The structural frame is the skeleton of any warehouse — it determines the building’s clear height, column spacing, and load-bearing capacity. For logistics operators, understanding the differences between steel frame and portal frame construction is essential for making informed decisions about their next facility.
Portal Frame: The Industry Standard
Portal frame construction is the most common structural system for single-storey industrial buildings in the UK. It consists of columns and rafters connected by rigid moment connections, forming a series of frames that span the width of the building. Portal frames are efficient, well-understood, and economical for spans up to approximately 50 metres. They are ideal for standard warehouse applications where clear spans of 25-40 metres are required, and where eaves heights do not exceed 12-15 metres.
The key advantages of portal frame construction include its cost-effectiveness for standard spans, the efficiency of material use (steel weight per square metre is typically lower than alternative frame types), the speed of erection, and the wide availability of specialist fabricators and erectors across the UK.
Multi-Bay Steel Frame: For Larger Facilities
For larger facilities requiring very wide clear spans (50 metres and above), very high eaves heights (15-18 metres or more), or multi-storey mezzanine structures within the building envelope, a multi-bay steel frame with lattice trusses or castellated beams may be more appropriate. These frames can achieve greater spans and heights than portal frames, accommodating the high-bay racking systems and automated storage and retrieval systems (AS/RS) that are increasingly common in modern logistics facilities.
Key Factors in Frame Selection
The choice between portal frame and steel frame construction depends on several project-specific factors: the required clear span (distance between columns), the required eaves height, the roof and imposed loading requirements, whether the building will accommodate cranes or heavy suspended equipment, the foundation conditions and their ability to resist the horizontal forces generated by portal frames, and the client’s requirements for future adaptability and extension.
FcMig’s Structural Expertise
At FcMig, we work with both portal frame and multi-bay steel frame systems, selecting the most appropriate structural solution for each project based on the client’s operational requirements, site conditions, and budget. Our team coordinates closely with structural engineers from the earliest design stages, ensuring that the frame design supports the building’s intended use while optimising material costs and construction programme. Recent projects include a 150,000 sq ft regional distribution centre with 15-metre clear heights and a 200,000 sq ft e-commerce fulfilment centre with a three-level mezzanine — both delivered using optimised steel frame designs.
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