![]() You can then plug the numbers into the Pythagorean theorem formula to solve for the hypotenuse, i.e., the length of the rafter. (Slope length cannot be ignored for wind load analysis, though. To determine roof rise, make a proportion between the roof slope and the rafter run (roof span + thickness of the ridge board 2) and solve for the missing variable. I ignore the slope factor altogether for snow load reduction which adds another measure of conservatism. Roof Rafter Calculator estimates the Length, Board Size, Quantity, Cost per board and Total Cost of Lumber The estimates are based on your house foot print. To do this, I use conservative (too heavy) dead loads and full snow loads regardless of pitch. MAIN ROOF Run of common rafter 15 ' 0 ' x 1.202 ( see roof table ) 18 ' equals length of common rafter. The diagram located at the right is applied to provide roof dimension precisely as well as work out board length more perfectly. It can be used for making calculation of rafter length, board size, quantity, cost per board and total cost of lumber. However, in my practice, I typically use the horizontal run of the roof for both types of load. c EXAMPLE IN USE OF ROOF TABLE, . With this online calculator, it is possible to workout rafters for your roof. Technically you should use the actual rafter length when adding up the weight of roofing materials. BOCA also allows you to reduce the snow load for roofs with slopes greater than 30 degrees, presumably because snow will slide or blow off steeply pitched roofs.įor dead loads, you are correct. The BOCA code recognizes this and allows you to use the horizontal projection of the roof when calculating snow loads. ![]() This is because as snow falls vertically it spreads itself further along a sloping rafter and so accumulates less depth. Actually, with snow, you don’t get more load along the slope of the rafter you get the same load as a flat roof with the same run would get. All we do now is use a calculator to multiply 1.610 by the measurement in the book: 1.1543 x 1.610 1.858m. This means that for every 1m the rafter travels horizontally, the angled length of the roof will be 1.1543m. ![]() But isn’t it more accurate to figure the weight of snow and roofing materials by measuring along the actual length of the rafter? Thus, as the roof gets steeper, the rafter gets longer, and the weight of roofing materials increases.Ī. The length of rafter per meter of run is 1.1543. Common Plumb to Plumb Line Length (inches). Center to Center Rafter Spacing (inches) Rafter Thickness. I often see roof loads calculated based on the horizontal run of the roof. Horizontal Span of Rafter (inches,run) Roof Pitch (inches rise, e.g.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |