Gambrel Roof Collar Ties

The prescriptive provisions of the building code require rafter ties on each rafter pair and collar ties every 4.

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. In this case the collars. Collar ties as per current irc code are required to be at least 1x4 nominal material but are most commonly 2x4 s. This is on a conventional stick frame non truss structure as engineered roof trusses do not require collar ties from a framing material as they are tied together with metal.

Like rafter ties collar ties are horizontal members that tie the rafters together and resist the force that tries to make the bottoms of the rafters spread horizontally and push the walls outward. I ve never framed a roof before but when i asked for details i didn t see collar ties in his drawing. The guidelines i am about to explain for you outline the steps i use when i am designing my gambrel shed plans barn shed plans and small barn plans. A gambrel style shed roof offers the most storage space in the attic when compared to a gable or saltbox style shed roof.

The owner plans on using an engineered ridge beam and tells me that such a beam will eliminate the need for collar ties. Attach other 2 angle brackets to rafters and secure with. Use a roof jack on the sagging roof rafters to raise them back into position. The upper collar tie does not experience the tension that the lower rafter tie is resisting if that tension is resisted in the upper third the roof is probably on the ground.

If your roof is already sagging by the pressure of the roof you can use the collar ties to help the roof rafters bend back into shape. Compared with the traditional gambrel frame this method removes almost all of the complex analysis. Collar ties prevent rafter separation and uplift. The 2015 international residential code does not require collar ties or collar beams.

I can now analyze the whole roof system as a simple three hinged arch. The rafter ties are incorrectly labelled as collar ties. 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. Step 5 repairing sagging roofs with collar ties.

There are some exceptions however when collar ties might be useful even in a conventional attic roof. 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.