Rock salt is sodium chloride cheap and poor.
Is magnesium chloride safe for roofs.
Calcium chloride is the most aggressive ice melter working down to well below zero and magnesium chloride is very good.
It melts ice faster than sodium chloride does works at lower temperatures than sodium chloride and also melts larger volumes of ice.
Most common high performance ice melters such as magnesium chloride or calcium chloride will certainly melt the ice but they may also cause staining of the shingles and could also cause corrosion of the gutters aluminum siding or fasteners.
It is not as likely to stain or cause corrosion as sodium chloride but it can damage wooden gutters.
It s environmentally friendly and safe around plants if it s not over applied and it works well sub zero temperatures.
Calcium chloride is the best salt to use on ice dams according to handyman glenn haege.
Although magnesium chloride still has risks associated it in my opinion it s the lesser of all evils.
In our experience magnesium chloride is the safest and all around best easy to find ice melt you can use in an absolute emergency.
If you re not careful however magnesium chloride.