A.Christopher DeBlois, a structural engineer with Palmer Engineering in Tucker, Ga., responds: Most roof collapses from heavy snow loads are caused by connection failures, not failure of framing members. In fact, actual breakage of rafters is fairly uncommon except for with flat roofs.

To help visualize loading-connection issues, picture two extension ladders leaning against each other. If two people of about the same weight want to climb them, one on each side, the system is stable so long as the bottom of each ladder is braced and can't kick out. This is a balanced loading situation, and illustrates the importance of a good...

or Register to read the full article.