The maximum span of a 2x8 floor joist depends on several factors, including the wood species, grade, spacing between joists, and the expected load. In general, for residential construction using standard framing lumber such as Douglas Fir-Larch, a joist can span approximately 10 to 13 feet when spaced 16 inches apart.
The span of a 2×8 floor joist depends on the material and spacing, but in general: For Douglas Fir, a 2×8 joist can span up to 12 feet when spaced 16 inches O.C. and carrying a typical residential live load of 40 psf (pounds per square foot) and a dead load of 10 psf.
By ``rule of thumb'' you can use 2x8 to span up to 12 feet. I would not recommend doing so, though, as your main floor could get a little bouncy. (The rule of thumb for 2x6 would be a maximum span of 9 feet.) So replacing your 2x10 joists with 2x8 would ultimately only gain about 2'' of head room. This chart:
It depends on your beam span. For a beam span of 11 ft, the joists can only span 6 ft. If the beam span is decreased to 8 ft, the joists can span 12 ft. And 2x8 joists can span a max of 13 ft, so that pretty much covers it.
Is there a simple way to size floor joists? A. Carl Hagstrom responds: The rule of thumb that I like to use when sizing uniformly loaded residential floor joists is "half the span plus two." First, round the clear span of the floor joist up to the nearest foot, and divide by two. Then add two to the answer.
With a 12' deck span, the beam may be either two 2X8's or two 2X10's, depending on the wood used.
As a general guideline, a 2x8 deck beam can typically span up to 10-14 feet when used in residential deck construction. However, it is essential to consult local building regulations and consider factors like live loads, dead loads, and any additional requirements specific to your project.
For residential floor joists made from Southern Yellow Pine or Douglas Fir, a 2×8 can typically span 8 to 10 feet and carry 40 to 50 pounds per square foot of live load. For ceiling joists or roof rafters, a 2×8 may carry about 10 to 15 pounds per square foot of dead load, depending on the span and wood species.
Rules for boring/drilling holes
To start, here's the diagram that comes right out of the codebook. You can put holes in floor joists anywhere along the length of the joist, but you can't put them any closer than 2″ from the top or bottom edge of a joist. The maximum size of a hole is 1/3 the depth of the floor joist.
On BestDeckSite, we recommend installing blocking on 2x8 joists too. Here's a word of caution. As you get on a roll calling out numbers for the guy at the saw while hammering in the preceding block, make sure not to throw off the joist spacing.
A 2×8 is 1.75 inches wider and 1.75 inches deeper than a 2×6. This extra dimension provides greater strength and load-bearing capacity, making it suitable for heavier applications. Strength and Durability: Due to its larger size, a 2×8 typically has a higher load-bearing capacity than a 2×6.
2x8: They're often used for mid-range floors, such as those in living rooms or dining rooms. They can span up to 10 feet and have a higher load-bearing capacity than 2x6 joists.
Commonly used joist sizes are 2-by-6, 2-by-8 and 2-by-10. For example, when you space joists 16″ apart — which is standard for residential decks — a deck spanning 9 1/2′ would require 2-by-6 joists, a 13′ deck would need 2-by-8 joists and a 16′ deck calls for 2-by-10 joists.
The most common lumber sizes for floor joists are 2x6, 2x8, 2x10, and 2x12. Larger joists can span across wider areas. For example, a 2x6 joist would have a 12-foot, 6-inch maximum span, and a 2x10 joist would have a 21-foot maximum span.
2x4 11'-6" 2x6 17'-0" 2x8 21'-8" 2x10 25'-7" 24" O.C.
Deck joist flashing tape is an affordable and effective way to protect your deck's wood substructure. 1. It helps prevent moisture penetration 2. Helps protect lumber from rot 3.
Example: In the joist span table below, the highlighted cell (10-5) indicates that a #2 grade 2" x 8" Douglas Fir joist, spaced 24" apart, can have a maximum span of 10 feet - 5 inches (10-5) if designing for a live load of 40 PSF, a dead load of 10 PSF, and a deflection limit of the total span in inches divided by 360 ...
y Use the Joist Span table to find the acceptable joist sizes for a 12' span, 2x8s at 12” O.C., 2x10s at 16” O.C. or 2x12s at 24” O.C. Use the Beam Size table and find the 8' post spacing column. With a 12' deck span, the beam may be either two 2x8s or two 2x10s, depending on wood used.
30 Feet is a long span (that's almost 10 meters) — assuming it is for a regular residential building, you will need a set of 4″X16″ logs spaced at 20″ minimum. Also, since 16″ deep logs are not easily available, you may have a wood fabricator do it for you; a messy, lengthy and expensive process.
The amount of laminated veneer lumber (LVL) required to span 25 feet will vary depending on the load it will sustain, the distance between supports, and the kind of wood used in the LVL.As a general rule, a minimum LVL size of 5 1/4" x 16" would be needed for a 25-foot span with an evenly distributed load of 40 pounds ...
“A 2×6 spaced 16 inches apart can span a maximum distance of 13 feet 5 inches when used as a rafter, 10 feet 9 inches when used as a joist, and 6 feet 11 inches when used as a deck beam to support joists with a 6-foot span.”
11–7/8″ TJI can easily span that distance. 2″ x 12″ at 16″ o/c can also span that safely.
The span of a 2x6 deck joist depends on your deck joist spacing and material. For instance, a 2x6 redwood or cedar joist can span eight feet at a spacing of 16 inches. On the other hand, a 2x6, 16- or 18-gauge steel joist can span 16 feet, 4 inches if the spacing is 12 inches.