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0431 Methods of Reducing Rafter Spans - Roof Framing - Collar Ties
 
0431 Methods of Reducing Rafter Spans - Roof Framing - Collar Ties -

Image Text: Cross section > Collar ties > span > span > if the collar tie is more than about 8 feet long, it requires lateral support in the form of a 1x4 nailed perpendicular to the collar ties (prevents buckling) > roof rafter > ceiling joist > collar ties can be used to reduce the span of a roof rafter when the roof slope is 4 in 12 or greater > collar ties are not effective when roof slope is less than 4 in 12 > wall > Purlins > span > span > purlins - typically 2x6 minimum running perpendicular to roof rafters > must be greater than 45 inches > supporting struts should be 2x4 minimum, typically every 4 feet > bearing wall > struts longer than 8 feet should be braced to prevent buckling > Knee wall > span > span > dwarf wall or strut > ceiling joists must be 1 inch deeper than normal (or even deeper if the roof slope is 3 in 12 or less) to carry the extra load > install solid blocking between joists when ceiling below is finished

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STRUCTURE, Footings and Foundations, Description, Problems, Floors, Sills, Columns, Beams, Joists, Subflooring, Concrete Floor Slabs, Walls, Solid Masonry Walls, Wood Frame Walls, Masonry Veneer Walls, Arches and Lintels, Roof Framing, Rafters, Roof Joists and Ceiling Joists, Collar Ties, Knee Walls and Purlins, Trusses, Wood I Joists, Sheathing

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