What size are floor joists in residential construction?

Looking at this table you will see there is a choice in the size of floor joist (2 X 6, 2 X 8, 2 X 10 or 2 X 12) and there is a choice in the joist spacing (12″, 16″ or 14″). The floor joist spacing is the distance between the centers of any two installed joists.

What size should floor joists be?

The spacing of floor joists is just one of the components used to determine the minimum size of the floor joist. Per the prescriptive tables found in Chapter 5 of the International Residential Code (IRC), the standard floor joist spacing used is 12, 16, 19.2, and 24 inches on center.

What is the minimum size of a floor joist?

3.2. Floor joists shall have a bearing support length of not less than 11/2 inches (38 mm) for exterior wall supports and 31/2 inches (89 mm) for interior wall supports. Tracks shall be not less than 33 mils (0.84 mm) thick except where used as part of a floor header or trimmer in accordance with Section R505. 3.8.

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What size wood is used for floor joists?

Lumber graded as #2 is the most common choice for floor joists and other framing lumber.

Can I use 2×6 for floor joists?

How do I keep them even? In general terms, joists spaced 16 inches on center can span 1.5 times in feet their depth in inches. A 2×8 up to 12 feet; 2×10 to 15 feet and 2×12 to 18 feet. 2×6 joists should only be used on ground-level decks that do not require, and will not provide for, any guards.

How far can a 2×6 joist span without support?

2-grade 2×6 joists can span up to 10 feet 9 inches from beam to beam when spaced the standard 16 inches apart with a maximum live load of 30 inches per square foot. In comparison, No. -1 grade lumber can span slightly further to 10 feet 11 inches under the same parameters.

How much weight can a 2×6 floor joist hold?

The larger the deck, the larger the joists. how much weight will a 2×6 floor hold? For example, a properly designed office floor can support 50 pounds per square foot. This may seem light, but this is 50 pounds over each and every square foot of floor space.

What size floor joist do I need for a 14 foot span?

Max. Live Load 60 lbs/ft2 (2873 N/m2)

Maximum Span ( ft – in)
Nominal Size (inches) Joist Spacing Center to Center (inches) Lumber Grade
2 x 12 24 13′ – 2″
2 x 14 12 20′ – 10″
16 18′ – 0″


How do I calculate how many joists I need?

To estimate them 12 inches from centers add 1 to the number of feet in length of one wall on which the joists are placed. For example, suppose a building is 32 feet long, and the joists are placed 12 inches from centers. We simply add 1 to 32, which makes 33 the number of joists required for one span.

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What is code for floor joist?

Floor Joist Building Code Requirements The joist must have a minimum of 1 1/2″ riding on the wall or beam. If the joists are lapped, then they must be lapped at least 3″. Maximum end notches for 2 x 8, 2 x 10, and 2 x 12 respectively are 1 13/16″, 2 5/16″, and 2 13/16″.

What goes under floor joists?

What Is a Subfloor? Subflooring provides a base for finish flooring and also serves as a platform during construction. It may be made of boards laid either at right angles or diagonally across joists. Or the subfloor may be made of plywood or other panel products that are laid perpendicular to the joists.

Can I use 2×4 for floor joists?

for a real house no you cannot, 2×4 will not have the structural strength to support a load as a floor house in a house. There are also 2×4 truses that are used as floor joists. Floor joists are normally 2×12 so all the floors are the proper height.

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