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How do I know what size floor joists I need?
For example, assume the clear span is 15 feet 6 inches. Round up to 16 and divide this span by 2, giving you 8. Next, add 2 to get the required joist depth. In this example, 8 + 2 = 10, so a 2×12 floor joist will be required (it’s important to use the actual lumber dimensions, not the nominal dimensions).
What is the minimum joist size?
Typical Floor Joist Size In Residential Construction Floor joists range from 2×8 to 2×12. It is less common to see joists that are 2×6, even though they are included in joist span tables. Older homes are more likely to use 2×6 for joist framing.
How thick should floor joists be?
Joists in home construction are usually made with 2-by-10 or 2-by-12 lumber, which are 9 1/4 and 11 1/4 inches deep, respectively.
How far can a 2×6 ceiling joist span?
The maximum distance a 2×6 can span, according to the 2018 IRC, for a floor joist, is 12′-6”, ceiling joist 20′-8”, rafter 18′-0”, deck board 24”, deck joist 9′-11”, deck beam 8′-3”, and 6′-1” as for header. Always check the codes for determining factors or consult a Structural Engineer.
How much can you notch a 2×8 floor joist?
Maximum notch depth in the outer third of a joist is one-sixth of the joist depth. Limit the length of notches to one-third of the joist depth. No notching in the middle third of a joist.
How big of a hole can I cut in a 2×10 floor joist?
The maximum allowable diameter of a hole in any solid-lumber joist is one-third of the joist’s depth. Notches can’t be deeper than one-sixth of the joist depth. In the case of your 2×10 joists, the maximum diameter is 35⁄64 in. (91⁄4 in.
How thick should ceiling joists be?
Standard Size of Joists Though there is no standard joist size for the ceilings in all buildings, most average homes use ceiling joists in a board size of 2-by-6 inches. The range of joist sizes used in homes varies though, between 2-by-4 inches and 2-by-12 inches.