Purlin vs. Joist

Purlinnoun

A longitudinal structural member bridging two or more rafters of a roof.

Purlinnoun

In root construction, a horizontal member supported on the principals and supporting the common rafters.

Purlin

A purlin (or historically purline, purloyne, purling, perling) is a longitudinal, horizontal, structural member in a roof. In traditional timber framing there are three basic types of purlin: purlin plate, principal purlin, and common purlin.

Joistnoun

A piece of timber laid horizontally, or nearly so, to which the planks of the floor, or the laths or furring strips of a ceiling, are nailed.

Joistverb

(transitive) To fit or furnish with joists.

Joistnoun

A piece of timber laid horizontally, or nearly so, to which the planks of the floor, or the laths or furring strips of a ceiling, are nailed; - called, according to its position or use, binding joist, bridging joist, ceiling joist, trimming joist, etc. See Illust. of Double-framed floor, under Double, a.

Joistverb

To fit or furnish with joists.

Joistnoun

beam used to support floors or roofs

Joist

A joist is a horizontal structural member used in framing to span an open space, often between beams that subsequently transfer loads to vertical members. When incorporated into a floor framing system, joists serve to provide stiffness to the subfloor sheathing, allowing it to function as a horizontal diaphragm.