Types of Structural Loads Explained

Every building has to carry structural loads — the forces and weights acting on it throughout its life. Some never change, like the weight of the building itself; others come and go, like people, furniture, wind and rain. Understanding the types of structural loads is the starting point for any design, because the whole frame exists to gather these forces and carry them safely down to the ground.

This article walks through the main categories of structural loads, explains how they differ, and describes how engineers combine them to make sure a structure is safe under every reasonable situation it might face.

Dead loads: the permanent weight

Dead loads are the permanent, fixed weights of the structure and everything built into it: the slabs, beams, columns, walls, screed, finishes, cladding and fixed services. They do not change once construction is complete, which makes them relatively predictable — an engineer can calculate them from the materials and dimensions on the drawings.

Dead load is usually the largest single load a building carries, because the structure itself is heavy, particularly in concrete buildings. Getting it right matters: underestimating finishes, screeds or future overlays is a common source of trouble, since these add permanent weight the original design may not have allowed for.

Live loads: the variable, occupancy loads

Live loads (also called imposed loads) are the movable, variable loads a building must support in use: people, furniture, equipment, stored goods and vehicles. They change with time and with how a space is used, so they cannot be pinned to an exact figure. Instead, codes specify design values for each type of occupancy — a residential floor, an office, a shopping area, a warehouse and a car park all have different live-load requirements.

Because live load depends on use, changing a building’s use can change its loading. Turning a light residential space into a heavy storage area, for example, may exceed what the floor was designed for. This is one reason changes of use often require structural review, and it links directly to the role of a structural engineer.

Wind loads: lateral pressure on the envelope

Wind acts horizontally, pushing and pulling on a building’s faces and roof. For low buildings the effect is modest, but for tall or slender structures, wind becomes one of the governing loads — it tries to push the building sideways and, in extreme cases, to overturn it. Wind also creates suction on roofs and the leeward face, which is why roof coverings and cladding fixings are designed against uplift.

Resisting wind requires a clear lateral load path: the envelope collects the pressure, transfers it into floors, and the floors deliver it into walls or bracing that carry it to the foundations. Facade elements have their own wind design too, which is part of facade engineering.

Other loads engineers consider

Beyond the three main categories, several other loads can matter depending on the project:

Seismic loads from earthquakes induce horizontal forces as the ground shakes the building. Singapore is in a region of low seismicity but can feel distant tremors, so far-field effects are considered for certain structures.
Water and earth pressure act on basements, retaining structures and tanks. These relate to retaining walls.
Thermal loads arise as materials expand and contract with temperature, which is why long structures need movement joints.
Construction loads occur temporarily during building, when wet concrete, stacked materials and equipment impose forces the finished structure may never see again.
Impact and dynamic loads from vehicles, machinery or crowds add effects beyond their static weight.

How loads combine

A structure rarely faces just one load at a time, so engineers do not simply add the worst of everything together. Instead, design codes define load combinations that pair loads realistically, applying factors that reflect how likely they are to occur together at their maximum. Full live load and peak wind are unlikely to coincide exactly, for example, so the combination factors account for that.

The structure is then checked against every relevant combination to find the most severe case for each member. A beam might be governed by gravity loads, while a column or wall is governed by a wind combination. This systematic checking is what gives confidence that the building is safe across its whole life, not just under one idealised condition.

Why this matters to building owners

The practical lesson is that a building is designed for a specific set of loads, and anything that increases them — heavier finishes, new equipment, a change of use, an extra storey, or storing dense materials — can erode the safety margin. None of these should be assumed harmless. If you are planning a change that adds weight or alters how a space is used, a quick structural check is worthwhile. Our structural engineering consultancy can advise on whether your structure can take it.

Frequently asked questions

What are the main types of structural loads?

The main types are dead loads, which are the permanent weight of the structure and finishes; live loads, which are variable occupancy loads like people and furniture; and lateral loads such as wind and, in some regions, seismic forces.

What is the difference between dead load and live load?

Dead load is the fixed, permanent weight of the building itself and its finishes, while live load is the changeable load from how the building is used, such as people, furniture, equipment and stored goods.

Why do engineers use load combinations?

Because a structure faces several loads that vary independently, engineers combine them with factors that reflect how likely they are to peak together, then check each member against the most severe realistic combination.

Does changing a building’s use affect its loads?

Yes, because live loads depend on occupancy; converting a light residential or office space into heavy storage or assembly use can exceed the floor’s designed capacity and usually requires structural review.

Is wind load important in Singapore?

Yes, particularly for tall, slender or exposed structures and for facades and roofs, where wind pressure and suction can govern the design even though Singapore is not in a high-wind storm belt.

Planning a change that adds weight or alters how a space is used? Talk to our consultancy or get in touch.