![]() For example, when a ridge board does not have sufficient depth to provide full bearing, the rafters can be overstressed in compression and cause crushing of the wood. Even though a ridge board is not considered a structural member, the geometry and dimensional requirements listed in the IRC for ridge boards are no less important. To further illustrate that the ridge board is not functioning as a structural beam, it is interesting to point out that IRC allows the ridge board to be eliminated with use of gusset plates between the rafters. The IRC requirements above are focused on minimum geometry and bearing dimensions for the ridge board to function as a nailing board between the opposing rafters. Ridge boards shall be not less than 1-inch nominal THICKNESS and not less in DEPTH than the cut end of the rafter… Rafters shall be framed not more than 1½-inches offset from each other to a RIDGE BOARD or directly opposite from each other with a gusset plate as a tie. The IRC requirements for a ridge board are relatively brief and listed as follows: Now that we have established the basic function of a ridge board, let’s move on to the specific requirements of the building code. ![]() Figure 1: Diagram of conventional system with ridge board. Figure 1 provides an illustration of a conventional system with ridge board. Simply put, a ridge board is a non-structural nailing board located at the peak between the tops of the rafters. Its technical function can be best summarized by the following definition adopted from Wood Frame Construction Manual (“WFCM”) produced by the American Wood Council (“AWC”):Ī NON-STRUCTURAL member used at the ridge of a roof to provide a common nailing surface and point of bearing for opposing roof rafters. The ridge board is located along the peak of the roof in a conventional system. In its most common form, the roof is constructed with rafters along each slope with ceiling joists along the bottom which encloses an attic space (referred to as “conventional system” throughout this discussion). The most common type of residential roof is a simple gable or hip configuration which generally consist of a peak (ridge) and sloped sides which resembles a triangular shape when viewed from the side. Similar language and principles exist across other IRC editions and industry standards as well. Code references throughout our discussion will come from the 2015 edition of the IRC which is the most common edition currently adopted across the United States. Part 1 will focus on the difference between non-structural ridge boards and structural ridge beams. This three-part blog aims to provide an overview of these topics with the hope of providing a concise overview of residential roof framing basics as well as common deficiencies along the way. ![]() In our experience, the most common residential roof framing issues center around a misunderstanding of the following 3 topics and components: Whether consulting for a litigated matter, reviewing details for loss control, conducting cost estimates, or performing structural repair design, we have seen issues related to residential roof framing from a wide range of perspectives. VERTEX has a unique perspective in dealing with the construction and design-related issues because of our diversity in clients, the scope of services, and the diversity of experts. As the desire for more complex roof shapes and open ceiling configurations increases in newer construction, the risk of claims from roof framing issues will likely also increase. There is often confusion with the requirements even among licensed structural engineers who aren’t familiar with residential construction. However, in our experience, the prescriptive requirements of the IRC can often be misinterpreted or misunderstood by contractors, architects, and even building officials leading to deficient roof framing. Instead, the International Residential Code (“IRC”) allows for the general contractor or the architect to follow the prescriptive requirements of the IRC to ensure adequate structural framing. Errors and deficiencies in the construction and design of residential roof framing can lead to costly insurance claims or litigation and can also make the residence more susceptible to property damage from storm events such as snow and wind loading.įor areas throughout the United States that are not located in high wind or seismic zones, construction projects for one- and two-family dwellings do not typically require design from a licensed engineer. In the course of investigating hundreds if not thousands of forensic projects per year, it’s hard to find a more commonly misunderstood or incorrectly constructed item than residential roof framing.
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