3/19/2024 0 Comments Roof rafter span table 802.5.1![]() As of this date, however, using verbal instructions and a note on the permit card, I’ve seen a 100-percent correction rate. Ultimately, the remedy may require a stop work order. ![]() Specifically, the aforementioned Section R 802.3.1 also states: “Where ceiling joists or rafter ties are not provided, the ridge formed by these rafters shall be supported by a wall or girder designed in accordance with accepted engineering practice.” For the past several code cycles, both code commentaries have also contained a detailed description of this vital link, including some useful diagrams. And, both the International Building Code and the International Residential Code prohibit this. Why is the code so precise about this rule? Because without rafter ties, the ridge sags, and the top of the walls supporting the lower ends of the rafters push or “kick” outward. When using this method, the rafter spans must be adjusted downward, according to the formula at the bottom of Tables 802.5.1(1) to 802.5.1(8). As an option, a framer may install the rafter ties above the top plates within clearly defined limits: The ties must not exceed the bottom third of the vertical height of the ridge above the plates. In this alignment, we call them ceiling joists. These ties are mounted on the top plate, fastened against and parallel to the rafters, and continuously connected from outside wall to outside wall. Rafter ties, on the other hand, do reinforce the outside walls. ![]() The collar ties hold the exterior building walls together about as much as a wad of strawberry chewing gum. This stabilizes the connection between the ridge board and the tops of the rafters. Whenever I point out this framing flaw during an inspection, the contractor says, “But I have collar ties there.” I now believe this matter should be engraved in solid gold as a building inspector’s decree: One shall not use collar ties to hold exterior walls together.Ī framer must attach the collar ties to one side of the roof rafters, horizontally, and in the top third of the vertical distance between the ridge board and the plane of the top plates (International Residential Code, Section R 802.3.1). ![]() Framers, like Seabees, are “can do” people. I believe this happens because contrary to the approved plans, some enlightened soul decides it would be more stylish to have an open ceiling. But, despite the training now mandated by several states, along with explicit code language, this gaffe in one- and two-family framing seems to occur as much today as it did 20 years ago. Why do some bright residential builders confuse collar ties and rafter ties? And, how is it the same folks piggy-back on this blunder by framing a cathedral ceiling into a gable roof without using a structural ridge? The answers baffle me. A Code Enforcement Officials comments when asked about rafter framing. ![]()
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