Post-Frame Construction Glossary

A

Accessory: An extra building product.
Agricultural Building: A structure designed and constructed to house farming implements, hay, grain, poultry, livestock, or other horticultural products.
Attic: The space between the ceiling beams (or joists) of the top story and the roof rafters (or purlins).
Awning: An architectural projection providing weather protection, identity, or decoration that is wholly supported by the building to which it is attached — comprised of a lightweight, rigid skeleton structure over which a covering is attached.

B

B Exposure: Urban and suburban areas, wooded areas, or other terrain with numerous closely spaced obstructions the size of single-family dwellings or larger. Exposure B is assumed unless the site meets the definition of another exposure type.
Bay: The distance between adjacent mainframe (post-frame) centerlines or primary supporting members along the length of the building, measured parallel to the ridge.
Beam: A structural member, usually horizontal, used for support in a building and subjected to bending loads.
Beam and Column: A structural system of rafter beams supported by columns, often used in animal "stall" or "grid" barns.
Bearing Block: A dimensional lumber block placed beneath roof trusses, rafters, or beams and fastened to a support column to provide extra support for vertical loads.
Bearing Height: The vertical distance between a pre-defined baseline (generally the grade line) and the bearing point of a component.
Bottom Chord: An inclined or horizontal member establishing the bottom of a roof truss.
Bottom Girt (Splash Board): Pressure-treated lumber installed at the grade line to which the bottom of the building siding is normally attached.
Brace: A piece of structural material, temporary or permanent, that strengthens another member or holds it in place.
Bridging: Structural blocking used to give weak-axis stability to floor joists or roof purlins.
Building Code: Regulations established by a recognized agency describing design loads, procedures, and construction details for structures, usually applied within a designated jurisdiction (city, county, state, etc.).
Building Level (Transit): A surveyor's instrument with a horizontally mounted telescope, used to determine a level point or points.

C

Camber: A predetermined curvature designed into a structural member to offset anticipated deflection when loads are applied.
Cantilever: A beam or column supported only at one end. A sidewall column of a roof-only structure is a cantilevered pole; a roof purlin extending beyond the gable endwall to support an overhang is also cantilevered.
Ceiling Joists: Secondary horizontal framing members attached between the bottom chords of trusses, used to attach gypsum wallboard or other ceiling finishes.
Check: Separation of the wood usually extending across the annual growth rings, commonly resulting from stresses built up during seasoning.
Chords: An inclined or horizontal member establishing the top or bottom of a roof truss (top chord or bottom chord).
Cladding (Building Skin): The exterior covering of a building.
Clear Height: The vertical distance between the finished floor and the lowest part of a truss, rafter, or girder — not the same as eave height.
Clear Span: The clear distance between adjacent supports of a horizontal or inclined member.
Closure Strip: A resilient strip formed to the contour of ribbed panels, used to close openings created where metal panels join other components — typically used under ridge caps.
Column: A primary vertical structural member that transfers loads from roof beams, rafters, or trusses to the foundation, generally partly embedded in the soil for lateral and vertical support.
Concrete Collar: Concrete placed into a pre-bored hole around a structural building column to provide superior resistance to wind uplift forces; depth is specified by the engineer of record.
Continuity: The transfer of loads and stresses from member to member in a structural system as if there were no connections.
Corner Post: An end wall column located at the corner of the building.

D

Dead Load: The vertical gravity load from the combined weight of all permanent structural and non-structural components of a building — constant in magnitude and location throughout the building's life.
Deck: An exterior floor supported on at least two opposing sides by an adjacent structure and/or posts, piers, or other independent supports.
Deflection: The displacement of a structural member under load. Deflection limits are less critical for unfinished post-frame buildings but must be considered for finished buildings with gypsum wallboard, etc.
Design Loads: Loads specified by building codes for use in design, including snow, wind, seismic, and dead loads.
Design Strength: The product of the nominal strength and a resistance (or strength reduction) factor.
Dimensional Lumber: Wood members from two nominal inches to, but not including, five nominal inches in thickness, and two or more nominal inches in width.
Door Guide: An angle or channel guide used to stabilize or keep plumb a sliding or rolling door during operation.
Dual Pitch Roof: A gabled roof system where the slope on one side is steeper than the other.
Duration of Load: The period of continuous application of a given load, or the aggregate of periods of intermittent applications of the same load.
Dynamic Loads: Loads resulting from the dynamic effect of cranes, hoists, and materials handling equipment.

E

Eave: The line along the sidewall formed by the intersection of the wall and roof planes, where the sidewall and roof meet.
Eave Girts (Eave Purlins): Horizontal secondary framing members attached at sidewall columns at the eave, supporting wall coverings and/or the lower edge of the roof cladding.
Eave Height: The vertical distance from the bottom of the skirt board to the eave.
Eave Lights: Fiberglass-reinforced panels (FRP), typically matching the sidewall steel's rib configuration, placed near the top of the sidewalls below the eave to allow natural light in.
Eave Vents: Perforated enclosed soffits that allow airflow into the building, working with a vented ridge to release warm, moist air.
Elevated Floor (Loft): A second-story wood floor, normally plywood, supported by beams and joists.
End Bay: The bay adjacent to the end wall of a building, usually measured from the end wall to the first interior primary frame.
End Rafter: Dimensional lumber used to support the vertical roof load between endwall wind columns.
Endwall: An exterior wall perpendicular to the ridge of the building; on a peaked or gabled roof, this wall has a "point."
Endwall Diaphragm: The endwall of a building constructed so the cladding and framing transfer in-plane shear forces from the roof and/or ceiling to the ground.
Endwall Overhang: The projection of the roof past the endwall.
Endwall Wind Columns: Primary vertical structural members of the building endwalls that transfer loads from endwall roof beams, rafters, or trusses to the foundation.
Entry Door (Man Door / Walk Door): A pre-hung, hinged door for building access, most commonly 36 inches wide by 6'8" tall.

F

Fascia: The flat surface located at the outer end of a sidewall roof overhang or cantilevered end.
Fastest-Mile Wind Speed: The highest sustained average wind speed, based on the time required for a mile-long sample of air to pass a fixed point, per NOAA wind velocity maps.
Ferric Oxide: A chemical compound that produces a rust-like color, historically used in red paint — one reason many Mid-Atlantic barns and post-frame structures were traditionally painted red.
Fill: Material used to raise the level of a grade.
Fire Wall: A fire-resistance-rated wall with protected openings that restricts the spread of fire and extends continuously from the foundation to or through the roof.
Flashing: Sheet metal or plastic components used at breaks and openings in walls and roofs to ensure weather-tightness and enhance appearance.
Footing: Concrete placed under a structural column, wall, or other member to transfer loads to the soil over a greater area — usually not required when column holes are backfilled with concrete.
Foundation: The substructure that supports a building or other structure.
Frame: The primary structural members (columns and rafters) that support the secondary framing.
Frame Spacing: The horizontal distance between post-frames, generally equated to the distance between adjacent trusses or rafters.
Framed Openings: Jambs, headers, and flashing surrounding an opening in the wall of a building.
Full Hip Roof: A roof without gables that rises by inclined planes from all four sides of a building, sloping toward every wall.

G

Gable: The triangular portion of the endwall above the eave line on a roof system with a peaked end.
Gable Roof: A ridged roof terminating in gables, with one slope of equal pitch on each side.
Galvanized: Steel coated with zinc for corrosion resistance.
Gambrel Roof: The traditional "barn style" roof, similar to a gable roof but with a pitch change from steep at the eaves to a lesser slope near the ridge — often allows for usable attic space.
Girts: Horizontal secondary framing members attached to endwall or sidewall columns to support wall coverings and distribute wind-induced wall loads to the post frame.
Glued-Laminated (Glu-Lam) Timber: A structural timber made of assemblies of selected wood laminations with parallel grain, bonded together with adhesives.
Grade: The ground elevation around a building.
Grade Line (Grade Level): The line of intersection between the building exterior and the top of the soil, gravel, or pavement in contact with it.

H

Headers: Structural framing members supporting the ends of members cut short by a floor, wall, ceiling, or roof opening — commonly used over wide sidewall door openings.

I

IBC: International Building Code — a unified national building code first published in 2000, based on years of experience from prior national code organizations.
Inspections: The review of construction work by a building official where a permit is required. Typical post-frame inspections include hole, framing, and final inspections.
Insulation: Any material used in construction to reduce heat transfer.
Interior Clearance: The vertical distance from the top of a finished floor to the bottom of the roof trusses.
Intermediate Bay: The distance between two primary frames within a building, other than the end frames.

J

Jamb: A vertical framing member located at the side of an opening.
Joist: Lumber arranged parallel from wall to wall (or truss to truss) to support a floor or ceiling.
Joist Hanger: An engineered metal bracket that supports a member, such as a purlin, from the side of a second member, such as a truss or rafter.

K

Knee Braces: Inclined diagonal lumber braces connecting sidewall columns to roof trusses, intended to supplement lateral wind resistance in post frames.

L

Laminated Veneer Lumber (LVL): A structural composite lumber assembly made by gluing together wood veneer sheets with parallel wood fibers.
Lean-To: A structure with only one slope that depends on another structure for partial support.
Live Loads: Static and dynamic loads resulting from a building's use and occupancy, excluding construction or environmental loads.
Loads: Forces or actions on structural systems from permanent construction, occupants, environmental effects, and other sources.
Lockset: A door knob and locking mechanism.
Lumber Grade: The classification of lumber by strength and utility per an approved grading agency's rules.

M

Machine Graded Lumber: Lumber evaluated by machine using nondestructive testing, followed by visual grading for characteristics the machine cannot evaluate.
Manufactured Component: A component assembled in a manufacturing facility, such as pre-fabricated wood trusses or laminated columns.
Masonry: Anything constructed of bricks, concrete blocks, ceramic blocks, or concrete.
Metal Cladding: Metal exterior and interior coverings, usually cold-formed steel sheeting, fastened to the structural framing.
Mezzanine: An intermediate floor placed within a story or room.
Monolithic Construction: Pouring the concrete grade beam and floor slab together as one foundation, rather than separately.
MSR (Machine Stress Rated): Lumber that is non-destructively tested for strength mechanically, providing more consistent strength than visually graded lumber.

O

O.C. (On Center): The distance between the centers of two members.
Open Bays: Portions of walls without cladding, doors, or other permanent coverings.
Oriented Strand Board (OSB): Structural wood panels manufactured from reconstituted, mechanically oriented wood strands bonded with resin under heat and pressure.
Overhead Door: A door on vertical tracks that opens upward, becoming parallel with the floor and above the opening.

P

Panels: Sheet metal, usually ribbed, used for roof and wall skin.
Peak (Ridge): The highest point of the roof, describing a horizontal line running the length of the building.
Pitch: The rise or angle of the roof, stated in inches of rise per twelve inches of horizontal run.
Plywood: A built-up panel of laminated wood veneers, with grain orientations typically at 90 degrees to each other.
Pole: A round, unsawn, naturally tapered post.
Post (Column): A vertical primary structural member that transfers loads from beams, rafters, or trusses to the foundation.
Post Frame: A structural building frame consisting of a wood roof truss or rafters connected to vertical timber columns or sidewall posts.
Post Frame Building: A building system whose primary framing is principally comprised of post frames.
Pressure Preservative Treated Wood: Wood pressure-impregnated with an approved preservative chemical under approved treatment and quality control.
Purlin: A secondary horizontal framing member attached to roof rafters or trusses, laterally supporting them and transferring loads between cladding and structure.

R

Rafter: A sloping roof framing member.
Rake: The part of a roof projecting over the endwalls, or the line formed by the wall/roof intersection where there is no overhang.
Ridge Cap: A transition of roofing materials along the ridge of a roof.
Roof Live Load: Loads induced by building use and occupancy, excluding wind, snow, seismic, or dead loads.
Roof Snow Load: The vertical load from snow weight applied to the horizontal projection of a roof, influenced by slope, temperature, and wind exposure.
Roof Truss: An engineered structural roof support member made of three or more members carrying tension or compression forces, assembled into triangular patterns.

S

Scissor Truss: A roof truss with a bottom chord sloping upward to an interior peak, allowing for increased interior clearance near the center of the building.
Screeding: The process of striking off excess concrete to bring the surface to the proper finish and elevation.
Sheathing: OSB, plywood, or steel roof covering that transfers roof loads to purlins, rafters, and/or trusses.
Skirt Boards (Splash Boards): Pressure-treated lumber installed at the grade line to which the bottom of the siding is attached.
Sliding Door: A door with a metal frame and steel skin that moves horizontally along a building face, common in agricultural or animal confinement buildings.
Soffit: The underside covering of roof overhangs or mansards.
Span: The horizontal distance between two points.
Stud: A vertical wall member to which exterior or interior covering may be attached, either load-bearing or non-load-bearing.

T

Tensile Strength: The longitudinal pulling stress a material can bear without tearing apart.
Timber: Wood members five or more nominal inches in the least dimension.
Top Chord: An inclined or horizontal member establishing the top of a truss.
Trim (Flashing): Light-gauge metal used to cover exposed edges of steel cladding, especially around openings and intersections.

U

UBC (Uniform Building Code): A code dedicated to better building construction and greater public safety through uniform building laws.
Uplift: Wind loading on a building that causes a load in the upward direction.

V

Vaulted Truss: See Scissor Truss — a roof truss allowing for increased clearance near the center of a building.
Vented Ridge: A ridge design that allows warm, moist air to escape through the peak of the building, provided adequate air intake (gable or eave vents) is present.
Ventilation: The natural or mechanical process of supplying or removing air from a space.

W

Wainscot: Material on the lower few feet of a wall, divided from the upper portion — primarily an aesthetic feature, though steel wainscot panels are easy to replace if damaged.
Web: A structural member joining the top and bottom chords of a truss, forming its triangular patterns.
Wind Loads: Loads from wind coming from any horizontal direction.

Z

Zinc-Aluminum Coated: Steel coated with zinc and aluminum for corrosion resistance, sometimes sold under trade names like Galvalume or Zincalume.

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