Purpose Of Roof Collar Ties

A collar tie is a horizontal roof rafter compression connector that is located in the uppermost third of the span of a pair of opposed sloped or gable roof rafters.

Purpose of roof collar ties.

Contrary to popular belief collar ties are not there to support rafters or to keep walls below from spreading under the weight of the roof. Collar tie 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. By upper third here we mean one third of the length of the rafter from ridge to top plate. This collar tie roof is suitable for the span varying from the 4 to 5 5 this roof is used for a maximum span of 4 8 m.

The design of collar tie roof provides greater ceiling height if it is required. Rafter ties prevent spreading. 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. Collar tie is a colloquial term for collar beam.

The purpose of the collar tie roof is to extend first floor rooms into the roof space and so limit the largely unused roof space. The most common reason for installing collar ties is to prevent rafters from spreading apart under load. However in a conventionally framed peaked roof like the kind you describe collar ties would probably serve little or no function since the attic floor joists serve as ties to prevent the rafters from spreading. Collar ties collar ties are connections between opposing rafters at the upper one third of the roof frame area just below the ridge and they are required at a 48 4 maximum spacing which is every other rafter of a 24 on center spacing and every third rafter with 16 on center spacing.

Collar ties collar ties must be provided in all coupled roof construction. The 2015 international residential code does not require collar ties or collar beams. Where the rafter span is such that it requires support from underpurlins collar ties are fitted to opposing common rafters at a point immediately above the underpurlins. This is especially important if the home is in the northern climates where snow accumulates on roofs or if there are multiple layers of roofing materials.

Collar ties prevent uplift. They supplement the ceiling joists and prevent the rafter couples spreading.