The life expectancy of a wood shingle or shake is 25 to 30 years. Some can even last up to 50 years. They are more expensive that asphalt shingles, but they’re popular because of their charming rustic appearance. It is recommended not to install untreated wood shingles and shakes where heat and humidity are severe because they are quite susceptible to decay from moss, mildew and fungus. Treated shingles should also be installed on low-slope roofs as a low-slope will not shed water as well as roofs with a higher pitch. Treated shingles should also be used on roofs shadowed by overhanging trees as this condition would keep a roof wet longer.