Saturday, 26 January 2013

Take a load off

This has been an intensely snowy winter so far.  We haven’t really had any warm weather to speak of to keep the snow down to a manageable level.  I have been pondering the importance of removing some of the snow from my house in recent days, as I am sure the building is groaning under such a heavy load.  What are the pros and cons of doing this, and is it something I should consider hiring out?  Thanks so much, love reading your column,



Well thank you so much, Gilles,

And a happy new year to you and all you who read this every week.

Well you’re not the only one who’s been mulling this one over in recent days.  Many of my neighbours have braved the cold and gravity to relieve the stresses of their overburdened roofs.  If I’m being honest not everyone needs to worry about the accumulation of snow, but then some people need to worry a bit more than they probably do already.  We have to understand that homes in our area are engineered to withstand the hundred year storm; essentially the worst Mother Nature can throw at us once every hundred years.  So be that three feet of snow or 100mph winds or a foot of rain, our homes are built to withstand it.  Now that being said there are going to be a number of factors that will affect the worthiness of our structure to tough out the worst storms: age and condition of the house and its structural members, integrity of said structural members, any alteration, renovation, or repair that has been done to the structure or the building envelope as a whole.  These changes can include but are not limited to replacement of roofing material, additions, changes in size of doors or windows, addition of roof area (ie. porches, carports, lean-tos, etc.).  In the case of snow loading, any of these things can have a dramatic effect on when, where and how much snow accumulates in a given area on the roof.  If a simple roof is left unaltered and is in a good state of repair, it will collect snow evenly and the weight will be distributed evenly down through the load bearing walls that have not been in any way altered or compromised.  If we now build a large addition on this house attached perpendicular to the original structure, put in a patio door where there was just a small window, replace the roofing material and neglect to put an ice and water membrane on first, and maybe add a 16 foot car port for good measure we have the potential for some really significant issues with a snow like we’ve gotten recently.  First you now have two large valleys where the addition meets the house which weren’t there before.  This will affect the way the wind blows over the house and how the snow is distributed over it.  Snow will drift here and concentrate the weight in one location, directly above that nice new patio door you installed off the kitchen that was just a window before.  So did you frame that header correctly when you installed it…are you sure?  If you didn’t, your roof is now bearing down with about five tons of additional weight and something’s got to give if that weight is not being transferred properly.  Now when the melting starts you’re going to want to be really sure that you installed that ice and water membrane under the first six feet of shingle. Because that nice drift hanging off your eaves trough is also blocking your eaves trough so the gallons of melt water have nowhere to go.  So what happens to it?  Well, it runs down to the gutter and since it can’t drain away it freezes.  As more melt water runs downhill it hits the newly minted ‘ice dam’ and gets stopped.  With nowhere else to go it freezes too. And so on and so on, ad nauseum.   Since your shingles were only designed to protect your home from water as gravity would have it, when the water starts backing up hill due to this damming effect the shingles are useless to protect it.  This is where the added layer of protection from the ice and water membrane is invaluable. 

So I digress a bit here but I think it helpful to understand the forces that are working on your house.

To answer your question directly, should you, depends.  Should you hire it out, yeah, probably.  There’s a lot of risk involved and you really don’t want to fall even if it would be a soft landing.  What are the risks, well first of all, falling.  Damaging the shingles with shovels is also a concern.

My best advice is to stay in tune with your house.  When things are happening, stay on top of it.  If there’s a lot of snow, observe how it is collecting. As melting or raining is occurring, watch for signs of damming, leaking, etc.  Icicles are a telltale sign that your roof is not adequately draining.  Monitor these because if they get large enough they can rip the gutters right off the house.  Seen it! Consider one liter of water or ice weights a kilogram.  A forty foot gutter will hold about 150 kilograms of ice plus however many icicles grow along its course.  It’s not unusual to have the equivalent of two full grown men hanging off the eaves trough, not a load it was designed to carry.

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