Its function and location is summarized in the following definition from Wood Frame Construction Manual (“WFCM”) produced by the American Wood Council (“AWC”):

A rafter tie is a horizontal framing member that extends across the roof span to resist the outward thrust at the bottom of the rafters and effectively “tie” the rafters into their proper triangular shape. the triangular shape flattens down and out. When vertically loaded, the ridge tends to deflect downward, and the bottom of the rafters tends to push outward, i.e. The most common type of residential roof is a simple gable or hip configuration, consisting of a peak (ridge) and sloped sides, resembling a triangular shape when viewed from the side. Similar requirements and principles exist across other IRC editions and industry standards as well. Code references throughout our discussion come from the 2015 edition of the International Residential Code (“IRC”), the most common edition currently adopted across the United States. In Part 2, we will discuss the difference between rafter ties and collar ties (and no – they are not the same thing!). Part 1 on ridge boards and ridge beams can be read here. This three-part series aims to provide an overview of these critical components in an effort of providing an overview of residential roof framing basics, code requirements, and common deficiencies. In our experience performing hundreds of forensic evaluations related to residential roof framing per year, the problems often stem from misunderstanding of the following three critical components of residential roofs: PS - Blocklayer - Ive noticed you on the website.Errors in the design and construction of residential roof framing are common causes of property damage, liability claims and litigation. *I was intending to use 140x45 on the hips and ridgeboard to ensure the strength overall is good This turned out longer than I thought.so in summary the key questions are:ġ) Will 90x45 rafters 2400 long be ok on a hip roof supporting 18kg/m2?Ģ) Will adding collar ties to 2-3 out of the 7 rafters provide sufficient strength/support? Does adding a collar tie increase the total span of the rafter? I was also intending to put collar ties approximately 500mm down from the ridgeboard on the first and last rafter.

In addition, I was intending to run the rafters at 600mm centres meaning ill need 7 common rafters. I wanted to ask if you feel that 90x45s would prove to be strong enough and not warp or bend over time? the shingle roof, with 12mm ply should weigh less than 18kg/sqm so its not like the roof is holding concrete tiles. I was intending to cut birdsmouths to sit the rafters on the beam.Īll the literature seems to suggest I have to use 140c45 rafters, but i do prefer 90x45 for the overall athsetics and cant find any span data about 90x45's. Im planning for the rafters to be about 2400mm long, taking into acount a 400mm overhang on a 25-30deg pitch roof. Im a little stuck at the moment regarding the rafters. I suppose I call it a gazebo, but to clarify, it will be rectangular, not octagonal etc.īasically,Im planning to build a 6m x 3.5m gazebo, primarily utilising treated pine, with the roof constructed with 12mm ply and asphalt shingles fitted, both for appearance and weight. It was really helpful for me when buiding a deck recently! I really would appreciate some advice and tips about hip roofs as im about to build my own Bali Gazebo.

Rafter ties on hip roof