You might have noticed that we recently got a wee bit of snow. You might also have noticed that the City has forgotten where the center of the universe is and plowed minor streets such as Mount Vernon and Route 1 better than and before the most important street in Alexandria. Clearly their priorities are mixed up. If the LesDunBelle area has been plowed better than we have, I’m going to be mighty irate because we were here first!
But I do not write to talk about the misalignment of city resources, I will save that for a snarkier posting in the future (feel free to chime in with your own…). No, today I write about shoveling snow. Yeah, most of us have been out there multiple times shoveling our walks, the sidewalks and our cars out (well, those who drive much. My car will stay safely ensconced in its white cocoon until next weekend at least!). And, some are not very nice neighbors as they have not shoveled but, for the most part, our block does a pretty good job. Not like the residents of 1415 Mount Vernon Avenue (SE corner of Mount Vernon and Nelson) who never shovel their sidewalk.
The sidewalks are passable, your cars could go somewhere but what about the roof? We’ve been hearing of some roofs collapsing and, there was the Knickerbocker storm back in 1922 so named because 98 people were killed when the roof of the Knickerbocker theater collapsed under the weight of the snow. So, the question is, should you shovel your roof?
Being dorkier than most, I set out on Saturday morning to figure this out. I won’t bore you with the details (email me if you really want to know them) but the short answer is that if your roof beams are in decent shape then you probably don’t need to worry. The load on the roof (assuming you live in one of our lovely rowhomes) is only about 10 pounds per square foot for a total of 2 ton. Now, 2 ton sounds like a lot but it is evenly distributed across the entire roof. And, it is melting so the load today (Monday) is less than yesterday. Additionally, wood, like steel, tends to “communicate” before it fails – you’d probably (but not always) hear creaking/cracking long before it failed.
Another way of looking at it is that we’ve got somewhere around 60 houses on the block so N ~= 60 and, being greater than 30 provides a valid population for statistical analysis. With a grand total of zero roofs on our block having failed during this snowfall so far, I’d say the odds of your roof failing are pretty slim.
Of course, I’m not a structural engineer; I’m not even an engineer! So if you’re really truly worried, don’t listen to the rantings of a dorky schmo on the intertubes, get the opinion of someone who is a real structural engineer.
UPDATE: Here’s a WaPo article published on 10Feb2010 which basically says the same thing as I – don’t bother shoveling your roof.