![]() They must be spaced no more than 4 feet (1219 mm) apart. They must be at least 1 inch by 4 inches (25 mm by 102 mm). If collar ties or ridge straps are installed to connect opposing rafters, they must be located in the upper third of the attic space. ![]() Ridge straps are permitted to replace collar ties. In a worst-case scenario, such as large snow loads, the roof and walls could collapse.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. If a gable roof is framed without either an engineered structural ridge, ceiling joists, rafter ties or another engineered solution, some amount of ridge sag and wall kick-out is nearly guaranteed. When it comes to the ceiling joist and rafter assembly, the International Codes have hit the bulls-eye. If you feel uncomfortable, call for the engineer. But often a code-compliant outcome calls for a professional engineer.Īs to whether the contractor uses method one, two or three, you have the last word. ![]() In other cases, he or she can set beams across the open span. Having said this, sometimes the contractor can place an engineered structural ridge beam directly below the ridge board. How is one of these wrongs undone? If the contractor asks, you should point out you are not in the design business, and it is his or her job to present you with a proposed solution. 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. Ceiling joists removed for headroom causes ridgeboard sag and wall kick-out.
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