3/24/2024 0 Comments Roof rafter collar ties![]() ![]() Similarly, rather than total roof height, the module asks for the roof pitch, which works out to "8.5 : 12". Rather than total roof width, the module asks for rafter plan length - or exactly half of the total roof width - which is 8.5 ft. The first step is to convert the geometry into inputs compatible with the module. Snow load = 35 psf on a horizontal plan area (equals 28.6 psf on a sloped area).Dead load = 20 psf on a horizontal plan area, including self-weight (equals 16.3 psf on a sloped area).Total roof width = 17 ft, with no eaves.Gravity Loading Only ExampleĪ roof is to be designed having the following geometry and loads: Both are simplified examples, but should be illustrative of the usage of this module. Two worked examples are provided here: one of gravity forces only, and one of a wind uplift scenario. Members may be selected from our database of standard sections, or a custom rectangular section may be defined with any species, grade, and dimensions.ĭesign can be a breeze by using our member selector or autosize features. The rafter member and each of the ties are set in the next sections. It is likely that none of this will need to be updated, as the default load magnitudes and rafter spacing are all pulled directly from the Project Defaults. The calculation is pre-filled with the roof loads, snow loads, and wind loads, an example of which is shown on the right. For the purpose of bearing calculations, the supports are assumed to be eclusively on the rafter, not any of the ties. Eaves & Rafter Supports: The length of the eave, equal to the distance between the edge of the rafter and the wall, as well as the bearing length of the wall, are set in one table.Note that, if there are two ties, it does not matter which tie is the "first" or "second", as long as it remains consistent throughout Depth of First/Second Tie : The depth of the collar and/or rafter tie from the roof ridge to the tie. ![]() If both are present, then select "Two", otherwise select "One".
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