Midrafter Roof Deflection

Roof purlin single span.

Midrafter roof deflection.

But if the rafter deflects 2 at midspan and purlin deflects 1 5 at midspan. Deflection is the immediate sag produced when an object is set on a structural member. Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection. Based on our testing and research we concluded that certain rafters deflected out temporarily during extreme whether temperature change resulting in visible shingle deflection.

The osb roof sheathing had 8 8 5 of moister content the rafters 9 9 5. You have probably seen this and it is most likely due to roof deflection sag and creep. Then the total deflection is 3 5. Default deflection criteria for the following members.

This roof is composed of rafters which meet a center ridge beam. Ridge beam single span. The center beam is probably not terribly thick. See the table below.

What you see is the result of weight and time and gravity. If the sagging appears in the plane of the roof that is up and down between the ridge and the eave and from side to side the sagging is probably due to deflection and creep of the rafters themselves figures 8 and 9. Chapter 3 of the international residential code irc provides the maximum allowable deflection for a given structural member floor roof wall etc.