I-Joist Count

Last modified by

RitaHegeman

on

Jan 28, 2025, 7:49:58 PM

Created by

KurtHeckman

on

Apr 7, 2014, 2:25:51 PM

`"iJC" = (( W *12) / ( 16 ) + 1) +"adder"`

Toggle Units

`(W)"Floor Width"`

ft

in

`(oC) "On-center Spacing"`

NOTES

This algorithm makes no assumptions for the maximum span. It is assumed that joist of the appropriate span can be found (steel, I-joists, or other materials). This equations only provides the number of the spanning joists (brown-red in diagram) and not those on the very edges (e.g. first and last plates). See diagram. It does assume that the first and last i-joist are right next to the edge plates.

An I-joist, also known as engineered wood I-beams, is a type of engineered wood product commonly used in residential and commercial construction for floor and roof framing. It consists of a combination of solid lumber flanges or chords, typically made of either laminated veneer lumber (LVL) or dimensional lumber, and a web made of oriented strand board (OSB) or plywood.

The I-joist design provides several advantages over traditional solid wood joists, including increased strength-to-weight ratio, dimensional stability, and resistance to warping, twisting, and shrinking. They are also designed to resist bending and deflection, making them suitable for longer spans than traditional joists.

Overall, I-joists offer versatility, strength, and cost-effectiveness, which have made them a popular choice in modern construction projects.

Joist Calculators

Floor Joist Count: Computes the number of joists (joists and end plates) and joist ties required for a floor or deck based on the dimension of the room or deck and the on-center joist separation.
Floor Joist Cost: Estimates the cost of Floor Joist boards (joists and end plates) required for a floor or deck based on the dimensions of the deck, spacing of joists and unit cost of joist boards.
Joist Hanger Count: Computes the number of joist hangers required for a deck based on the width of the deck and the spacing of joists.
I-Joist Count: Computes the the number of I-Joist boards required to cover a span (width) based on the size of the span and spacing of the I-Joists.
Maximum Joist Span: Computes the span length of a (1,200 pounds per square inch fiber stress) wood joist based on the live load, spacing, board width (e.g., 2x6 vs 2x10) and whether the joist need to be extra stiff for materials attached such as plaster below them.
Joists on Beams: Computes the number of joists (2x dimensional lumber or i-joists), number of beams, number of joist hangers, and length of plate boards needed for a floor or deck with a span that might require one or more beams.
On Center Spacing: Computes the even spacing between a number of objects (e.g. posts, studs, joists, rafters, trusses, lights, rebars) over a specified length or distance.