Most of a skyscraper's load is its own weight: the dead load (the structure) is larger than the live load (people, furniture, vehicles). So the lower levels need much more structural material than the upper ones.

Wind pressure increases with height. For very tall buildings the wind loads are larger than the dead or live loads, and the sideways wind load on supertall structures is generally the governing factor in structural design. Some structural engineers define a high-rise as any vertical construction where wind is a more significant load than earthquake or weight. Engineers study wind forces on tall buildings so they can build with a minimum of material and still be safe in very high winds.

By 1895 steel had replaced cast iron as the structural material of skyscrapers. It could be formed into many shapes and riveted, which made strong connections. Steel-frame construction overtook brick and mortar from the end of the 19th century, and in the 20th century it and reinforced concrete took over as steel got cheaper and labor got more expensive.

The tube system treats a tall building as a hollow cylinder standing on the ground like a cantilever, so that the whole building resists lateral loads (wind, earthquake, impact). Fazlur Rahman Khan introduced the system while working at Skidmore, Owings & Merrill in Chicago. In the simplest tube, closely spaced columns around the outside are tied together by deep beams with rigid connections. Together they form a dense, strong structural wall around the building's perimeter.

In a tube building the exterior frame is made strong enough to resist all the sideways loads, so the inside only has to be framed to carry gravity loads. A hull-and-core tower has an inner core tube for elevators and services plus an outer tube, and the outer tube usually takes most of the gravity and sideways loads because it is stronger. The tube system can be built in steel, concrete or a composite of both. Most buildings over 40 stories built since the 1960s use this type of structure.

Since about 1960 tubular designs have let towers use less material and still go higher. Willis Tower uses a third less steel than the Empire State Building, and the design leaves fewer interior columns and more usable floor space.

Elevators shape a skyscraper's design: a taller building needs more elevators, but the shafts use up valuable floor space, and a service core that grows too big cuts the building's profit. Some towers use sky lobbies: express elevators carry people to upper floors that act as bases for local elevators, so shafts can be stacked on top of each other to save space.

Most skyscrapers have a steel frame and shear walls that hold up curtain walls. The curtain walls either rest on the frame below or hang from the frame above, instead of being load-bearing walls.

Engineers choose deep foundations for skyscrapers because of very large design loads, poor soil near the surface, or site limits such as property lines. When one pile cannot carry the load, groups of piles are connected by a pile cap, a large concrete block holding the pile heads, which spreads the load among them. A pneumatic caisson is a bottomless box, sealed at the top and filled with compressed air to keep water and mud out at depth. An airlock gives access to the chamber. A caisson is lowered through soft mud until it reaches suitable foundation material. Bedrock is preferred, but a stable, hard mud is sometimes used when bedrock is too deep.

A tuned mass damper is a mass on damped springs mounted in a structure. Its oscillation frequency is tuned to match the structure's resonant frequency, and it reduces the structure's maximum motion while weighing much less than the structure. Taipei 101 has a huge pendulum at the top that weighs 660 tonnes (as of November 2026). It swings the opposite way from the tower, which helps cancel out its swaying. During Typhoon Soudelor in August 2015, its damper swung 1 meter, and a bumper ring limits its swing to 1.5 meters.

Base isolation is a set of structural elements that largely decouples a building from the shaking ground beneath it, so earthquake motion is not passed fully to the structure above. One kind uses linear-motion bearings that let the building move, oil dampers that absorb the forces of the movement, and laminated rubber bearings that return the building to its original position after the earthquake.

The Citicorp Center in New York was a 59-story tower, completed in 1977. A church stayed on one corner of the site, so the tower floated above that corner. To lift it, LeMessurier put the support columns at the middle of each side instead of at the corners. A light steel frame made it so efficient that it was light and more likely to sway in wind, and a tuned mass damper sat at its top.

In 1978 a student phoned the engineer LeMessurier, a year after the tower was finished. The student said the wind checks covered winds blowing straight at the faces but not quartering winds that hit the corners. LeMessurier found that the braces' connections had been bolted instead of welded as designed, a change made during construction.

With the corrected figures, LeMessurier estimated about a 1 in 16 chance of failure under the right quartering wind conditions. The fix was to weld steel plates over the bolted joints. Welders worked at night while the building was in use. The repair was a race against the hurricane season, and the engineer, the architects and Citicorp fixed the issue as a hurricane threatened.

Words to know

• cantilever: fixed-end beam
• caisson: sealed digging box
• decouples: separates
• resonant: naturally swaying