Glossary of Terms

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Term Definition

The weight of materials of construction incorporated into the building, including but not limited to walls, floors, roofs, ceilings, stairways, built-in partitions, finishes, cladding and other similarly incorporated architectural and structural items, and the weight of fixed service equipment, such as cranes, plumbing stacks and risers, electrical feeders, heating, ventilating and air-conditioning systems and automatic sprinkler systems. 

Diagonal brace

A framing member that runs at an angle to other framing members, and with other framing members generally forms a structurally-stable triangular assembly.


A structural assembly comprised of structural sheathing (e.g., plywood, metal cladding) that is fastened to roof, ceiling, floor or floor framing in such a manner that the entire assembly is capable of transferring in-plane shear forces.

Diaphragm chord forces

Chords developing the largest axial forces are often eave and ridge purlins or members near the eave and ridge purlins.

Diaphragm chords

Diaphragm structural framing members that run perpendicular to the applied load, and thus are subjected to axial forces when the load works to bend the diaphragm.

Diaphragm components

When post-frame building components (e.g., purlins, girts, purlin blocks, mechanical fasteners, etc.) are positioned and connected in such a way to form a diaphragm.

Diaphragm structural framing

Primary and secondary framing members to which structural sheathing panels are attached to form a diaphragm assembly. Diaphragm structural framing (1) resists bending moments applied to the diaphragm, (2) helps transfer in-plane shear forces across the diaphragm, and (3) prevents out-of-plane buckling of structural sheathing.


The projecting frame of a recess in a sloping roof.

Double Glazing

An insulating window pane formed of two thicknesses of glass with a sealed air space between them.

Double Hung Windows

Windows with an upper and lower sash, each supported by cords and weights.

Downspout Leader

Downspout A spout or pipe to carry rain water down from a roof or gutters.

Downspout Strap

A piece of metal which secures the downspout to the eaves or wall of a building.

Drag strut

A member, typically horizontal, that transfers shear from a floor, roof or ceiling diaphragm to a shear wall.

Dry Wall

A wall surface of plasterboard or material other than plaster.

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