Roof Rafter Thrust

Rafter thrust occurs when the rafter tails the bottom of the roof members of a sloped roof where the roof meets the wall thrust outward and push the top of the wall outward.

Roof rafter thrust.

This can result in a bending outward at the top of the wall as well as a dropping of the roof ridge. Collar ties designed primarily to resist wind uplift must be located in the upper third of hr. Figure 2 is an illustration of a roof constructed using rafter ties. To resist thrust the irc calls for a structural ridge required for any roof with a pitch less than 3 12 or for each pair of rafters to be securely connected to each other by a continuous ceiling joist r802 3 2006 irc.

Connections can also pull apart. This thrust calculator gives rafter horizontal thrust at the plates l rafter span building width w load on rafter roof design load s rafter pitch t horizontal thrust wl 4 x run rise x on center spacing 12. To resist thrust the irc calls for a structural ridge required for any roof with a roof pitch less than 3 12 or for each pair of rafters to be securely connected to each other at the lower end of the rafter by a continuous joist. A tension tie in the lower third of opposing gable rafters that is intended to resist the outward thrust of the rafter under load.