Cornish-Windsor Covered Bridge
Site: N08-5 / V09-61
National Register Nomination Information:
Present Physical Appearance:
The bridge consists of two spans supported by two flanking timber lattice trusses adapted from the Town patent design. The trusses are built of six-by-eight inch spruce timbers which are bolted together at intervals of four feet into the diagonal Town lattice pattern. Each truss has two upper and two lower multi-segmented chords bolted to the lattice members. Some joints in the chords have been reinforced with steel plates. Iron rods extend from the tops of the trusses to the abutments and pier to anchor tile bridge.
Two sets of upper lateral bracing extend between the trusses. One set forms crosses within the top beams; the other set connects the top chords, with iron reinforcing rods extending through the apexes formed by adjoining crosses. Wood struts provide additional reinforcement between the upper intermediate chords and the top beams. The lower lateral bracing forms crosses between the bottom chords, with iron reinforcing rods extending through the apexes of adjoining crosses.
The massive west abutment and central pier of the bridge are built of stone blocks mortared together. The east abutment is completely faced with concrete. The west abutment has some concrete facing on the north side at water level. The extreme ends of the trusses rest on secondary abutments which are recessed behind the primary abutments and built of irregular stone slabs laid dry. Wing walls also built of stone blocks extend upstream from both abutments. The central pier is rounded on the north (upstream) side and flares outward toward the river bed to deflect floating debris and ice.
The bridge is 450.5 feet long at floor level. The gable ends overhang the roadway six feet at the east portal and eight feet at the west portal. Hence along the ridge the bridge is about 465 feet long. The pier stands nearly under the midpoint of the bridge: the two clear spans measure 204.6 feet and 203.7 feet respectively east and west.(1) The wood floor begins 1.5 feet inside the east portal and 3.5 feet inside the west portal; the approaches are paved. The floor (and road surface) consists of planks laid flat and parallel to the trusses. The overall width of the bridge is 23.5 feet. The roadway is 19.5 feet wide, which allows two-way vehicular traffic through the bridge. The posted legal load limit is six tons.
On the exterior, the trusses (and sidewalls) of the bridge are sheathed with matched are hung vertically and painted grey. Eighteen small square windows with hoods are cut at regular intervals in each side wall of the bridge. The windows in one wall are spaced diagonally opposite those in the other wall. Vertical matched boards, which are painted white for increased visibility, protect the ends of the trusses immediately inside the portals. The gable ends, which are also painted white, are sheathed with horizontal clapboards. The portal openings are framed with semi-elliptical arches.
A medium-pitch gable roof covers the entire bridge; it does not overhang the gable ends. The roof is framed with light rafters, which extend from the top chords to abut at the ridge. There is no internal bracing connected to the roof structure. The roof is covered with corrugated metal sheeting.
The Cornish-Windsor Bridge has the numbers (New Hampshire) 29-10-09 and (Vermont) 45-14-14 in the World Guide to Covered Bridges published by the National Society for the Preservation of Covered Bridges. The number assigned to the bridge by the New Hampshire Department of Public Works and Highways is 064-108; the number assigned by the New Hampshire Department of Resources and Economic Development is 20.
Original Physical Appearance:
Tasker, who was an intuitive engineer able neither to read nor to write, directed the work.(2) He used an adaptation of the Town lattice truss, substituting six-by-eight inch timbers for the usual planks in the lattices. The structure was framed initially in a Windsor meadow to the northwest of the site.(3) Construction took about seven months; the bridge was opened to traffic probably in late October or early November of 1866
The Cornish-Windsor Bridge has survived several major floods to become the longest covered wood bridge remaining in the United States.(7) The bridge has an overall length at floor level of 450 5 feet. The longer of its two spans has a clear span of 204.6 feet, only 5.4 feet shorter than the longest wood clear span in the world - the 210-foot span of the Old Blenheim Covered Bridge at North Blenheim, New York.(8)
The Cornish-Windsor Bridge remains essentially original in structure, lacking any of the various devices added to many other covered bridges for reinforcement. The bridge continues to carry two-way traffic restricted only by the current legal load limit of six tons. In 1970 the American Society of Civil Engineers designated the bridge as a National Historic Civil Engineering Landmark.
Allen, Richard Sanders. Covered Bridges of the Northeast. Brattleboro VT: The Stephen Greene Press, 1957.
Allen, Richard Sanders. Rare Old Covered Bridges of Windsor County. Brattleboro VT: The Stephen Greene Press, 1962.
Congdon, Herbert Wheaton. The Covered Bridge. Middlebury, VT: Vermont Books, 1970.
Dana, Richard T., The Bridge at Windsor, Vermont and Its Economic Implications. New York: Codex Book Co., 1926.
Foster, Margaret. "The Windsor-Cornish Bridge, Lebanon, NH: Dartmouth- Lake Sunapee Region Association, n.d.
DATE ENTERED: November 21, 1976
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