Steel structures in architecture: pros, cons and examples

Without steel there would be no skyscrapers, long-span bridges or vast column-free halls. Metal transformed architecture in the 19th and 20th centuries and continues to do so – today not only in big cities but also in family homes, industrial buildings and interiors.

This article explains when a metal structure is a good choice, what its strengths and weaknesses are, and what it looks like in buildings everyone will recognise.

What is a metal structure?

A metal structure is the load-bearing system of a building or structure made of metal elements – columns, beams, trusses and bracing, joined with bolts or welds. In construction this almost always means steel; aluminium is more often used for facades and window frames.

The elements are fabricated in a workshop to precise drawings and assembled on site. This makes steel construction closer to assembly than to traditional “wet” construction with concrete and brick. The precision of factory fabrication, however, demands an equally precise design – a mistake in the drawings is hard to put right on site.

What are the advantages of metal structures?

The main advantage is high strength combined with low self-weight. The others follow from it.

• Large spans. Steel makes halls, industrial buildings and roofs without intermediate columns possible.
• Fast assembly. Factory-made elements go together quickly and are barely affected by the season.
• Lighter foundations. A lighter structure places less load on the ground.
• Earthquake performance. Steel is a ductile material – it deforms before it fails, which matters in seismic regions such as Bulgaria.
• Flexibility. The structure can be extended, altered and even dismantled.
• Recycling. Steel can be remelted many times without losing its properties.
• Expressiveness. Exposed steel is an aesthetic in its own right – from industrial style to high-tech architecture.

What are the drawbacks and how are they solved?

Metal structures have three main weaknesses – corrosion, behaviour in fire and thermal conductivity – and all of them are dealt with at the design stage.

• Corrosion – steel is protected by hot-dip galvanising, anti-corrosion paints or a combination of the two. Details must be designed so that they do not trap water.
• Fire – at high temperatures steel loses its load-bearing capacity. Intumescent paints, plasterboard linings or concrete encasement are therefore used, as required.
• Thermal bridges – metal conducts heat very well. Where the structure passes through the insulation, for example at cantilevered balconies or columns at the facade, special thermal breaks and careful detailing are needed to avoid heat loss and condensation.
• Sound – lightweight metal floors and walls transmit noise more easily; this is solved with suitable floor and wall systems.

Steel or concrete: which should you choose?

The choice depends on the type of building. The two materials often work together – reinforced concrete is the best example.

• Steel is better suited to halls, industrial buildings, large roofs, additional storeys on older buildings, fast-track construction and bold architectural forms.
• Reinforced concrete is better suited to the typical multi-storey residential buildings found in Bulgaria, basements and buildings where mass helps with sound insulation and thermal stability.
• A combination – a concrete core with steel floors, or a steel extension on top of a concrete building – offers the advantages of both materials.

Where are metal structures used?

From record-breaking skyscrapers to the staircase in your living room, here are the most typical applications.

Skyscrapers

The Empire State Building in New York was built with a steel frame in the early 1930s. The Willis Tower in Chicago uses a system of bundled steel tubes that makes its enormous height possible.

Bridges and infrastructure

San Francisco’s Golden Gate suspension bridge is a symbol of steel engineering. The Eiffel Tower in Paris, built of wrought iron for the 1889 World’s Fair, shows how expressive a metal structure can be.

Sports and cultural buildings

The Olympic Stadium in London, built for the 2012 Games, uses a steel structure that allowed rapid assembly. Frank Gehry’s Guggenheim Museum in Bilbao is clad in titanium sheets over a complex steel frame – without the metal structure these forms would have been very hard to achieve.

Houses and additional storeys

Lightweight structures made of cold-formed steel sections are also used for family homes, and steel frames for extensions and conversions where heavy construction is not possible. Adding a storey to an old building with a lightweight steel structure is often the only way to gain a floor without overloading the existing walls and foundations – following a survey and a structural engineer’s assessment, of course.

Industrial buildings, warehouses and production facilities

Here a metal structure is practically the standard. Frames of steel columns and beams or trusses cover large areas without intermediate supports, and sandwich-panel cladding means the building can be completed in a short time. Good architectural design can turn even such a utilitarian building into a memorable one, with attention to proportions, colour and entrances.

Interiors

Metal staircases, balustrades, mezzanines, frames for glass partitions and furniture. Black steel is an iconic part of industrial style, and stainless steel of minimalist kitchens. Slender metal sections allow staircases that seem to float in mid-air and glass walls with almost invisible frames – solutions that would look far more massive in timber or concrete.

How is a building with a metal structure designed?

1. Architectural concept – the form, the openings and what will remain exposed are defined.
2. Structural scheme – the structural engineer selects the system of columns, beams and bracing and sizes the elements.
3. Details and protection – corrosion and fire protection, thermal bridges and the connection to the facade are resolved.
4. Construction and shop drawings – each element is fabricated from these to millimetre precision.
5. Fabrication and assembly – the structure is erected on site, followed by the roof, facade and finishing works.

How we approach it at DARCH Projects

In our architectural design work we collaborate with structural engineers to use a metal structure where it gives a real advantage – large areas of glazing, cantilevers, additional storeys or exposed interior details. You can see what such solutions look like in our portfolio.

Frequently asked questions

Is a steel structure a good idea for a house?

It can be, especially if you want fast construction, large areas of glazing, cantilevers or a lightweight building on weaker ground. The design must address corrosion and fire protection, thermal bridges and sound insulation. For a typical two-storey house in Bulgaria, reinforced concrete and brick remain more common, so compare the options with an architect and a structural engineer.

How is steel protected from rust?

The most durable protection is hot-dip galvanising, in which the steel is coated with zinc. Systems of anti-corrosion primers and paints are also used, and the two are often combined. The detailing is just as important: elements should not trap water and should be well ventilated. Regular inspection of the paintwork extends the life of the structure.

Do steel structures perform well in a fire?

Steel does not burn, but at high temperatures it loses its load-bearing capacity. In buildings it is therefore protected with intumescent paints that swell when heated, with plasterboard linings or with concrete. The level of protection needed is set in the design according to the type and use of the building and the fire safety requirements.

Which is better: steel or reinforced concrete?

There is no universal answer. Steel is lighter, quicker to erect and better for large spans, halls and additional storeys. Reinforced concrete is more massive, better for sound insulation and the standard for most residential buildings in Bulgaria. Many buildings combine the two materials to make use of the advantages of both.