Home | Pole Building Basics | Pole Building FAQs  | Pole Building Terminology | Engineering Order Form  |  Contact

A Few Pole Building Terms
The following are a few of the most common Pole Building terms used by builders and engineers. Of course, if you come upon a term you don’t understand that is not in the glossary below, or you have other questions, please feel free to call us anytime!

Have a specific question about your pole building?
Call (503) 302-7020
during regular business hours (PST) to speak directly with a licensed engineer about your project free of charge!

Backfill - Material used to fill a posthole, typically concrete or crushed gravel.

Cladding - The metal exterior and interior coverings fastened to the purlins and girts (see also: sheathing).

Corbel Block or Bearing Block - A piece of dimensional lumber installed vertically under the heel of a truss or rafter and attached to the post with nails, screws or bolts to provide vertical support for the rafter or truss.

Diaphragm - A structural assembly comprised of metal cladding or wood sheathing fastened to roof or wall framing with multiple fasteners capable of transferring in-plane shear forces.

Eave height - The height of the eave wall measured from grade to the top of the top eave girt.

Eave wall - The wall on the side running perpendicular to the main trusses or rafters.

Embedment - The portion of the post that is buried in the ground and backfilled with either concrete or crushed gravel.

Gabled roof - A typical roof (the most common) sloping down each side from a ridge running parallel with the eave wall.

Gable wall - The triangular end wall of a gabled roof building.

Gambrel roof - A roof with two slopes on each side of the ridge, the lower slope being steeper than the upper slope.

Girt - A structural member spanning horizontally between wall posts or columns to provide structural support for posts and attachment for wall cladding or sheathing.  They can be installed flat against the back of the post or like a shelf and installed between the posts (commercial style).

Heel - The end of a truss or rafter that is attached to a post or beam for support


Dead load - Loads resulting from permanent loads due to the weight of the building structure itself or permanently installed equipment & components.

Live load - Loads resulting from temporary loads due to wind, snow, seismic, people and other loads that may not be imposed continually on the structure.

Monoslope - A roof with a single slope from one side of the roof to the other, also called a “shed roof”.

O.C. - Stands for “on-center”, specifying structural member spacing with respect to each other and measured from the center of the members (i.e., 24” o.c.).

OSB - Stands for Oriented Strand Board-Structural wood panels similar to plywood but manufactured from wood strands resembling wood “patches” bonded via heat and pressure.

Outrigger - A member that matches the purlin size and grade placed perpendicular to purlins on top of the truss top chord or rafter at the eave wall post, and extends out past the wall to provide support for the roof overhang.

Post or Pole - A vertical column typically providing significant structural vertical and lateral support.  They are used in post frame construction to transfer loads from main roof beams, trusses or rafters to the foundation.  Posts are typically rectangular and uniform in shape, while poles are typically round (however both are used interchangeably).

Posthole - The hole in which the structural posts of a pole building are embedded providing lateral support for the building.

Post pad - The concrete pad (typically 6” thick) at the bottom of the posthole to provide vertical support for the post and distribute the vertical load to the soil.

Pressure treated wood - Wood that has been chemically treated under pressure to provide resistance to damage from rot, decay and insects.

Purlin - A structural member spanning horizontally between the truss top chords or rafters used to support roof sheathing.

Purlin block-Blocking placed between truss top chords or rafters that extend up to provide attachment and lateral support for purlins on top of the trusses or rafters.

Rafter - A main roof framing member, typically supporting a purlin or can directly support roof sheathing depending on the building configuration.

Sheathing - Structural (or non-structural) panels used for roof and wall covering.  Sheathing is typically plywood or OSB but can also apply to metal sheathing (aka “cladding”).

Skirt Board - The bottommost pressure-treated wall girt next to the ground at grade line providing an attachment point for the bottom of the wall cladding

Snow drift - Additional snow load usually on a lower roof, resulting from additional snow blowing against a wall above a roof, or snow sliding off of an upper roof onto a lower roof.

Top eave girt - The top girt/purlin at the top of the eave wall, providing attachment for the top of the wall sheathing and also for the roof sheathing at the top of the wall.

Truss - A structural component (typically engineered) assembled from smaller wood or steel members and mechanical fasteners designed to carry high loads across long spans, typically utilizing a configuration of multiple triangles.

Uplift - The load on a building component resulting in an upward force, typically from wind load or from the ground in the form of groundwater or frost heave.

Ph. (503) 302-7020
Fax (888) 535-6341

South Valley Engineering
4742 Liberty Rd S #151
Salem, OR 97302

Back to top

All Rights Reserved South Valley Engineering 2014-Present

Web Design by LadyWebPro.com