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.

Roof rafter thrust.

Connections can also pull apart. Collar ties designed primarily to resist wind uplift must be located in the upper third of hr. 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. 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.

Tim healey in a roof with a non structural ridge rafter ties which resist the outward thrust of the rafters can be raised a maximum distance hc that is no more than one third the distance between the top of the supporting wall plates and the top of the ridge hr. Illustration of roof with rafter tie. 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.