Rafter length table1/4/2024 An 18-in-12 slope roof is one whose height above horizontal increases 18 inches up for every 12 inches of horizontal distance. Some texts may also call this the rafter line length so one needs to take care.ĭefinition of Roof Span: In a symmetrical roof such as the gable roof shown above, the total building width between the outer faces of the walls or wall top plates is the total area spanned by the roof or total horizontal span.ĭefinition of Rafter Rise or Roof Rise: a rafter's rise or the roof's rise is the total increase in vertical height over the rafter run or rafter span - the vertical distance shown in the center of our sketch above.ĭefinition of Roof slope: the slope of a roof or rafter is its angle off of dead flat or horizontal, expressed as the number of inches of rise or increase in height per foot or 12" of horizontal run or distance. Spanned by the rafter from the center of the ridge to the outer edge ofĭefinition of Rafter Span: the rafter SPAN is the same as the rafter's run: the total horizontal distance (parallel to the ground) below the rafter.ĭefinition of Rafter Line Length: Typical carpentry texts refer to the rafter's actual LENGTH from the rafter's plumb-cut face abutting the ridge board to the rafter's bird's mouth plumb cut as the rafter line length.ĭefinition of Rafter Total Length: When we add the additional rafter length necessary to include the roof overhang I call that the rafter total length. Let's look again at the drawing above and review some definitions of basic rafter and roof framing terms.ĭefinition of Rafter Run: You can see that for any rafter, the rafter's RUN is the horizontal distance Roof slope also as inches of rise per foot of horizontal run. Length in inches of the rafter type for the corresponding particular Inch number along the blade's upper edge. To the right of each of these rafter type line names are columns of numbers under each SIDE CUT OF HIP RAFTER OR VALLEY RAFTER.DIFF IN LENGTH OF JACKS 24 INCH CENTERS.DIFF IN LENGTH OF JACKS 16 INCH CENTERS.HIP OR VALLEY RAFTER LENGTH PER FOOT OF RUN.COMMON RAFTER LENGTH PER FOOT OF RUN - this is the top line in the rafter length tables.Holding the framing square with the front of the blade facing you and the tongue pointing down and on your right, you'll see six lines of rafter tables: Here is the Identification of each line of numbers on the blade This key is at the left end of the front of the framing square Tables give the length of the rafter per foot of horizontal run.Ībove we see the key to the lines in the rafter length table. You need first to understand the type of rafter you are cutting.įor a common rafter, or for each of the other rafter types, these To use the rafter length tables on the framing square blade front Normally roof slopes are expressed as inches of rise per foot of Our sketch above illustrates the concepts of run (horizontalĭistance) and rise (vertical distance) along the length of a rafter. The full scale number will be the length of the rafter in inches for The rafter tables allow you to calculate the length of a rafter byĬhoosing a "full scale" number that matches the unit rise (slope or Here we describe how to use the rafter tables found on the front How to Use the Framing Square Rafter Length Tables - the Rafter Tables We also provide an ARTICLE INDEX for this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need. This article series gives clear examples just about every possible way to figure out any or all roof dimensions and measurements expressing the roof area, width, length, slope, rise, run, and unit rise in inches per foot. Roof measurement methods: these articles explain various methods for measuring all roof data: roof slope or pitch, rise, run, area, and other features. How to use the rafter tables on a framing square to measure & lay out rafters or to figure roof pitch, slope, length, and all other roof and angle measaurements.Īlso use these tables for stair rise and run and riser heights and stair stringer layout. We have no relationship with advertisers, products, or services discussed at this website. InspectAPedia tolerates no conflicts of interest.
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