weeks for smaller projects, to years for complete rehabilitation, which no doubt becomes a burden for local traffic. Funding can be quite difficult as well. Some bridge refurbishment funds are available through ISTEA, a federal program that provides for the enhancement of historical transportation projects.
In addition, many states have their own funding mechanisms. For example, the Pennsylvania Historical and Museum Commission give bridge preservation grants and also has set up an approval process for refurbishment projects. If not for that, inferior workmanship or people who aren’t concerned about using original materials or engineering practices would be a major concern.
In Oregon, the state lottery allocates some of its revenues to covered bridge restoration and preservation efforts. Another state, Kentucky, provides matching funds for ISTEA-allocated projects. While refurbishment is mostly viewed as a public good, this does not always translate into dollars. The general public is very interested in having covered bridges restored and refurbished, but finding the funds for a major restoration can become quite a challenge.
While some people may believe that today’s covered bridges are antique and delicate, therefore should be looked at and admired, rather than used. This is not actually true. It might seem that a covered bridge restricted to light-duty use would be in better shape than one that still bears the weight of automobiles, but that is not always correct. Better maintenance generally is given to bridges that must bear the weight of vehicles.
Much like a muscle, covered bridges have a “use it or lose it” character to them. Interestingly, covered bridges are in much better condition when they are used. With wooden bridges, the compression, tension, and flexing that come from being used keep the wood from becoming stiff and brittle; a used covered bridge stays supple and safe.
Understandably, there are plenty of fans of covered bridges. Thus, even when cities and towns are not on board with preserving them, covered bridge lovers sometimes band together to do it themselves, appealing to other fans of covered bridges to help them keep the bridges strong and standing. A list of some of the Covered Bridge Societies and Organizations can be found on this site, along with their contact information.
To read more about covered bridge restoration, you can visit:
- America's Covered Bridges - - - by Terry E. Miller and Ronald G. Knapp
- Historic American Covered Bridges - - - by American Society of Civil Engineers Brian McKee