Portal Frame
Portal frames are a type of rigid structural frame made from steel columns and rafters, joined with moment connections to form a stable, self-supporting structure. Known for their strength and ability to span wide distances without internal supports, portal frames are a go-to solution for large open areas. They’re quick to install, cost-effective, and suitable for both permanent and temporary structures.
What Is a Portal Frame? A Builder’s Guide to Structural Steel Solutions
When you’re building a shed, warehouse, or workshop, you need structure that’s efficient, durable, and fast to erect. A portal frame delivers all that. It’s a rigid structural system composed of vertical columns and horizontal rafters, joined with moment‑resistant connections for clear‑span buildings—no middle columns, just open space ready for work.
Understanding Portal Frames: The Backbone of Modern Builds
Portal frames account for around 50% of structural steel used in UK construction because they’re so efficient. These frames work by integrating columns and rafters into a single, continuous moment‑resistant structure that handles vertical, wind, snow, and even crane loads with ease. That design makes them ideal for commercial warehouses, workshops, industrial units, and large retail spaces.
Why Choose Steel Portal Frame? Strength, Speed, and Simplicity
Switching to a steel portal frame comes with proven benefits:
Speed of construction: Pre-fabricated steel frame systems reduce build time up to 50% compared to timber.
Material efficiency: Steel portals are economical—load capacity is high relative to material used.
Large, unobstructed spans: Typical portals span 20–60 m with no internal columns blocking space.
Durability and resistance: Steel stands up to pests, rot, and fire far better than wood.
Types of Portal Frames
Based on Structural Support and Span:
Single-Span Portal Frame
This simple frame—made of two columns and a rafter—provides a large clear span up to around 80 m, making it ideal for workshops, garages, and small factories.
Multi-Span Portal Frame
Multiple single-span sections are connected with intermediate columns to cover greater widths. Perfect for large warehouses or retail spaces with flexible layouts.
Portal Frame with Internal Mezzanine
Frames with integrated mezzanine floors add rigidity and provide extra usable space. A solid choice for offices or storage zones inside industrial sheds.
Tied Portal Frame
A horizontal tie connects the columns to support larger spans economically, enabling uninterrupted floor space. Often used in large factories or warehouses.
Based on Roof Shape:
Pitched Roof
Also called duo-pitch, this classic A-frame design slopes both ways and works well for spans up to 35 m. It’s the most common portal frame roof style.
Mono-Pitched Portal Frame
A single slope frame ideal for lean-to extensions, carports, or small sheds up to about 15 m span.
Curved Portal Frame
Curved members form the rafter—great for reducing wind uplift and adding aesthetic appeal. Ideal for hangars, auditoriums, or unique architectural buildings.
Mansard and Cellular Frames
Mansard frames allow higher central clearance with two different roof slopes. Cellular beams (with perforations) offer lightness and style but require ventilation considerations.
Steel vs Timber Portal Frame
Choosing between steel portal frame and timber portal frame depends on your build:
Span and strength – Steel offers longer spans (up to 60 m) and higher loads than timber.
Durability – Steel resists rot, insects, warping, and fire far better than timber.
Construction speed – Steel is quicker and more precise, with less on-site cutting. Timber takes longer and needs more labour.
Costs – While timber has lower initial costs, steel frames often provide better long-term value with easier maintenance and higher lifecycle strength.
Portal Frames as Part of the Structural Steel Framework
While portal frames are a cornerstone of many commercial and industrial buildings, they’re just one of several components that form a complete structural steel framework. Designed to span wide areas without the need for internal columns, portal frames provide the rigidity and shape needed for open, unobstructed spaces.
In most builds, portal frames work in tandem with structural steel beams to carry roof loads and with steel posts that anchor the system vertically. Together, these elements create a durable and efficient load-bearing structure.
Common Applications of Structure Steel Framework
Steel portal frames are everywhere:
Warehouses, distribution centres, factories, and workshops
Agricultural buildings like barns and equipment sheds
Commercial spaces such as showrooms, gyms, sports halls
Covered carparks, verandahs, and lean-tos that need durable roof structure
With portal frames, builders get clean spans and flexible internal layouts with minimal fuss.
Looking for Structural Steel Portal Frames Near You?
If you’re building in Melbourne or anywhere in Victoria, ISG Frames is your trusted local partner. We engineer, fabricate, and deliver steel portal frame systems that match your project specs, and we do it right here in Pakenham.
FAQs
How wide can portal frames span?
Steel portal frames typically achieve 20–60 m spans depending on frame type and design parameters.
Can you add multiple bays?
Yes. Multi-span portal frames connect additional frames side-by-side to create wide, open buildings.
Can I combine a portal frame with other structural steel frameworks?
Absolutely. Many builders integrate portal frames with secondary structural steel frameworks like mezzanine floors, roof trusses, or support posts. Our team can fabricate all components to ensure perfect alignment during install.
Related Solutions
Beams
Columns
End-to-end engineering and fabrication with certified quality like TRUECORE® steel
