Why are covered bridges covered?

Dear Cecil:

Not to ask a stupid question, but … why are covered bridges covered? It can't have been just because they look good that way in the postcards.

Cecil replies:

Why not? Looking good has always been prized over functionality in our society. Consider the thong bikini. But you were asking about bridges. You realize, first of all, that covered bridges are wooden. Excuse me if I spell this out in excessive detail, but these days one can leave nothing to chance. The uninformed believe covered bridges are covered to protect the wooden flooring from snow. Ha! Who cares about the flooring? Flooring is cheap. (Except when it’s in your kitchen, I mean, but that’s a paradox we’ll take up another day.) Truth is, one of the jobs of a bridge tender in the old days was spreading snow on the floor of a covered bridge in winter so sleighs could get across. A few characters say the bridges were covered to prevent horses from getting spooked when they realized they were above flowing water, but about this theory we will not even speak.

What you’re really trying to protect in a covered bridge are the structural members — the trusses. Made of heavy timber, these are the expensive part of the bridge, and if they fall apart due to exposure to the elements, so does the bridge. An unprotected wooden bridge will last maybe ten years. Put a cover over it, however, and it’ll last for centuries. Or at least until some birdbrain adolescent decides to burn it down, the fate of quite a few covered bridges in recent years. But I digress.

Covering a wooden bridge is easy. The trusses already form a boxlike framework. Tack on some rafters and shingles and siding, and there you go. OK, it’s not brain surgery, but somebody had to think it up, and the somebody usually credited is Timothy Palmer, who built the prototypical American covered bridge in Philadelphia between 1800 and 1804. Over time there have been anywhere from 3,000 to 16,000, depending on who’s doing the estimating. Today fewer than 800 remain. Be assured, however, that this dwindling number is the result of progress, heavy trucks, and teenagers, not exposure to the rain.

Send questions to Cecil via cecil@straightdope.com.

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