What is needed to make a structural calculation?

Structural analysis is the technical process that enables the design and verification of a building to ensure it is safe, stable and fit for its intended use. It is not merely a matter of estimating materials: it involves analysing loads, studying the ground conditions, selecting construction systems, modelling the behaviour of the structure and demonstrating compliance with the relevant regulations.

A well-designed structural system ensures that a dwelling, public building, commercial premises or refurbishment project can adequately withstand its own weight, day-to-day use, wind loads, potential seismic activity and other stresses that may arise during its service life. Furthermore, sound structural analysis prevents over-design, optimises the use of materials and improves the project’s economic and construction efficiency.

At Velló Monfort Arquitectes, we carry out structural calculations for new-builds, refurbishments, renovations, extensions and residential or public projects, incorporating safety, regulatory compliance, architectural design and constructability from the very earliest stages.

What is structural analysis and why is it important?

Structural analysis determines how a building’s structure should be constructed in order to correctly transfer loads to the ground. To this end, elements such as foundations, columns, walls, beams, floor structures, slabs, staircases, roofs and any necessary reinforcements are analysed.

Its importance is twofold. On the one hand, it ensures the structural safety of the building. On the other, it enables the design to be optimised to avoid solutions that are unnecessarily costly or difficult to implement. A well-planned structure must be safe, durable, consistent with the architectural design and within budget.

In a new-build project, structural calculations are carried out in close coordination with the architectural design from the outset. The layout, the spans between supports, the cantilevers, the position of openings and the geometry of the building all have a direct influence on the structural solution.

1. Background information on the architectural project

Before carrying out structural calculations, it is necessary to be familiar with the architectural design. The calculations cannot be carried out in isolation, as the structure must be tailored to the design, the intended use and the actual requirements of the building.

The most important background information is as follows:

• type of building: detached house, block of flats, commercial premises, public facility or refurbishment;
• number of plants;
• interior layout;
• lights between supports;
• position of staircases and stairwells;
• roof geometry;
• the presence of basements, terraces, overhangs or swimming pools;
• intended use of each space;
• aesthetic and structural considerations;
• approximate construction budget.

In a detached house, for example, the structure must be adapted to the way the house is lived in, its relationship with the garden, its orientation, the views and the integration of indoor and outdoor spaces.

2. Geotechnical survey and site characteristics

The ground conditions are one of the most important factors in any structural calculation. The foundations must safely transfer the building’s loads to the ground, preventing excessive settlement, cracks, deformation or structural defects.

To do this, you need to know:

• bearing capacity of the ground;
• soil type;
• depth of resistant strata;
• presence of water;
• the difficulty of the terrain;
• slope of the plot;
• risk of expansion or backfilling;
• seismic conditions in the area.

In new-build projects, a geotechnical survey is usually essential for determining the type of foundation required: strip footings, slabs, piles, retaining walls or other solutions. In renovation or extension projects, it may also be necessary to assess the existing foundations before adding new loads or altering the structure.

3. Structural load analysis

Load analysis is one of the first stages in structural design. Every building is subject to loads which must be correctly identified, quantified and combined to ensure its stability.

The current entry already distinguishes between permanent, variable and accidental loads, including the structure’s dead weight, building use, wind, snow and seismic actions.

Permanent, variable and accidental loads

Permanent loads are those that act continuously: the structure’s own weight, external walls, roofs, floor slabs, internal partitions, cladding and fixed installations.

Variable loads depend on the intended use: people, furniture, storage, equipment, vehicles, maintenance, wind or snow, as applicable.

Accidental loads are less frequent but safety-critical events, such as earthquakes, impacts, fires or other exceptional situations.

A reliable structural analysis must take into account not only each load individually, but also their combinations. The structure must perform correctly under various scenarios throughout its service life.

4. Applicable regulations: Structural Code and CTE

In Spain, structural design must comply with current technical regulations. The Structural Code, approved by Royal Decree 470/2021, sets out requirements relating to design principles, structural analysis, materials, durability, construction, quality control and maintenance of concrete, steel and composite structures. The Official State Gazette (BOE) itself explains that structures are fundamental to the safety of buildings and their users.

Furthermore, the project must comply with the Technical Building Code, particularly with regard to requirements concerning structural safety, fire safety, safety in use, habitability and energy efficiency.

Within the text, you can link to the BOE naturally as follows:

The Structural Code published in the Official State Gazette (BOE) is the basic regulatory framework for the design and construction of concrete, steel and composite structures in Spain.

5. Selection of structural materials

The choice of materials determines the strength, durability, cost, speed of construction, maintenance and environmental impact of the structure. There is no single material that is universally superior; the decision depends on the type of building, the span lengths, the site, the budget, the regulations and the architectural expression sought.

Concrete, steel, timber and composite systems

Reinforced concrete is very commonly used in construction due to its strength, durability and good compressive performance. It is used in foundations, columns, walls, slabs and floor structures.

Structural steel allows for large spans, lighter structures and solutions with high load-bearing capacity. It is commonly used in industrial buildings, extensions, reinforcements or structures where speed of assembly is a priority.

Structural timber can be an attractive option for sustainable projects or homes where lightness, warmth and a lower environmental impact are sought, provided that its strength, protection and durability are adequately justified.

Composite structures combine materials, such as concrete and steel, to make the most of the advantages of each. The Structural Code expressly includes composite concrete and steel structures within its regulations.

6. Modelling, calculation and structural verification

Once the data, loads, site conditions and materials have been defined, the structural modelling is carried out. Specialised tools are used for this purpose, which enable the behaviour of beams, columns, floor structures, slabs, walls and foundations to be simulated.

Modelling helps to check:

• deformations;
• tensions;
• global stability;
• efforts in each element;
• arrows;
• vibrations, where applicable;
• safety against vertical and horizontal loads;
• seismic behaviour;
• dimensioning of reinforcement, sections or profiles.

This post mentions specialist software such as SAP2000, ETABS and CYPECAD for creating three-dimensional models and analysing how loads affect structural elements.

Software is no substitute for technical judgement. A sound structural analysis requires interpreting results, identifying inconsistencies, refining solutions and coordinating the model with the architectural design and the actual construction of the building.

7. Design of foundations, columns, beams, floor structures and slabs

Following the analysis, the main structural elements are dimensioned. Each one fulfils a specific function within the building.

Foundations transfer loads to the ground. They can be shallow, such as strip footings or slabs, or deep, such as piles, depending on the geotechnical conditions.

The columns bear vertical loads and transfer them to the foundations. Their positioning must be coordinated with the architectural layout to avoid interfering with living spaces, car parks, commercial premises or circulation routes.

Beams enable spans to be spanned and transfer loads from floor slabs or roofs to columns or walls.

Floor slabs and beams form the horizontal planes of the building and must meet requirements in terms of strength, deflection, acoustics, services and compatibility with the finishes.

In projects featuring terraces, swimming pools, large windows or cantilevers, the calculations must be carried out with particular care to avoid deformation, cracks or inefficient solutions.

8. Structural calculations for refurbishments and renovations

Structural analysis is not limited to new-build projects. In a renovation or refurbishment, it may be essential when removing partition walls, creating openings, replacing floor slabs, reinforcing beams, adding a storey, changing the use of the property or identifying structural defects.

In a comprehensive housing renovation, a structural analysis helps to determine which elements can be altered, which must be retained, and what reinforcements are required to carry out the work safely.

It is also important in housing renovation projects, particularly when the work involves load-bearing walls, columns, floor slabs, roofs or foundations.

In existing buildings, before carrying out any calculations, it is advisable to analyse:

• original structure;
• plans available;
• condition;
• cracks or deformations;
• damp;
• previous interventions;
• changes in use;
• existing materials;
• compatibility between the old and new structures.

9. Documentation required for a structural analysis

To carry out a rigorous structural analysis, the engineer needs to gather sufficient documentation. The more clearly defined the initial information is, the more reliable the result will be.

The usual documentation includes:

• architectural plans;
• assessment of the current situation, if it is a refurbishment;
• geotechnical survey;
• building usage data;
• applicable town planning and technical regulations;
• planned materials;
• information on heavy machinery;
• details of roofs, terraces or swimming pools;
• photographs and inspection visits;
• plans of the existing structure, if available;
• the developer’s or owner’s objectives;
• budget and planned construction method.

The results must be incorporated into the technical design by means of structural drawings, a calculation report, measurements, construction details and specifications for the works.

Frequently asked questions about structural analysis

What is needed to make a structural calculation?

It is necessary to be familiar with the architectural design, the building’s intended use, the anticipated loads, the geotechnical survey, the applicable regulations, the structural materials, the building’s geometry and the construction conditions. In the case of refurbishments, the existing structure must also be analysed.

Who can carry out a structural analysis?

Structural calculations must be carried out by a competent engineer with professional training and responsibility in the field of structural engineering. In building construction, this is usually part of the technical project drawn up and coordinated by architects and specialist engineers.

Is a geotechnical survey compulsory?

In new-build projects, this is usually necessary to design the foundations correctly. Without soil data, the foundation design may be unreliable or inaccurate. In renovation or extension projects, it may be advisable if additional loads are introduced or work is carried out on the foundations.

When do I need structural calculations for a renovation?

You need this when the renovation affects structural elements, such as load-bearing walls, columns, beams, floor slabs, roofs, foundations, the creation of openings or extensions. It is also required when the use of a building is changed or the anticipated loads are increased.

Which regulations govern structural calculations in Spain?

In Spain, the Structural Code, the Technical Building Code and the specific regulations applicable depending on the type of building, materials, use, location and scope of the project must be taken into account.

Can a good structural analysis save money?

Yes. A well-executed structural analysis prevents over-dimensioning, reduces material wastage, improves the quality of the build and minimises the risk of defects or alterations during construction.

Structural analysis with Velló Monfort Arquitectes

A sound structural analysis begins long before beams or columns are dimensioned. It requires understanding the project, surveying the site, analysing loads, applying regulations, selecting suitable materials and coordinating the structure with the architecture.

At Velló Monfort Arquitectes, we carry out structural calculations for residential properties, refurbishments, renovations, extensions and public buildings in the Valencian Community. If you need to assess the structural feasibility of a new-build project or a refurbishment, you can contact our architectural practice in Gandía or request an initial consultation via the Velló Monfort Arquitectes contact page.