The Importance of Roof Pitch
Q: Everything being equal (ventilation, shingle type, climate, etc.), which roof will last longer: one with a steep pitch or one with a shallow pitch? Seems to me a steep hillside erodes more quickly than a low slope, so I'd think that roof shingles would wear out more quickly on a steeply sloped roof.
—George, Oglesby, Ill.
A: Tom Silva replies: It's difficult to say. On one hand, a steep roof is less likely to collect leaves and other debris that hold moisture against the shingles and invite the growth of moss and algae. On the other hand, that same roof in an unshaded area facing due south will take the full brunt of the sun, which is hard on any roof.
Actually, factors other than pitch have a greater effect on shingle durability. The side facing your worst weather typically fares worse than the leeward side. Likewise, a roof system that isn't vented properly and allows heat to build up beneath the roofing has a shorter life than one that is vented.