Steel portal frames are among the most commonly used structural systems in the UK for industrial units, agricultural sheds, warehouses, and commercial buildings. Their durability, speed of construction, and wide open spans make them an intelligent, cost-effective solution to today’s construction projects.
This guide covers how portal frames work, why they’re used so extensively, and what to look out for when specifying one for your next project.
What Is a Steel Portal Frame?
A steel portal frame is a structure made of steel rafters and columns joined by rigid connections. Unlike plain post-and-beam buildings, rafters and columns in a portal frame both support lateral loads and bending simultaneously. The result is a strong, stable frame with no need for internal support walls.
The ‘portal’ aspect is the ability to create vast open areas — perfect for buildings where openness and plan flexibility are considerations.
How Do Steel Portal Frames Work?
A portal frame’s stability comes from its fixed joints. These allow the entire frame to withstand vertical and horizontal loads, for example, wind or roofing material. Loads are transferred to the building by reducing the number of columns inside.
Most portal frames are clad in metal cladding or other external skins. The steel bears the burden of the structure, and the external skins are only there for decorative purposes and to add weather protection and insulation.
Principal Benefits of Steel Portal Frames
- Rapid Build Time
Steel portal frame members are manufactured in factories off-site and bolted together on-site, conserving labour time and eradicating delays.
- Cost Savings
In relation to masonry construction or concrete, portal frames need less material and less foundation work. This keeps overall costs of construction lower — especially for large buildings.
- Free Internal Spans
Portal frames do not need internal support columns to span vast areas. This is appropriate for uses like storage, manufacturing, or sports where uninterrupted floor space is essential.
*4. High Strength and Durability
Steel can hold heavy loads and will not warp or crack. Treated steel also will last decades with minimal upkeep and can withstand harsh weather conditions.
- Flexible Designs
Portal frames are easily designed to accommodate a wide range of widths, heights, and roof pitches. They are also easy to add on to in the future if the building needs to be expanded.
- Recyclable Materials
Steel is one of the greenest building materials used. Frames use largely recycled steel and are repurposed or reused at end-of-life.
General Uses of Steel Portal Frames
Steel portal frames are used in a wide range of industries, including:
Warehouses – owing to their large clear spans and low cost of build
Agriculture – barns, grain stores, and machinery sheds value robust frames and easy access
Workshops – cheap to heat, simple to insulate and add on as needed
Sports Halls – open internal area with few or no supports or pillars
Aircraft Hangars – large beam spans for wingspan clearance
Retail and Trade Units – simple, quick builds with adaptable layouts
What to Consider When Choosing a Portal Frame
Purpose and Building Layout
Decide how the space is to be used. Do you need open plan space, separate rooms, or equipment fitted overhead? This affects span and layout.
Loads and Forces
Consider wind, snow, roof load, mezzanine floors, or any plant that may affect the load on the frame.
External Cladding and Insulation
Choose cladding based on thermal performance, appearance, and weather exposure. Insulated panels may be required for heated or chilled environments.
Planning Permissions
Portal frames will have to meet all national planning rules and building regulations. Visual amenity and environmental factors, especially in the countryside, will also be considered.
Ground Conditions
Type of soil and drainage will influence foundation design. Consult a structural engineer about an adequate base for your project.
How Steel Portal Frames Are Installed
Design and Fabrication
Structural engineers create technical drawings and fabricate the steel frame off-site.
Groundwork and Foundations
Site cleared, foundations established, and anchor bolts installed.
Frame Assembly
Columns and rafters are positioned using cranes and bolted or welded to each other.
Roof and Wall Cladding
Cladding panels are fitted to the frame. Doors, windows, and insulation are installed where necessary.
Finishing Work
Heating, lighting, and internal partitions, floors are fitted to specification.
Maintenance and Lifespan
Steel portal frames have minimal maintenance needs but need to be checked annually for signs of corrosion, loose bolts, or damaged joints. Painted or galvanised finishes help to coat the steel and can extend lifespan by many years.
A steel portal frame, when well maintained, could have a lifespan of 40–50 years or more.
Final Word
Steel portal frames are strong, adaptable, and quick to build — which makes them a reliable option for many types of projects. Whether you’re building a warehouse, a farm building, or a commercial unit, they offer practical advantages that can save time and money without compromising performance.
To achieve the best outcome, hire a competent structural engineer and seasoned contractor. They’ll assist in customizing the frame to your precise specifications and see to it that it meets all applicable standards from day one. Contact us to read their ultimate guide to steel portal frames.