Instructables

Is Calcium Chloride safe to use on roof or gutter ice dams?

In cold climes, snow buildup on roofs often leads to ice dams, usually at the gutter. When the snow melts, the dam can route water under roof shingles and cause roof damage.

Is Calcium Chloride safe to use on roofs? (Sodium Chloride is not, due to it's corrosiveness.)

roofice4 years ago
The key to using ice melt to prevent ice dam roof leaks and plugged gutters in winter is two fold.  First, put non-staining ezdeicer ice melt in a freeze tested ice melt sock material that will allow the ice melt to create a solution that will keep a small channel melted in the ice dam to drain water.  Second, is to lay the sock vertically up the roff so it crosses the ice dam.  Very little ice melt will be used in this manner (actually 4 lbs/sock can last til the first real thaw) and no damage to roof or gutters will occur in comparison to thousands of dollars of water damage to property without ice melt socks.

If you lay the sock horizontally you will never open any channels.  The only thing you will do is have to fill the sock constantly and thus kill the grass around your gutter drains. 
driveajeep3 years ago
Yes, I believe flydrifter hit the galvenized roofing nail right on the head. CHLORIDE = CORROSIVE. We've tried the acetate based roof products from the web site, and they worked great, with no sign of corrosion or damage to anything. Roof or landscape. The research we did paid off and we feel good about being friendly to the environment.
flydrifter3 years ago
Calcium Chloride (CaCl) is corrosive to certain metals and really should not be used on rooftops for a couple of reasons: Roofing nails are basically zinc coated iron (galvanized). Calcium chloride will eventually corrode these. Another concern is that after melting, you will have runoff of water onto sidewalks or patios which will re-freeze (because it's diluted) and be very slippery. CaCl can also be harmful to certain plants, such as evergreen trees.
Most people don't know, but there are a couple of very safe products available for use on rooftops that are less corrosive than water and harmless to plants. One is pure CMA (Calcium Magnesium Acetate), and the other is NAAC (Sodium Acetate). Greenicemelt.com carries pure CMA and pure NAAC. Here are some websites that show corrosiveness of Calcium Chloride:

http://www.engineeringtoolbox.com/metal-corrosion-resistance-d_491.html

http://www.buzzle.com/articles/safety-measures-for-calcium-chloride.html

And, consider why does CaCl need to be "corrosion inhibited"?
http://www.calciumchloride.com/ice.shtml
goodrite5 years ago
First of all blackboard chalk is not calcium chloride, but a soft mineral,Calcite, which is chemically calcium carbonate. If blackboard chalk were calcium chloride, it would quickly turn into a puddle of liquid in your hand since calcium chloride readily picks up water from the air. The MSDS for calcium chloride mentions that it can corrode aluminum. This makes chemical sense. However you also have to remember that the calcium chloride will be used in the gutter in the winter when the temperatures are quite cold. This will slow down the corrosion reaction considerably. I have new gutters on my house and I noticed that they are coated inside which will probably make the corrosion issue of little concern. I plan to use the Calcium Chloride in my gutters this winter to minimize ice dam formation, and will report back to this medium as to how it went.
salec5 years ago
AFAIK Calcium Chloride is AKA common (blackboard, school) chalk. How corrosive is chalk?
tgwinn5 years ago
Well, the corrosive part of Sodium Chloride is the Chloride ions, so any ionic chloride compound is going to have the same probloems. Supposedly magnesium chloride is less corrosive than sodium or calcium chloride, but in all cases you're going to see some metal corrosion.