# Readers ask: Floor Joists In Residential Construction Are Typically What Size?

## 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?

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.

## What size wood is used for floor joists?

Lumber graded as #2 is the most common choice for floor joists and other framing lumber. It has more knots and defects than higher grades, but usually not enough to cause significant loss of bending strength.

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## Can I use 4×2 for floor joists?

4×2 timber floor joists on the ground floor have been used for decades but should be no more than 16 inch or 400 mm centres and be supported at no more than 2 metre centres, 6ft or 1.8 m is preferable and practical.

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

How far can a 2×6 Rafter span without support? The table states that 2 X 6 rafters spaced 16 inches on center (o.c) can span a maximum distance of 13 feet 5 inches.

## 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.

## What is the maximum span of a 2×6 floor joist?

Max. Live Load 30 lbs/ft2 (1436 N/m2)

Maximum Span (ft – in)
Nominal Size (inches) Joist Spacing Center to Center (inches) Lumber Grade
2 x 6 12 12′ – 6′”
16 11′ – 4″
24 9′ – 11″

## How far can a floor joist span without support?

Douglas fir 2-by-10 joists graded as “Structural Select” allows joist spans up to 21 feet for a live load of 30 pounds per square foot when spaced 12 inches apart, 19 feet 1 inch for 16 inch spacing and 16 feet 8 inches for 24 inch spacing.

## How much weight can 2×8 floor joists hold?

A live load of 60 pounds per square foot demands more support and shorter spans. Spaced at 12 inches, the joist may only span 16 feet 8 inches. At 16 inch spacing, 15 feet 2 inches and 13 feet 3 inches at 24 inch spacing.

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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″.

## How do I calculate how many joists I need?

If the joists are placed 16 inches from centers, then multiply the length of wall by Â½ and add 1. This will give the required number. Thus if the wall is 32 feet long, then 32 x Â½ + 1 = 25, he number required for one span.

## What size beam do I need for a 20 span?

you looking around 4×14, 4x 16 for a 20span. i would use a glue lam and not a solid beam ( 1 pc ). steel would be best for strength and space.

## Do I need noggins in floor joists?

If the span of your joists is less than 2.5m then you don’t need to include any noggins. Up to 4.5m span one row of noggins at mid span is needed. Above 4.5m span use two rows of noggins at third points. Noggins need to be at least 38mm wide and the depth should be at least 0.75 times depth of joists.

## How much weight can a 2 by 6 hold?

The weight that can be supported by a double or triple wood header

Span (feet) Weight Supported (lb)
2 x 2” x 6 2 x 2” x 10″
6 1680 5000
8 3760
10 3010

## How do you calculate floor joists?

The basic math is to divide the width by the on center spacing, round up to the nearest integer and then add one for the first joist (at the zero position). The length is used for the length of the joists or I-joists.