Roof Rafter Thrust

A tension tie in the lower third of opposing gable rafters that is intended to resist the outward thrust of the rafter under load.

Roof rafter thrust.

Illustration of roof with rafter tie. Figure 2 is an illustration of a roof constructed using rafter ties. 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. Collar ties designed primarily to resist wind uplift must be located in the upper third of hr.

This horizontal load or thrust can be considerable especially on a low pitched roof. 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. 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. 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.