Hip Roof Framing Collar Ties

In this how it works article managing editor debra judge silber explains the role of collar and rafter ties in the framing of a roof.

Hip roof framing collar ties.

The international codes i codes are the widely accepted comprehensive set of model codes used in the us and abroad to help ensure the engineering of safe sustainable affordable and resilient structures. Collar ties are necessary to prevent separation of the roof at the ridge due to wind uplift. Collar ties are nailed to common rafters with four 8d nails to each end of a 1 inch tie. I expect you have a beam spanning the distance between the 3 foot sections to carry the jacks.

Collar ties are required in the upper third of the roof system to provide restraint against the roof being pulled upward and outward from wind. Collar ties are used in the upper third of the roof frame about ever four feet to resist upward hinging in a violent wind that can take the ridge apart other wise. If 2 inch material is used for the tie they are nailed with three 16d nails at each end. The hhrc is a heavy field slopeable connector that attaches hip and roof beams to the end of a ridge beam.

The prescriptive rafter span tables on pages 4 and 5 are modeled on the tables in the irc and are subject to the restrictions for rafters as defined in both the irc and ibc. If there was no ridge beam the four hip beams would meet at a point and would form a stable structure if hinged at all five nodes. The international code council icc is a non profit organization dedicated to developing model codes and standards used in the design build and compliance process. Collar ties may take up space in the attic of your home but they are there for a reason.

A hipped roof can be designed without rafter ties or internal columns by using the wall plates as tension members and the roof deck for stability. By upper third here we mean one third of the length of the rafter from ridge to top plate. It accommodates heavier hip loads and can be used with structural composite lumber glulam and solid sawn lumber. Rafter ties are used in the lower third of the rafter and resist outward thrust of gravity on the walls.

Code required in some southern tornado prone states. A collar tie is a tension tie in the upper third of opposing gable rafters that is intended to resist rafter separation from the ridge beam during periods of unbalanced loads such as that caused by wind uplift or unbalanced roof loads from snow. Definition of collar tie in roof framing. Without roof deck the four hip members together with a four foot long ridge beam form an unstable structure when hinged at all six nodes.