Gambrel Roof Collar Ties

The 2015 international residential code does not require collar ties or collar beams.

Gambrel roof collar ties.

A friend has decided to put a gambrel roof on a 20 40 barn and has asked me to help in the framing. The owner plans on using an engineered ridge beam and tells me that such a beam will eliminate the need for collar ties. However in those situations when they are specified collar ties or ridge straps are usually installed in the upper third of the roof between opposing rafters. Collar ties collar ties are an alternative to rafter ties in framing where a conventional ceiling is not desirable.

I can now analyze the whole roof system as a simple three hinged arch. There are some exceptions however when collar ties might be useful even in a conventional attic roof. In high wind areas uplift can tear a roof off of a house if it s not properly attached. The collar ties are used to strengthen the roof rafters to prevent them from buckling or sagging under the weight of the roof.

Like rafter ties collar ties are horizontal members that tie the rafters. 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. A gambrel style shed roof offers the most storage space in the attic when compared to a gable or saltbox style shed roof. 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.

Collar tie is a colloquial term for collar beam. I ve never framed a roof before but when i asked for details i didn t see collar ties in his drawing. 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. For example very long rafters in a relatively steeply pitched roof slopes above 6 12 for instance may benefit from a stabilizing effect if adequately connected collar ties are installed on every rafter pair.

Using the gussets eliminates the need for the collar tie.