Floor joist: spacing, sizes and span | floor joist spacing | floor joist sizes | 2×6 floor joist span | 2×8 floor joist span | 2×10 floor joist span | 2×12 floor joist span.
Floor joists can be define as several small beams. Floor joists are typically a horizontal structural member that runs across an open space of building on supporting wall or studs. Their function is similar as beams, except floor joists are supported by wall, foundations, or beams framing.
Floor joists usually run between walls or rafters to support a ceiling or floor. They transfer the dead load of the subfloor and floor finishes and live load of people, furniture and furnishings to beams, walls, headers, or foundation walls. It is like the skeleton/ framing of a building that supports the load which the floor is built to bear. Joists are technically beams that typically spans relatively short distances compared to beams and are made of wood, steel, or engineered wood or lumber.
There are different sizes of floor joist are used in floor construction such as 2×6, 2×8, 2×10 and 2×12, made of different species of wood (southern yellow pine & Douglas fir) and different grade such as grade – 1, grade – 2, grade – 3. Southern yellow pine is strongest species of wood that can span more distance compared to other species of wood. Grade 1 lumber have higher strength than other grade Lumber due to fewer knots.
Floor joist: spacing, sizes and span
What is a floor joist?, A floor joist is a part of a floor system that acts as a beam structure, supporting the load acting upon the attached flooring material. In a floor system, we use several floor joists properly spaced from each other, so that subflooring materials like plywood or wooden planks are safe to walk on.
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As per international residential code, most standard, floor joist spacing is 16 inches apart on centre (12″, or 24″ apart on centre also being used) and bearing size of 2″×6″ to 2″×12″, which can span 10 feet to 20 feet.
Floor joist sizes
As per international residential code, the typical floor joist sizes used in construction are 2″×8″ (2 by 8), 2″×6″ (2 by 6), 2″×10″ (2 by 10), and 2″×12″ (2 by 12), but most common and standard one is 2×8. However, dimensions such as 2″×10″ and 2″×12″ are best suitable for longer spans. On the other hand, floor joist systems can also use 2″×4″ and 2″ × 6″ for small-sized floor areas.
Floor joist spacing
Most standard, floor joist spacing is 16 inches apart on center, but this can vary depending on building codes and the requirements of the structure. So, 12 inches, and 24 inches apart on centre are also used. Floor joists help distribute the load of a structure. The joist which are kept at lower spacing can allow longer distance to span as compared to joist spaced further apart.
Floor joist span
Floor joist span is the distance that a structural member such as a joist can span, from one end to the opposite end. A variety of factors play into joist span, including but not limited to: distance covered, width and thickness of the joist, type of material, and spacing between the joists
How far can a 2×6 floor joist span without support?
As per international residential code, A select structural grade Douglas Fir-Larch floor joist with a nominal size of 2″×6″ can span to about 10 feet 9 inches long (supported only at both ends) without support with a maximum load of 50 psf at standard 16-inch spacing.
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How far can a 2×8 floor joist span without support
As per international residential code, A select structural grade southern pine floor joist with a nominal size of 2″×8″ can span to about 12 feet 0 inches long (supported only at both ends) without support with a maximum load of 50 psf at standard 16-inch spacing.
How far can a 2×10 floor joist apan without support
As per international residential code, A select structural grade southern pine floor joist with a nominal size of 2″×10″ can span to about 16 feet 0 inches long (supported only at both ends) without support with a maximum load of 50 psf at standard 16-inch spacing.
How far can a 2×12 floor joist span without support
As per international residential code, A select structural grade southern pine floor joist with a nominal size of 2″×12″ can span to about 18 feet to 20 feet long (supported only at both ends) without support with a maximum load of 50 psf at standard 16-inch spacing.
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Conclusion:
A floor joist is a part of a floor system that acts as a beam structure, most standard, floor joist spacing is 16 inches apart on centre and bearing size of 2″×6″ to 2″×12″, which can span 10 feet to 20 feet.