Attaching snowguards to comp shingl roof
Our house has a couple of steep roof valleys in which ice builds up over the winter. Come spring, large chunks (200lbs or more) break off and slide off the roof. The roof is asphalt shingles, but the valleys are steel.
Obviously this is a safety hazard, and will become more so as I plan on putting a deck in the area where the pieces of ice land.
I think the best approach is to to put a snow guard at the bottom of these valleys similar to what is used at the bottom of metal roofs. I picture L shapped brakets, screwed to the rafters, with a bar run between the brackets a couple inches above the roof.
Now for the question. How do I screw the braket to the roof. I can slide the bracket under a shingle and screw in under the shingle, simliar to a roof bracket, but my concern is that given the weight of the ice, nails or screws will pull out. I could lag it to the rafter, but the I’m concerned that a lag head under a shingle will create a point of water inflitration (as well as a very obvious hump in the shingle).
There is 1/2″ osb under the valley, and I don’t have access to the under side to add blocking.
Any thoughts on how to attach the snow guard, or alternative approaches? Thanks.
Replies
Any penetration in the roof where you have ice building up is likely to leak. Water has to dam up before it becomes ice. Ice build up like you describe is often caused by poor insulation combined with inadequate roof ventilation. I would start there.
I would also consider heat tape that you turn on when the ice first starts to build up. I would be reluctant to suggest any solution for a two hundred pound block of ice. When it warms enough from below and starts to melt at the bottom it moves like you greased your roof under that ice.