Phases of a Construction Project

Building construction involves a significant investment and a process that can take months or even years. During this time, various stages of the construction project unfold, their duration and success depending on the contractor’s management, the construction system employed, and the established timelines.

To understand the phases of a construction project, it is necessary to delve into each one in detail to unravel its complexity and grasp the associated risks. This approach allows us to evaluate the best execution option for a project, considering safety, cost control, and construction deadlines.

PHASES PRIOR TO BUILDING CONSTRUCTION

Before reaching the construction phase, we go through different stages that allow us to obtain a detailed architectural project, approved by the College of Architects, and with a building permit suitable for commencing construction.

PHASES OF AN ARCHITECTURAL PROJECT

The construction of a building constitutes one of the fundamental stages in an architectural project. It all begins with evaluating the project’s viability, moving through the definition of the complete project, to finally applying for a building permit and ultimately carrying out the execution of the building’s construction.

Let’s examine each of them in detail:

Project Feasibility Study

When undertaking a construction project, as with any other project, a preliminary study is necessary to evaluate the total investment and its amortization. This analysis is especially common in office building projects or residential developments. In the case of single-family home construction, viability can be assessed by comparing it with the acquisition of a second-hand home or by calculating mortgage amortization in relation to monthly rental investment.

Preliminary Project

The preliminary project is the essential starting point for construction development. It constitutes a creative phase where the environment is studied, and initial proposals are put forward through plans and models, which may be modified in later stages of the project.

The Basic Project

The basic project delves deeper than the preliminary project, defining the general characteristics of the work with greater precision by justifying specific solutions. This allows for a general conception of the building and the acquisition of the building permit.

The Executive Project

The executive project goes into greater detail and includes all the necessary documentation for the project’s construction. It is a detailed description covering all aspects of the building development: foundations, structure, and installations, all calculated and designed in compliance with current regulations, making precision crucial.

Endorsement and Building Permit Management

To initiate the building permit application process, both the basic project and the executive project must obtain the endorsement certificate from the College of Architects. Once the building permit is obtained, site management and its respective monitoring proceed to ensure correct execution.

Site Management

In this stage, the project is built in phases following the documentation presented. The role of the site manager will be necessary, who usually coincides with the architect responsible for the project’s design.

Site management, also known as facultative management, is the team of professionals responsible for supervising and ensuring the correct execution of the work. In Spain, according to the Building Planning Law (Ley de Ordenación de la Edificación), facultative management comprises the site manager (DO), the construction execution manager (DEO), and the health and safety coordinator (CSS).

The role of site manager can be performed by an architect or a technical architect, depending on who drafted the project. Both the site manager and the construction execution manager are responsible for ensuring proper project execution. However, their roles differ in their approaches: the site manager handles aesthetic, technical, urban planning, and environmental development, while the execution manager focuses on quality and quantity control. Thus, the DEO reviews the executive project, from foundations to finishes, and together with the architect, carries out the necessary setting-out in each phase of the work.

The Building Planning Law (LOE) includes specific rules that determine the responsibilities of these professionals. Accordingly, the risks that each agent assumes based on their activity are determined, as damages to the building or to third parties may arise during the construction process and must be covered by insurance.

Among the available insurances, the all-risk construction insurance stands out, covering all material damages to the building caused by accidental and unforeseen events. Likewise, it is important to have ten-year liability insurance, advance payment guarantee insurance, and civil liability insurance. [1]

AGENTS INVOLVED IN THE BUILDING CONSTRUCTION PHASE

Throughout the design process, several agents are involved in addition to the architect, due to the great complexity it entails. First, the developer is the one who commissions the project and provides all preliminary information to the architect, who will be primarily responsible for designing a building suitable for the client’s needs.

Subsequently, in the executive project stage, the role of the technical architect becomes relevant, as they will direct the ongoing construction work. Likewise, other specialized professionals participate, such as energy efficiency engineers, installation engineers, structural engineers, geologists, and surveyors, each contributing their expertise in the different phases of construction. Similarly, the construction company plays a fundamental role in undertaking the building’s construction.

In large-scale projects, it is vital to have a Project Manager, an individual who directs, coordinates, and manages the project from start to finish, ensuring efficient and orderly execution.

To carry out this process, it is essential to comply with the regulatory framework established by the Building Planning Law (LOE), which defines the basic requirements for building related to functionality, accessibility, safety, and habitability of buildings. [2] These requirements are developed in depth in the Technical Building Code (CTE). In addition to complying with these regulations, it is essential to obtain the endorsement from the College of Architects to carry out the project. [3]

PHASES OF THE CONSTRUCTION PROCESS

The construction process is divided into ten phases that are generally followed in any construction, although they may vary in complexity depending on the type of building or situation, and are as follows:

During each of these phases, work proceeds according to the documentation provided in the executive project and in accordance with the criteria, systems, and materials specified therein.

PHASE 1. SITE PREPARATION

Before constructing a building, it must be verified that the land in question is suitable and possesses the necessary properties for its occupation. This requires carrying out various preliminary studies conducted by geologists and surveyors.

The terrain has a significant impact on the building, as there are different types of soil, such as rocky, granular, cohesive, and deficient soils, which influence the foundation and structure of the project. It is essential that the project design adapts and conforms to the type of soil to ensure its proper functioning and durability.

GEOTECHNICAL AND TOPOGRAPHICAL STUDY

To determine the type of terrain and optimize construction, two fundamental studies are carried out: geotechnical and topographical.

The geotechnical study collects quantified information on the characteristics of the terrain, allowing for its recognition and classification. This information, along with data provided by the architect about the building, allows for a more appropriate resizing or replanning of the projected foundations and retaining walls. [5]

For this purpose, a reconnaissance campaign is carried out at various points on the plot, varying the depth according to the planned foundation in the project. Field tests are conducted, and samples are extracted for subsequent laboratory testing.

On the other hand, the topographical study precisely defines certain terrain characteristics such as elevation and levels through plans and graphic representations of the land. This topographical survey is accompanied by measurements of distances, elevations, or directions that allow the project to be located and construction errors to be avoided.

The information gathered through the geotechnical study and topographical profiles provides the necessary terrain values to adapt the project to the site and includes a report on recommended foundations. It also offers other complementary construction recommendations and work indications.

Both studies are carried out before the start of the technical project, but it is necessary to have them available when starting the work to share and evaluate the best execution solution. The steps followed in this first phase are the clearing of the area where the construction will be located and the leveling of the ground.

CLEARING AND BRUSH REMOVAL

Site clearing aims to remove any undesirable material or elements from the designated work area.

To do this, first, any debris or remnants of previous constructions, as well as the vegetation layer formed by weeds or shrubs, must be removed. In some cases, tree felling and root extraction will even be necessary. However, whenever possible, it is preferable to select trees that can be saved or relocated on the site.

Currently, there is a growing trend towards projects that respect the natural environment, opting for constructions that rest on few points, preserving existing trees or replanting them in different locations. Regenerative architecture, integrated into the landscape, seeks to minimize impact on the land and the natural environment, demonstrating a commitment to biosphere preservation.

LEVELING

Establishing the construction level is a crucial task that must be performed at the beginning of the project to set the ground floor level. To avoid potential flooding problems on the ground floor or the appearance of dampness in the walls, the marked level must be above the ground level. Additionally, if the plot is adjacent to the street, the ground floor level must also be situated above the sidewalk level.

From the ground floor level, which is taken as elevation 0.00, the other construction levels will be determined, and a setting-out approved by the Site Management will be carried out. This step is essential to ensure the correct execution of the project and prevent future problems related to the building’s elevation relative to the surrounding terrain.

PHASE 2. EARTHWORKS

This phase covers all activities related to earth movement, including excavations and backfills, material loading, transport, unloading, distribution, and compaction of earth. In small-scale projects, excavation can be done manually with shovels, which implies a lower environmental impact by avoiding the use of heavy machinery.

However, in most cases, due to the magnitude and complexity of projects, heavy machinery such as backhoes, hydraulic excavators, tractors, front loaders, rollers, or motor graders is used.

The characteristics of the excavation depend on the type of project, the terrain, and the planned foundations. The preliminary geotechnical study allows for estimating the magnitude and complexity of the excavation by providing information about the terrain.

There are two main types of excavations: for leveling and for foundations. Leveling excavations aim to standardize and level the starting ground for the building and include earth movements such as cut, excavation, and embankment.

On the other hand, this phase can generate a lot of waste and a significant impact due to earth movement. However, it is possible to reuse the excavated earth on the same site to minimize waste.

– Foundation Excavations

Foundation excavations are carried out using trenches, which are linear excavations where the foundation will later be placed. To perform these excavations, the earth is loosened and extracted following the marked guides that define the shape and dimensions of the trench needed for the planned foundation. These two steps are repeated until firm ground is reached, which will prevent unwanted settlements.

It is crucial that the bottom of the excavation is clean and level to ensure a solid base for the foundation. For this purpose, a lean concrete or fill is immediately poured after excavation, with a thickness of at least 10 cm. This helps maintain adequate ground conditions and provides a suitable base for the building’s foundation. [5]

PHASE 3. FOUNDATIONS AND EARTH RETENTION

The foundation is the structural element responsible for transmitting the total loads of the construction to the ground. Its function is to balance the rigidity of the building with the deformability of the terrain.

The choice of foundation type depends on factors such as terrain characteristics and the magnitude of the building. Regarding the soil, deformability, heterogeneity, the depth of the resistant stratum, seismicity, and moisture variations are taken into account. Regarding the building, the value of the loads transmitted to the soil, the allowable settlements, and its slenderness are considered.

Depending on the level of the resistant soil suitable for founding, foundations are classified as shallow, deep, or intermediate.

SHALLOW FOUNDATIONS

Shallow foundations, also known as direct foundations, are characterized by having the soil level suitable for founding close to the bottom of the structure. A foundation is considered shallow when the depth at which the footings are located is less than 3 meters. Although firm ground may be near the surface, it is advisable to go 0.5 to 0.8 meters below grade to ensure that the pressure it admits corresponds to the required foundation type. [6]

Usually, lightweight buildings or those with few floors are founded this way. However, within shallow foundations, there are different types that adapt to the specific requirements of each soil and the building’s loads.

– Footings

Footings are a type of shallow foundation used to support isolated elements of a structure, especially in home construction due to their economy and ease of execution.

There are three main types of footings according to their way of working: isolated, combined, and continuous. Isolated footings are those designed to support a single load element, such as pillars. They are an economical option when founding on rock or soils with allowable pressures greater than 0.15 N/mm2. [7]

These footings usually have a quadrangular shape, although in buildings with different spans in perpendicular directions, they can be rectangular. Their function is to support isolated, interior, party wall, or corner pillars.

The material used par excellence for foundations is mass concrete (HM) or reinforced concrete (HA). According to the EHE-08 structural standard, footings are classified as flexible or rigid. [8] Flexible footings have an overhang in the main direction greater than the depth of the footing, while rigid ones have an overhang less than twice the depth, allowing for better stress distribution. [9]

In order to provide rigidity to the whole and redistribute loads and pressures on the ground, isolated footings must be braced. This means they must be joined by tie beams or centering beams.

As for combined footings, these provide support for two or more pillars, while continuous footings support alignments of 3 or more pillars or even walls. These types of footings are used when pillars are very close to each other or when facing high loads that generate very close or overlapping isolated footings. The use of combined and continuous footings allows for uniform settlement between pillars and facilitates construction.

In the specific case of the continuous footing under a wall, it is generally built with reinforced concrete, but it can also be made of masonry, a more sustainable material.

– Foundation beams

Foundation beams are similar to continuous footings under walls. When the allowable pressure of the ground is low, a foundation using beams in two directions can be chosen, forming a grid foundation. In this case, all pillars rest on a single beam structure that contributes to the rigidity of the whole and avoids differential settlement.

– Foundation slab

Foundation slabs are characterized by covering the entire area of the building and providing support to all structural elements. They are used when the surface area of the footings exceeds 50% of the construction area or when the ground has a low bearing capacity, i.e., an allowable pressure between 0.08 and 0.15 N/mm2.

There are different types of foundation slabs, which are: continuous and uniform, with reinforcements under pillars, with pedestals, with a box section, ribbed, and lightweight.

These solutions help reduce stresses in the soil and minimize differential settlements. However, it is important to keep in mind that foundation slabs should not be used if the building is between party walls or if the soil is heterogeneous, as this could cause the slab and the entire building to rotate.

INTERMEDIATE FOUNDATIONS

Intermediate foundations, also known as semi-deep foundations, occur when the depth at which the contact between the foundations and the ground is located is between four and eight times the contact base (4B < D ≤ 8B). Within semi-deep foundations, we find foundation shafts, which are a particular type. To build them, excavations are made and filled with lean concrete, leaving only the upper part where structural concrete is used to build a footing. It is used when the most superficial layers of the soil are too soft, but firm ground is found at a depth of less than 10 meters. However, to use this type of foundation, it is important that there is no nearby water table that could negatively affect the structure.

DEEP FOUNDATIONS

Deep foundations are structures characterized by having their contact with the ground at a depth greater than 8 times their diameter or width. These structural elements are used when the resistant stratum is at a great depth below the soil surface, allowing for efficient transmission of loads at depth.

According to the CTE DB SE-C, deep foundations can be classified into the following types: isolated pile, pile group, piled zones, or micropiles.

In addition to this classification, deep foundations can also be grouped according to other criteria, such as the material used in their construction, the shape of the piles’ cross-section, the diameter, or the construction procedure employed.

– Piles

Piles are characterized by having a conventional diameter, greater than 300mm and less than 800mm. According to the Technical Code, piles can be classified into three main categories: isolated piles, pile groups, and piled zones.

An isolated pile is located far enough away from other piles so that it has no geotechnical interaction with them. On the other hand, pile groups, due to their proximity, interact with each other or are joined by rigid structural elements, allowing them to work together and distribute loads more efficiently.

Piled zones are areas where piles are arranged for the purpose of reducing settlements or improving safety against sinking in foundations. These piles usually have a limited individual bearing capacity and are located regularly or at strategic points.

In addition to the classification, it is relevant to highlight the categorization according to the construction procedure, which differentiates between driven piles (or displacement piles) and “in-situ” cast piles (or replacement piles).

Driven piles are hammered into the ground under pressure, improving its density and without the need for soil extraction. In contrast, “in-situ” cast piles require excavation to be installed, which decompresses the soil.

– Micropiles

Micropiles are a type of pile with a diameter of less than 300mm. They are composed of a metal reinforcement formed by tubes, bars, or profiles inserted into a small-diameter borehole. In some cases, they may be injected with mortar grout under pressure to improve their load capacity. Their usual length is 10 meters, although it can vary from 6 to 26 meters.

Some of their applications include underpinning foundations to repair them or increase their load capacity, in new foundations on sites with limitations on the use of conventional piling machinery, and in discontinuous diaphragm walls.

Retaining walls

If the ground to be built upon is on a slope, it will be necessary to implement an earth retention solution with retaining walls.

For this purpose, retaining walls will be used, a type of construction element that supports the horizontal pressure of the earth it contains to prevent its displacement.

There are various earth retention systems, so to determine the most suitable one, it is necessary to evaluate factors such as the type of terrain, the amount of earth to be contained, and the type of structure to be built on top, in addition to environmental aspects.

Retention elements can be classified according to their way of working into three main categories: gravity walls, self-supporting walls, and diaphragm walls. [10]

– Gravity walls

This type of wall resists horizontal stresses with its own weight. In some cases, they do not require a foundation but rest directly on the ground. They are mainly used to contain earth in outdoor spaces without structures on top.

They can be made of discontinuous elements, characterized by their drainage capacity, such as dry stone, prefabricated blocks, gabions, or reinforced earth; or they can be continuous, made of mass concrete or masonry.

The dry stone wall is noteworthy for being one of the most traditional. It is a wall composed of stones without cement mortar, obtaining its strength thanks to the geometry of the stones. Although it is a traditional wall, it does not support significant loads and requires specialized labor, which limits its use in building construction.

Prefabricated block walls use materials such as concrete, ceramics, or stone, and differ from dry stone walls by the use of cement and, in some cases, reinforcement. Finally, gabion walls are composed of metal cages forming containers filled with small stones, and reinforced earth walls are composed of earth reinforced with a steel mesh that prevents earth from falling away, which is very interesting for its low visual impact.

– Self-supporting walls

Self-supporting walls, in addition to supporting ground loads, have the capacity to hold structures on top of them. Therefore, they are usually built with reinforced concrete, either cast on-site or prefabricated. Due to their function of supporting more loads, these walls tend to be more deformable, so they require a suitable foundation. There are two main types of self-supporting walls: cantilever walls and counterfort walls.

Cantilever walls are characterized by having a base, either in the form of a toe, a heel, or both, which prevents the wall from overturning. This addition to the base provides greater stability and resistance to the lateral forces of the contained ground. On the other hand, counterfort walls are similar to cantilever walls but include counterforts. These counterforts are necessary when the height of the wall and the contained earth exceed 5 or 6 meters, which can generate a risk of overturning or collapse, thus adding stability and safety to the structure.

– Diaphragm walls

Diaphragm walls are structures that are embedded in the ground without having a horizontal base. This lack of base is compensated by anchoring the wall to the ground using cables.

An advantage of diaphragm walls over gravity walls is that they significantly limit deformations. This is due to their ability to resist the lateral pressure of the retained soil.

It is important to highlight that diaphragm walls are a versatile system, as they can be used both for earth retention and for discontinuous deep foundations using micropiling.

If we analyze foundations with sustainability criteria, we realize that it is necessary to regulate the use of plasticizers and other toxic and polluting additives, as well as to take into account the impact of grout injections, which can cause alterations in groundwater. There are more sustainable alternatives, such as the use of cast or prefabricated concrete, which guarantees a lower impact construction.

PHASE 4. STRUCTURE

Once the foundation phase is completed, the construction of the building’s structure proceeds, which plays a fundamental role in defining the space and the final sense of comfort.

According to the CTE Basic Document on Structural Safety, the structure must meet two basic requirements to be suitable. Firstly, it must possess adequate strength and stability to avoid undue risks, both during the construction phase and for the intended uses over time. Secondly, it must be fit for service, avoiding inadmissible deformations during its use. [11]

The structure of a building is determined considering the intended service period, requirements regarding bearing capacity, the actions considered and the safety coefficients used, the mechanical characteristics of the structural materials, the overall geometry defined by the structural elements, and the calculation methods used.

Depending on the type of elements used, the most suitable material will be selected, which affects the mechanical characteristics of the structure and also conditions the construction method. Depending on the material, the structure can be “in-situ”, i.e., built on-site, or prefabricated and dry-assembled.

Depending on the material used, we can distinguish mainly between concrete, masonry, steel, timber, and even adobe structures. These last two stand out in terms of sustainability.

However, the most common classification of the structure is based on its way of working. The different types of elements that define the geometry of the structure can be vertical, such as walls, pillars, and occasionally tie rods, or horizontal, such as floor slabs, beams, and arches. Vertical elements transmit loads vertically towards the foundation, while horizontal ones distribute and transmit loads towards the vertical elements. [12]

From these elements, the following two structural systems are configured at a general level:

– Load-bearing wall structure

In this structural system, vertical loads are supported by load-bearing walls, which are elements designed to distribute loads superficially. Their main function is to support both the upper floor slab and their own weight, while simultaneously defining and dividing the interior space. In addition, they also fulfill the function of earth retention.

There are two types of walls in this system: load-bearing walls, which directly support the floor slab, and bracing walls, which are arranged perpendicularly to the load-bearing walls and allow for resisting horizontal forces.

The choice of material used for the walls can vary, including concrete, masonry or thermo-clay, timber framing, and even adobe, which influences the on-site execution. However, during the execution of this system, the load-bearing and bracing walls are built simultaneously, ensuring that the floor spans do not exceed 8 meters.

During the construction phase, it is essential to wait and verify that the load-bearing walls have reached sufficient strength before loading them with the weight of the floor slab.

It is important to mention that these structures usually have a considerable thickness due to the various forces they must support. If the thickness is reduced and the slenderness of the walls is increased, buckling problems could occur.

– Frame structure

The frame is a structural system composed of two linear elements: beams and pillars. The beams rest on the pillars, transmitting the loads to them, while the pillars, in turn, transmit these loads towards the foundation.

This system is characterized by its separation between the structural function and the enclosure function. The pillars can be built of different materials and present different sections. The most common are concrete or timber with rectangular or circular sections, and they can also be steel with H-shaped profiles.

Beams are responsible for resisting loads perpendicular to their axis. There are main beams, which rest directly on the pillars, and secondary beams, which rest on the main ones. These beams are usually made of concrete, steel, or timber and allow for the creation of open spaces with large spans.

The construction process of this system begins with the placement of the pillars on the foundation. Once raised, the beams are built or placed on top, followed by the floor slab of the first floor. If the building has more levels, this process is repeated. It is important that the pillars have continuity between them to guarantee the stability of the structure.

The joints between the beams and the pillars can be hinged, so that the beams only transmit vertical loads to the pillars, or rigid, which allows the beams to transmit both vertical loads and moments.

As for the thickness of the enclosure walls, it can be less than that of the load-bearing walls, although this depends on the thermal and acoustic requirements of the building.

– Floor slabs

Floor slabs are structural elements that resist the superficial loads acting on the floor of a home and transmit them to the vertical elements, such as walls or pillars. In addition to this function, floor slabs also brace the vertical elements, contributing to the stiffening of the structural assembly against horizontal actions.

Fundamental requirements for floor slabs include the formation of a usable horizontal surface, stability, rigidity and compatibility of deformations, working as a monolithic whole, adequate thermal and acoustic insulation, watertightness, fire resistance, protection and durability, as well as economic and environmental sustainability.

In terms of classification, the structural behavior of the floor slabs can be considered, i.e., the direction in which they transmit loads. In this way, one-way and two-way floor slabs are distinguished.

One-way floor slabs transmit loads in a single direction, defined by their resistant elements, such as joists, ribs, or slabs. The space between these elements is filled with infill pieces, such as hollow blocks, planks, or lightweighting blocks. Some common examples of one-way floor slabs are those with timber, steel, or concrete joists, in-situ reinforced concrete ones, hollow-core slabs, profiled metal decking, and composite decking.

On the other hand, two-way floor slabs transmit the load in two directions, using resistant elements in both directions, forming a grid. These floor slabs are composed of linear elements in two directions and lightweighting pieces, such as coffers. Some notable examples of two-way floor slabs are prefabricated or on-site finished solid slabs, and waffle slabs or lightweighted slabs.

The diversity of structural systems and their possible combinations offers various options, such as one-way floor slab systems supported on walls or frames, or two-way floor slab systems supported on walls or pillars.

Now, if sustainability is placed at the center, seeking to reduce the CO₂ footprint both in the construction phase and during the project’s useful life, there are three outstanding construction systems that use natural materials such as timber or masonry.

Timber is a sustainable, renewable, and natural material that allows for the construction of highly efficient construction systems, facilitating the creation of passive houses with bioclimatic strategies. In addition, timber constructions usually have faster assembly times, making them advantageous compared to other traditional construction systems.

However, it is important to consider factors such as humidity, as it could affect the mechanical properties of the timber. For timber to be an economical and sustainable material, it is recommended that it be obtained from local sources or as close as possible, which not only implies energy savings but also promotes the local economy.

LIGHT TIMBER FRAMING

This structural system resembles that of load-bearing walls, but instead of using timber load-bearing elements, it employs studs of reduced sections. These studs are placed at a close distance from each other, generally between 1 and 1.5 meters, and are fixed using staples and nails to battens that form a frame. Finally, this frame is closed with timber or fiber panels, creating a lightweight load-bearing wall system.

A distinctive feature of this system is that in the space between the studs, cavities are formed that can be used both for placing insulation and for incorporating installations. To speed up construction, the framing system can be prefabricated in a workshop and then transported to the site, facilitating and accelerating assembly at the construction site.

Regarding materials, for the studs and battens, solid wood from conifers such as different types of pine and hardwoods is usually used. The panels are usually made of OSB, which are boards produced by joining sawdust with adhesives applying pressure and heat. In any case, the type of timber used must be defined in the CTE Timber Basic Document. [13]

A suitable type of floor slab for this framing system could be a one-way floor slab with timber joists. This system takes advantage of timber as a sustainable and efficient material for the construction of lightweight and durable structures.

CLT

CLT (Cross Laminated Timber) is a modern material that uses a wide variety of timber species and qualities to manufacture high-strength boards. It is a structural system of cross-laminated timber walls that works like a load-bearing wall system. [14]

These cross-laminated timber walls are composed of glued timber layers, subjected to pressure and placed in such a way that the fiber direction of one layer is perpendicular to the next, a fact that provides its high strength.

According to the CTE-DB-SE-M, the most commonly used timbers for this system are pine and spruce, and combinations of these. The layers usually have a thickness between 20 and 40 mm and are dried until reaching a moisture content of 10-14%. This favors adhesion and reduces dimensional variations and cracking. In addition, if the thickness is sufficient, installations can be incorporated within the panel, similarly to lightweight framing. [15]

CLT allows for building taller, stronger, and more stable timber structures. It also offers the possibility of better quality and more sustainable buildings thanks to prefabrication and speed of assembly, as well as the savings in foundations it entails. It is a possible option for floor slabs and roofs, as it allows for generating wider spaces and its on-site installation is fast and dry. [16]

MASONRY

Masonry is one of the most traditional construction techniques. This system is based on the use of small elements such as bricks or blocks, mainly composed of clay and water, generally joined by cement mortar. Masonry is mostly used in load-bearing wall structures, although it is a more laborious system for on-site execution compared to timber systems.

Masonry pieces can have different sizes and can be solid, perforated, or lightweighted, depending on the required strength and the type of wall to be built.

In the case of load-bearing walls, the minimum thickness will be 115 mm, although in general, this thickness is greater, reaching 300 mm in exterior walls, where two leaves of ceramic pieces are used and insulation or an air cavity is added.

An advantage of this system is the wide variety of exterior finishes it allows. The use of small pieces of different sizes and textures enables various brick placements, called bonds. In addition, mortar joints can also be made in different ways, such as flush, recessed, or protruding, which adds more finishing possibilities.

However, this system may require bracing in some cases, which implies greater compartmentalization of space, limiting spans and making the openness of the whole difficult.

Currently, highly sustainable construction systems based on 100% recyclable materials with low economic and energy costs have been developed. A prominent example is the use of compressed earth blocks (CEB).

These construction blocks are manufactured using a mixture of earth, sand, lime, cement or clay, and water, which is subsequently subjected to compression in a compacting machine.

CEBs are a non-toxic and environmentally friendly option. They are renewable materials that offer good acoustic insulating properties, are breathable, and fire-resistant. In addition, their walls can act as heat and solar energy storers, releasing it when temperatures drop.

Although this system is included in the UNE 41410 Standard for Compressed Earth Blocks for walls and partitions, they are still in the process of commercialization. However, their sustainable potential and characteristics make them a promising option for the future of construction. [17]