Reference
Metal building terminology
Most quote mistakes come from four words: span, eave height, ridge height and clear height. Each one measures something different, and only one of them is what a supplier asks for.
Written by Gary Thompson · Steel Building Research EditorSteel Building Research EditorReviewed by Find Steel Buildings Editorial Team
- Terms defined
- 18
- Anchored to
- One labelled section
- Ridge formula
- eave + (span ÷ 2)(rise ÷ 12)
- Excluded
- Loads, spans, sizing
Diagram
One section, every dimension word on it
Ridge height = eave + (span ÷ 2) × (rise ÷ 12). On this section: 14 + (40 ÷ 2) × (4 ÷ 12) = 20.67 ft.
Glossary
What each term measures, and where it appears on a quote
Terms used on steel building quotes
| Term | What it measures | Quote field | Common confusion |
|---|---|---|---|
| Clear span | Width between the inside faces of the sidewall columns, with no interior column | Width | Quoted width is usually the outside dimension, which is slightly larger |
| Eave height | Ground to the point where the sidewall meets the roof line | Height | Confused with ridge height, which is always taller on a gable |
| Ridge height | Ground to the peak of the roof | Not usually asked for; it is derived | Ordering by ridge height gives you a shorter sidewall than expected |
| Clear height | Floor to the lowest overhead obstruction | Door and interior questions | Always less than eave height once framing is in place |
| Bay | Distance between two adjacent main frames along the length | Length | Building length is a whole number of bays, so lengths come in steps |
| Roof pitch | Rise in inches per 12 inches of horizontal run | Roof | Stated as 3:12 rather than in degrees |
| Girt | Horizontal wall member that panels attach to | Not asked for | Mistaken for a structural column |
| Purlin | Horizontal roof member that roof panels attach to | Not asked for | Mistaken for a rafter |
| Rafter | Sloping main frame member carrying the roof | Not asked for | Mistaken for a purlin |
| Column | Vertical main frame member | Not asked for | Interior columns are what a clear span removes |
| Framed opening | A prepared opening for a door or window | Doors and windows | The opening size, not the door size |
| Base angle | Angle section at the base of the wall that panels fasten to | Not asked for | Not the same as the anchor bolts |
| Anchor bolt | Bolt fixing a column base to the foundation | Foundation | Supplied by the building or the concrete contractor, depending on the order |
| Lean-to | Single-slope structure attached to a sidewall | Add-ons | Adds footprint without adding clear span |
| Mezzanine | Intermediate floor inside the building | Interior | Needs clear height, not just eave height |
| Trim | Closure and finish pieces at corners, eaves and openings | Finish | Colour choices are separate from panel colour |
| Panel | The formed steel sheet forming wall or roof surface | Finish | Profile and gauge are separate choices |
| Bay spacing | The chosen distance between main frames | Not asked for directly | Determined by the manufacturer's design, not by the buyer |
Definitions only. This page states no span capacity, member size or load figure.
Practical
The four words that cause most quote errors
Span, eave height, ridge height and clear height all describe size, and only two of them are things you order. You choose the span and the eave height. Ridge height follows from those two plus the pitch. Clear height is what you can actually drive under, and it is always less than the eave height once the frame is in. Answering a supplier with a ridge height when they asked for an eave height produces a building shorter than you wanted.
Limits
What this page deliberately does not cover
Stated planning input
Weighing options
Compare this against the alternative
A side-by-side walkthrough of the decision, written for buyers rather than engineers.
Evidence
Where these numbers come from
Evidence record
- Platform calculation
Roof pitch in degrees = arctan(rise / run)
Computed on this page
- Platform calculation
Ridge height = eave height + (span / 2) x (rise / 12)
Computed on this page
Computed values are recalculated whenever this page renders. Published figures link to the source document. Planning inputs are shown as inputs so you can substitute your own.
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Answers
Common questions
The height from the floor to the point where the sidewall meets the roof line. It is the height figure a supplier asks you to choose, and it is always less than the ridge height on a gable building.
The width between the inside faces of the sidewall columns with no interior column in between. It is what makes an arena or a hangar usable, and it is the figure that moves the price most.
The distance between two adjacent main frames along the length of the building. It is set by the manufacturer's design for your building, not chosen from a table, which is why no numeric recommendation appears on this page.
Ridge height = eave height + (span ÷ 2) × (rise ÷ 12). A 40 ft span at 14 ft eave and 4:12 pitch gives 20.67 ft.
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Related planning topics
Background reading on the questions this page raises. None of these pages sells anything.
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