Location: The Guelph Bridge
There is a long history of covered bridges in North America, dating from the 19th century to the present. In earlier times, wood and labour were readily available, so it made sense to bring these two resources together to span small and mighty rivers. Like all wood structures, if you can manage the elements, particularly rain, wooden bridges will last an extremely long time.
The problem of long spans was solved in 1840 with the invention of the “Howe Truss,” which integrated an iron tension rod. New Brunswick was home to the longest such bridge in the world with six spans extending over 1,282 feet. Alas, it is being taken down this summer, not as a result of structural failure, but because they could not find shingles to match those blown off during recent storms. Fortunately, over fifty covered bridges remain in the province today. The kissing bridges, as they are often known, remain a pillar of New Brunswick tourism.
Closer to my home near Kitchener-Waterloo, Ontario, the West Montrose Bridge is the oldest in Canada, dating from 1880. Just in case the 198 foot (60 metre) span isn’t impressive enough, the visual impact has been increased by painting the cladding bright red. Guelph was reminded of the importance of this landmark in 1992 when it was designated by Ontario’s Archaeological and Historic Sites Board, and chosen as the site for a Timber Framers Guild conference. In celebration, 400 timber framers collaborated to build a pedestrian bridge spanning 132 feet in five days.
The conference organizers chose a pair of giant “town lattice trusses” as the primary structure, since they can be fabricated fairly easily. This also enabled each attendee at the conference to sign and drive a peg into one of the joints of the lumber formed the trusses. The bridge contains over 50,000 board feet of lumber, approximately 30,000 in the trusses alone, or enough for four or five houses. The trusses are constructed of Douglas Fir, except for two large posts that were milled from a willow tree that had been cut down to make way for one of the bridge abutments. The posts stand as a small recognition of the fact that these behemoths were traditionally built from local trees. Now we earn environmental benefits from sourcing materials for our projects close to home.
Timber framing is a distinctive style of building construction in which heavy timbers frame the structure instead of slender dimensional lumber. One of its most defining elements is its unique joinery. Like furniture, heavy timber is joined together via mortises and tenons, then secured by wooden pegs. Approximately forty years ago, craftsman revived the timber framing tradition and ushered the design style into the modern vocabulary. Similar to those erected in 1840, newer hybrid structures resolve the inconvenient stresses on connections using steel concealed within the joints.
Unlike much of current construction, there is an opportunity for a social aspect to timber framing. All of the structural timbers of a building are prepared ahead of time. Then a community can come together to assemble the pieces and hand-raise the structure using historically authentic frames, pike poles, ropes and people power. The construction of the Guelph Bridge required over 21,000 hours of labour and after it was done, I can attest that the celebration was well worth attending.
Don’t take my word for it. The process is wonderfully described in a YouTube video: https://www.youtube.com/watch?v=YnRtuAf0GGQ.
SUBCONSULTANT TEAM:
Fire Tower Engineered Timber / Hamill Creek Timber Homes / Heritage Natural Finishes / City of Guelph Economic Development / Montana reclaimed Lumber Company / Hardwick Post & Beam