I-Joist Glossary

Backer Block

Blocks made from lumber or wood structural panels that are attached to the web of an I-Joist to develop the design capacities of the fasteners used in the web.

Bearing Stiffener

See web stiffener.

Blocking Panel

Short length, full depth section of wood I-Joist or APA EWS Rim Board that are cut to fit between floor joists. Blocking panels prevent the floor joists from overturning and distribute vertical and lateral loads through the floor system into the structure below.

Cripple Block

See Squash Block.

EWS

Stands for Engineered Wood Systems, a related corporation of APA.

Filler Block

Filler material made of lumber and/or wood structural panels placed between the webs of adjacent I-Joists. The webs of the adjacent I-Joists are nailed to the filler blocks to provide load sharing between the joists.

Flange

The top and bottom pieces of a wood I-Joist which are comprised of solid-sawn lumber or structural composite lumber.

Hanger Bracket

A metal shoe fixed to the wall into which an I-Joist sits.

I-Joist

An 'I'shaped engineered wood structural member designed for use in residential floor construction. The product is prefabricated using sawn or structural composite lumber flanges and wood structural panel webs, bonded together with exterior adhesives.

Joist Designation

A means of identifying an I-Joist by reference to its depth in inches followed by the letters PRI and a number which relates to the joist strength and stiffness e.g. 9-1/2" PRI-30.

Knockouts

Prescored holes often provided by I-Joist manufacturers for the contractors convenience to install electrical or small plumbing lines. They are typically 35 - 45 mm in diameter and spaced 300 to 600 mm on centre along the length of the I-Joist.

Load-Bearing Wall

A wall that transfers any load, vertical or lateral, in addition to its own weight into the structure below.

Load Stiffener

See web stiffener.

PRI

Stands for Performance Rated I-Joist.

PRI - 400

Name of the APA EWS Performance Standard for I-Joist manufacture.

Multiple Span

A situation where a horizontal load-carrying element is placed continuously over three or more supports.

Rim Board

A glued engineered wood product that is attached continuously to the ends of the floor joists, preventing overturning of the joist. Rim boards also complete the 'weathering-in' of the floor system and transfer both vertical and lateral loads.

Simple Span

A situation where a horizontal load-carrying element spans between two supports.

Squash Block

Sawn lumber members or sections of APA Rim Board that are nailed to each side of an I-Joist at the location of concentrated loads. Sawn lumber squash blocks are cut 1.5 mm (1/16") longer than the I-Joist depth to ensure that the load is transferred by the squash block around the I-Joist to the support directly below.

Structural Composite Lumber (SCL)

Lumber manufactured by parallel orientation of wood fibres of various geometries, bonded with a structural adhesive. Most commonly, this takes the form of laminated veneer lumber (LVL).

Web

The vertical element of a wood I-Joist that is made of plywood or OSB. The web joins the top and bottom flanges of the I-Joist and transmits shear forces.

Web Hole

Aperture cut in the web to facilitate the passage of services. The size, position and number of the holes relative to each must be strictly controlled.

Web Stiffener

Wood structural panel or sawn lumber members placed between the flanges of I-Joists in locations where increased reaction capacity (bearing stiffener) or concentrated load carrying capacity (load stiffener) of the I-Joist is required. Web stiffeners are cut 3 mm (1/8") less than the dimension between the flanges and placed tightly against the flange resisting the applied load. (Generally, the bottom flanges for bearing stiffeners and the top for load stiffeners.)