PEB Building Dimensions: Width, Length and Eave Height

Building dimensions in a pre-engineered building are the reference measurements that define its size and shape: width, length, eave height, bay spacing, roof slope and clear height. They are measured to agreed reference lines, usually the outside of the steel framing, and set the basis for design and pricing.

Key facts

Width is commonly measured between the outside faces of the sidewall girts.
Length is commonly measured between the outside faces of the endwall girts.
Eave height is usually taken from finished floor to the top of the eave strut.
Bay spacing is the center-to-center distance between frames.
Clear height is the usable height under the lowest point of the frame.

How is building width measured?

Width runs across the building, parallel to the frames. In most PEB practice it is measured from the outside of the girts on one sidewall to the outside of the girts on the other, so the wall panels sit just outside that line.

Some projects need the width defined to the column centerlines or to the inside face of a wall. Where this matters, for example to fit a site boundary or racking layout, state the reference line clearly in the inquiry.

Length and bay spacing

Length runs along the ridge, from the outside of the endwall girts at one end to the outside at the other. It is divided into bays by the main frames.

Common bay spacings in industry practice are around 6 to 9 m, though longer bays are possible. End bays are often slightly shorter because of the endwall column offset. The best spacing balances frame weight, purlin size and the layout needs of the building, and is confirmed by the project engineer.

Eave height and clear height

Eave height is usually measured from finished floor level to the top of the eave strut at the sidewall. It controls wall area, frame size and the height available near the walls.

Clear height is often more important to the owner. It is the free height under the lowest part of the frame, the haunch or any hanging equipment, and it decides whether racking, cranes, vehicles or aircraft fit. Give the required clear height and its location rather than only an eave height.

Roof slope and roof shape

Roof slope is the rise over run, often written as 1:10 or 1:20. Low slopes reduce wall height at the ridge and material, while steeper slopes drain faster and may be preferred for appearance or heavy rain.

The roof may be gabled with a central ridge, single slope, or multi-gable with several ridges and valleys. The ridge may also be offset from the center when the site or layout requires it.

Other reference terms

Sidewalls are the long walls parallel to the ridge, and endwalls are the short walls at each end. Frame lines are usually numbered along the length and column lines lettered across the width on the drawings.

Finished floor level is the base elevation for all heights. If the slab is stepped, sloped or has a curb along the walls, show this on the inquiry so the base details and wall panels are set correctly.

Dimensions to state in your RFQ

Width and length with the reference line used.
Eave height and required clear height at critical points.
Preferred bay spacing or any column position limits.
Roof slope and roof shape.
Finished floor level and any curbs or steps.
Positions and sizes of large openings.

Frequently Asked Questions

Is eave height the same as clear height?

No. Eave height is measured to the top of the eave strut at the wall, while clear height is the usable space under the lowest part of the frame, which is usually lower.

Can I choose any bay spacing?

Bay spacing can be adjusted to suit the layout, but it affects frame and purlin sizes and cost. The project engineer will recommend a spacing that balances these factors.

Why are end bays sometimes different?

Endwall columns and girts are offset from the endwall line, and the end frame may be lighter, so end bays are often set slightly shorter to keep purlin spans even.

Engineering content is general guidance. Every World Steel building is designed by qualified engineers to the code and loads of the project.