Posted by: Chris Maloney | April 1, 2011

Roof Raking: When, Why, and How.

An automatic snow depth sensor

Image via Wikipedia

I’ve been trying to find an engineer’s explanation of roof raking, but no one has posted the torque and load dynamics. 

The problem is that, even if I had the exact snow dimensions and weight, I wouldn’t know what my roof’s maximum load is.  Evidently, even businesses that specialized in ice don’t know (see ice arena collapse.)

So let’s be clear.  You don’t want your snow load to hit maximum capacity.  You really don’t want it bowing under the load, because that can lead to ice formation under shingles and shorten the life of your roof. 

For those perfectionists out there, you really don’t want snow on your roof.  Here are detailed instructions about how to rake it all off.   

Ok, now that they’ve gone off to hire half of Maine to shovel off their roofs all winter, what about the rest of us? 

How good are you at predicting the weather?  Any snow that starts to melt, then refreezes, can generate an ice shelf that pushes back under the shingles from the edge and generates leakage.  I’ve got a brand new roof on my office, but the ice pushed under a little anyway and we got some leaks along the outside edge. 

So there is a good reason to use a roof rake to pull the snow away from the edge of the roof where the gutter is.  That’s also why most people just don’t have gutters in Maine.  I think I’ll be taking mine down.  It’s causing more problems than it solves. 

Beyond the gutter ice back up issue, you have to make some basic assumptions.  Anything less than a couple of feet of snow is likely to not crush your roof like a tin can.  If it did, there’d be few houses left.  Anything in the one to two foot range is an issue, because you don’t know when the next foot will be coming in.  The worst time is spring when you’ll get a heavy rain on top of a couple of feet of snow.  So if you see your elderly neighbors out thrashing around with a roof rake, do as they do.  Chances are they have a better sense of what’s dangerous than you do. 

If you’ve read this far, chances are you are a roof raking aficionado.  I reward such people with links to roof raking treasures like:  The Roof Razor.   Sort of a sports car for the roof raking set. 

Here’s a video for your viewing pleasure.

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