Rafters And Roof Ridges Are Normally Under Tension

That s true for horizontal ties in the lower third of the roof.

Rafters and roof ridges are normally under tension.

In many situations you ll find that ceiling joists installed parallel to the rafters are intended to function as rafter ties. It s an indication that you should look carefully for other problems in the roof framing. Flat roofs normally have venting systems. If you see sagging rafters recommend stabilization by a qualified contractor.

Roof vents are required for roofs with unconditioned attic spaces. A tension tie in the upper third of opposing gable rafters that is intended to resist rafter separation from the ridge because of wind or unbalanced roof loads. Roof sag or roof collapse forces. A horizontal timber uniting two opposing rafters at a point below the ridge usually in the upper half of the rafter length.

Mathematicians and engineers discussing collar ties and rafter ties explain that collar ties and rafter ties or ceiling joists under a gable roof are in enormous tension and that the mathematics of the roof forces are the same for collar ties and rafter ties. A guarantee by a surety company that a roofing manufacturer will repair a roof membrane or covering under the conditions listed in the bonding contract. A rafter tie is a tension tie in the lower third of opposing gable rafters that is intended to resist the outward thrust of the rafter under a load. A ridge board was not always required and the photo above of the attic in a 1920s era house shows a roof framed without one.

A pair of rafters is called a couple in home construction rafters are normally made of wood exposed rafters are a feature of some traditional roof styles. Also called collar tie. That said i recommend having a local structural engineer come out and review the situation if you are not such an engineer yourself. The roof framing mock up below shows a standard rafter tie.

Under the roofing paper felt along the rake edge. As such i don t see significant risk here. We include photographs of collapsing wood framed roofs and photo sequences. A ridge beam carries the loads of the rafters connected to it and must be both strong enough to carry the weight and well supported at the bearing points at each end to transfer the loads down to the ground.

This article describes explains the directions of forces in roof structures illustrating downwards force horizontal thrust and the causes of rafter sags rafters that disconnect from the ridge or top plate and why a sagging roof pushes the building walls outwards at the wall top. Rafter tie a tension tie in the lower third of opposing gable rafters that is intended to resist the outward thrust of the rafter under. An attic with an area of 600 square feet with ridge and soffit vents should have a total vent area of square feet. If you see rafters installed on centers greater than 24 inches look for signs of failure such as sagging of the rafters.

A ridge board with the ceiling framing below acting as a tension tie is nearly non structural and of nowhere near the importance of a a true ridge beam.