Ceiling joists should be continuous or properly joined above interior walls according to the codes. They should also connect to rafters at the top plate when run parallel to the rafters and fastened to the top plate if not parallel.
A rafter span is measured from the center of the ridge or ridge beam to the outside face of the supporting top plate, or the outer edge of the birdsmouth or cleat. How far a rafter can span is determined by the wood species and grade, spacing between rafters, and the loads it must support.
The load includes factors such as whether the ceiling is finished or not, weight of roofing asphalt vs metal vs slate vs tile , wind loads, and snow or live loads. The span decreases as the spacing and load increase and is dependent on the type and grade of timber. The stronger the species and higher the grade, the farther it can span.
Roofs with lightweight roofing and no ceiling commonly have a dead load rating of 10psf and those with heavy roofing are rated at 20psf.
However, rafters with light-weight roofing and a drywall ceiling have a dead load of 15psf while a plaster ceiling is 20psf. Heavy roofing changes the dead load rating to 25psf and 30psf respectively. Decking is the material that spans and fastens to the joists upon which you walk and place furniture.
Interior decking today is usually plywood or OSB. Loads affect joist spacing and span which also impact decking choice. Hot tubs require additional support, so always reference your local building code when building a deck. Pressure-treated lumber is often made from the most available local rated material, which in my area is SPF spruce-pine-fir.
Joist spans for exterior decking differ from interior spans of equivalent species and grades too. Most decks are rated for a 10psf dead load and a 40psf live load, or a total load of 50psf.
Exterior decks are commonly rated for a live load LL of 40psf and a 10psf dead load DL , for a 50psf total load. The wood species, grade, and spacing between joists determine the distance a joist can span. The building code span tables for deck joists include the cantilever distance. The cantilever is how far a plank can extend beyond the beam without support.
It should be noted that deck joists span shorter distances than interior joists with equivalent factors. So, make sure to reference the correct span tables. Wood has different strength qualities depending on what species it is. Southern pine, perhaps the most common wood used for dimensional lumber, is stronger than other softwoods, such as cedar, redwood, douglas fir, and red pine. Cedar and redwood, in comparison, can only span up to 5 feet 2 inches on a deck with 6-foot joist spans.
Since dimensional lumber used for structural framing is so critical to the safety of the structure, lumber has different levels of quality. Lumber rated No. Select Structural is the highest grade of lumber, offering superior strength. How does this affect the span? Returning to our deck framing example, No. In comparison, No. Select Structural lumber, meanwhile, can span up to 11 feet 4 inches. While the differences may seem nominal, keep in mind that the amount of distance a beam can span can determine the number of beams and support posts you need to install, impacting the amount of time and money it takes to complete a project.
Depending on use, some 2x6s must support more loads than others. A joist on a deck or floor may support more weight than a roof rafter because it must handle a greater load. A rafter, however, in northern climates may need to be stronger to support heavy snow loads. Decking, meanwhile, has a short span because it is placed horizontally versus vertically.
How does load affect span? The load is delineated by two types: dead load and live load. Dead loads are static forces that remain constant. In the case of a deck beam, it refers to the weight of the joists and decking above it.
Live load refers to occupancy. In the case of a deck, this would be the weight of people and pets on top of the deck. For a deck with a maximum live load of 40 pounds per square foot and a dead load of 10 pounds per square foot for a total load of 50 pounds per square foot , the maximum span is 9 feet 5 inches for a No.
That span decreases as load increases. In this way, can I use 2x6 for floor joists? In general terms, joists spaced 16 inches on center can span 1. A 2x8 up to 12 feet; 2x10 to 15 feet and 2x12 to 18 feet. The larger the deck, the larger the joists. Furthermore, how much weight can 2x6 floor joists hold? To give you a general idea though, floor joists are sized to support 40 pounds per square foot of "live" load moving weight or 10 psf "dead" stationary load. As incremental parts of a building's structure, joists are not easily replaced.
You can, however, strengthen the joists by securing another length of wood to the existing joist , called "sistering," or reduce wobbly floors with block inserts between the joists , called "blocking.
If the floor is bouncy but the joists are not sagging, the simplest fix is to reinforce the joists by installing additional joists adjacent to the original ones. New two-by-six joists are cut to fit snugly beside the old ones. How far can 2x6 floor joist span? How far can you run a 2x6 floor joist?
You can span about 9' with your 2x6, if you care. Are two 2x6 stronger than a 2x8? In bending, a joist composed of two 2x6's true dimension 1. How far can a 2x6 Rafter span without support? The table states that 2 X 6 rafters spaced 16 inches on center o.
Another option are 2 X 8 rafters spaced 24 inches o.
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