Steel buildings UK: types, spans, costs and what to ask before you buy

A steel building is any building whose structure is a steel frame, and in the UK that usually means a portal frame: columns and rafters joined rigidly at the eaves and ridge, with cladding fixed to purlins and rails. Beyond that, steel buildings differ by structural form, by use and by how they are procured, and each choice changes cost, programme and risk.

The main types of steel building

There are three useful ways to sort steel buildings. By structure, which is how the frame carries load. By use, which sets height, floor loading and fit-out. And by construction route, which is who designs, fabricates and builds it. Most confusion in quotes comes from comparing buildings that differ on one of these without saying so.

Steel building types by structure

The Steel Construction Institute (SCI) describes the portal frame as the usual form for single-storey industrial and commercial buildings, with several variants for specific problems. Our guide to portal frame buildings goes through how they work. These are the structural types you will meet.

• Clear-span portal frame. A single bay with no internal columns. Typical spans are 15 to 50 metres, and the most efficient symmetric pitched frames are 25 to 35 metres. Best for warehouses, workshops and farm buildings that need open floor.
• Multi-span portal frame. Two or more bays side by side. Leaving out the valley columns between bays lowers cost and gives larger column-free areas. Best for very wide buildings, where one huge span would be heavy.
• Mono-pitch portal. A single slope, usually up to about 15 metres in span. Best for narrow buildings or sites where a neighbouring building limits the roof shape.
• Tied, propped, mansard and crane portals. Variants that control eaves movement, reduce rafter size, increase mid-span height or carry crane rails for cranes up to about 20 tonnes.
• Trusses and space frames. Used where a roof has to span beyond the practical limit of a portal frame. Lattice trusses reach 50 to 80 metres and space frames about 100 metres, at a cost premium that rules them out for routine commercial and industrial spans.
• Multi-storey steel frame. A column-and-beam frame for buildings of two or more floors, used for offices, retail and mixed-use. Floors are composite metal decking or precast concrete.

Span, height and steel weight at a glance

Span and height set the weight of steel, and weight drives cost. The SCI gives clear heights to the underside of the haunch of 8 to 18 metres for portal frames, a roof pitch of 5 to 10 degrees, and frame spacing of 6 to 8 metres. Low-eaves frames of 4 to 8 metres weigh roughly 30 to 40 kg per m² of floor, while high-eaves frames of 10 to 13 metres weigh 40 to 50 kg per m², about 20% more. Northlight-type rooflights can add as much as 35% to the frame cost. Before you fix a height, ask what will be stored or built under the roof, because height you do not use is an expensive habit.

Steel building types by use

The use sets eaves height, floor loading, envelope and services, which is why a warehouse and a showroom with the same footprint cost different amounts. These are the uses we build for, with the points that matter in each.

• Agricultural buildings: livestock housing, machinery stores, grain and feed stores. Simple envelope, durable cladding and often open sides. Planning follows the agricultural rules, covered in our farm buildings guide and on our agriculture and equine page.
• Industrial and warehouse buildings: manufacturing, storage and distribution. Height, floor loading, doors and yard dominate. See industrial and warehousing and our guide to warehouse build costs.
• Commercial buildings: offices, showrooms and business units, often combining a steel shell with a more finished envelope and fit-out. See commercial and offices and the Claybrook showroom and office project.
• Retail and roadside: shops, food outlets and drive-throughs, where programme and appearance matter. See retail and roadside.
• Sport and leisure: climbing centres, studios, indoor arenas and halls, which need clear span and often unusual height. See sport and leisure.
• Storage and self storage: repeated bays and many doors, with the layout driven by the unit mix. See self storage and the Titan Self Storage project.
• Transport and motor trade: workshops, depots and showrooms with large doors and heavy floors. See transport and logistics.

Steel building types by construction route

This is the choice people overlook, and it changes who carries the risk.

• Kit or pre-engineered building. A standard frame range supplied with cladding, selected doors and delivery, usually erected by the buyer or a subcontractor. Groundworks and erection are excluded, so the headline rate sits below a comparable package price. Best for simple, low-risk buildings on a prepared base.
• Bespoke engineered steel building. A frame designed to the site, loads and use, fabricated to order. Best where the building has height, crane loads, a mezzanine or a difficult site.
• Design and build. One contractor takes design, fabrication, groundworks, erection and cladding under a single contract. It removes the gaps between suppliers, and our design and build service is organised this way.
• Modular steel building. Built in sections and assembled on site, mainly for repeatable accommodation and plant.

What steel buildings cost

A price for a steel building can mean the frame only, the weathertight shell, or a finished building with services. Establish which before comparing numbers. For a single-storey portal frame, the frame alone is £116 to £151 per m² with low eaves of 6 to 8 metres and £141 to £180 per m² with eaves of 10 to 13 metres, according to Costing Steelwork 37 (September 2026). Our guide price for a basic building package is £200 to £350 per m² excluding groundworks, and a shell with fit-out is around £350 to £600 per m². Beyond that, a fully serviced building is priced on its services and fit-out rather than its structure. The one fully costed example in the SCI's cost pages, a Stoke warehouse, came to £920 per m² with the frame at £127, about 14% of the total.

Multi-storey frames cost more per square metre because the steel is heavier and floors are added. The SCI's cost planning guidance gives, as at the third quarter of 2025, £158 to £191 per m² for a low-rise frame with short spans and a repetitive grid at 55 kg per m², and £266 to £299 per m² for a high-rise long-span frame at 90 kg per m². Composite floors add £90 to £140 per m², and hollowcore precast floors with topping £137 to £193 per m². Our full guide to steel frame building cost shows the layers, and steel prices and imports explains why quotes need a validity date.

Certification: UKCA or CE and Execution Class

All fabricated structural steelwork delivered to a site in Great Britain must be UKCA or CE marked against BS EN 1090-1, as the SCI's UKCA marking guidance states. BS EN 1090-2 covers execution. The Execution Class sets the level of control, and Execution Class 2 (EXC2) is appropriate for the majority of buildings in the UK. A fabricator with EXC3 capability can work on EXC1 to EXC3 projects, while one certified only to EXC2 is limited to EXC1 and EXC2.

Ask any supplier, kit or bespoke, for the certificate and the Execution Class it covers, and check the certificate number against the issuing body's register. The SCI notes that UKCA certification requires a UK Approved Body, which carries out the initial plant and factory production control inspections and annual audits and issues the certificate and welding certificate showing the Execution Class achieved.

Planning and building regulations for a steel building

A steel frame is a construction method, not a planning category. What counts is the use, size and location. An industrial or warehouse building falls under permitted development Class H only as an extension or alteration to an existing building, or a new building of up to 200 square metres within its curtilage, so a new commercial building of any scale needs planning permission. The limits are set out in Class H of Part 7. Farm buildings follow the agricultural rules in our agricultural planning guide, and garden and domestic outbuildings follow different permitted development limits again.

All new buildings need building control approval. For non-domestic buildings the energy requirements are in Approved Document L Volume 2, which we cover in Part L for commercial buildings.

Questions to ask any steel building supplier

• Is the frame designed for this site's wind and snow loads, and by whom?
• Who designs and builds the foundations and floor, and are they in the price?
• Does the price include cladding, insulation, doors, rainwater goods and erection?
• Who fabricates, who erects, and what certificates and Execution Class apply?
• What warranties come with the frame and the cladding?
• How long is the price valid, and what happens if steel prices move?
• What is the lead time from design approval, and what could change it?

Our guide to checking a contractor before you sign covers the wider checks.

How to choose the right type of steel building

Start with the use, then work outwards. If you need open floor up to 50 metres wide and one level, a clear-span portal frame is the default. If the width is greater, look at a multi-span frame. If you need two or more floors, a multi-storey frame or a portal with a mezzanine is the answer, and our guide to mezzanine floors explains the rules. If you need a roof span beyond about 50 metres, you are into trusses or space frames. Then choose the construction route by risk: a kit for a simple building on a prepared base, bespoke or design and build when the building has height, loads, a difficult site or a tight programme.

How MSB Group builds steel buildings

We design, fabricate and erect steel framed buildings as one package, so the frame, foundations and cladding are designed together. We fabricate in our own 45,000 sq ft workshop, erect with our own teams and manage the groundworks. Our steelwork carries UKCA marking and UKAS-accredited SCCS certification, and we are on Constructionline at Gold level. Read more on our steel framed buildings page, and see cladding and roofing and groundworks for the parts of the package.

Next step

Send us the use, the site, a rough footprint and any drawings through our contact page. We will tell you which structural type and construction route we would use, give you an indicative range and say what it includes.

Questions we get asked

What are the main types of steel building?

By structure: clear-span portal frames, multi-span portal frames, mono-pitch frames, truss and space frame buildings and multi-storey steel frames. By use: agricultural, industrial, commercial, retail, leisure and storage. By route: kit, bespoke engineered, design and build and modular.

How much does a steel building cost in the UK?

The frame alone is about £116 to £180 per m², depending on eaves height. A basic building package starts at around £200 to £350 per m² before groundworks, and a fitted building can pass £600 per m².

What is the maximum span of a steel building?

Portal frames typically span 15 to 50 metres, with 25 to 35 metres the most efficient. Trusses reach 50 to 80 metres and space frames about 100 metres, but at a cost premium that rarely makes sense below 50 metres.

How long does a steel building last?

A properly protected steel frame is designed for decades of use, and the life of the building is set mostly by the cladding, roof and maintenance. The design life should be stated in the specification.

Do steel buildings need planning permission?

Usually, for commercial and agricultural buildings, though limited extensions to an existing industrial building or warehouse can be permitted development. Check with your local planning authority.

Is a steel building cheaper than other types of construction?

For large-span single-storey buildings the SCI calls the portal frame a highly cost-effective solution and the most economical up to about 50 metres. For other building types, compare quotes on the same specification.

What certification should a steel building have?

The steelwork must be UKCA or CE marked to BS EN 1090-1 for sites in Great Britain, with the Execution Class stated. EXC2 suits most buildings.