Development of a Generative Design System for 3D-Printed Houses in Chile

Abstract

Three dimensional-printing construction is an emerging technology with significant potential for faster building execution and more precise, controllable designs. This technology utilizes material deposition managed by computer data, enabling additive construction of shapes. This research aims to develop a generative design system for 3D-printed houses in Chile, addressing the country’s growing demand for housing across diverse geographical locations and social groups, also present in other parts of the world. The development process involves synthesizing the external form features of existing Chilean houses and analyzing prototypes of 3D-printed houses worldwide to establish a set of geometric characteristics suitable for 3D-printed homes in Chile. A procedure is then outlined to create design alternatives using parametric programming on a BIM platform, followed by toolpath development for printing the building components. Various models are generated to demonstrate housing shapes’ versatility and adaptability to Chilean contexts and 3D-printed construction methods. Finally, a detailed design is created and printed to construct a housing prototype, testing the entire digital workflow. This experience highlights the variety of 3D-printed housing shapes that can be developed while assessing their feasibility for the Chilean context. This research complements the flexible design capabilities of 3D printing construction, resulting in buildings better suited to various locations and occupancy needs.

1. Introduction

There is a high global demand for housing, necessitating mass production while accommodating diverse local conditions. Three dimensional-printed construction, an innovative additive technology, enables rapid and versatile building forms through digital control of design and construction [1]. While various experimental homes and some residential complexes have demonstrated the capability of this technology, they have not fully explored its potential for design variety [2].

The codification of geometric characteristics in architectural design has been a focus from classical treatises to contemporary digital processes. This work presents a strategy for generating 3D-printed housing forms to promote the use of this technology in residential construction, particularly in Chile. Like in many countries around the World, Chile has sustained residential production characterized by significant climatic variety, structural requirements, and social diversity, which necessitate diverse housing designs [3].

The design conditions considered in this research are based on the geometric properties of existing houses in Chile and experimental 3D-printed houses worldwide. Consequently, a set of rules codifying the characteristics and variations of house envelopes was established and implemented in the parametric design to define geometrical variation, enabling the generation of adequate residential forms. One of these designs was then executed as a prototype 3D-printed house with the support of local companies. This effort demonstrates the architectural diversity possible with 3D-printed technology, promoting its application in residential construction worldwide.

1.1. Background

Since the post-war period and the spread of modern architecture, massive public and private housing programs have been developed in many countries with a similar repertoire of forms and construction typologies. In Europe and Asia, the focus has been mainly on high-rise residential concrete buildings, and in Latin America, low-rise buildings have been combined with detached or attached housing made of blocks or bricks. Housing production has remained low in industrialization and with similar designs [4].

Chile has approximately six million housing units, accommodating one-third of its population, with an average of three residents per unit. According to current government categorization, these units are distributed between single-family and collective homes [5]. They are typically constructed using reinforced concrete, reinforced masonry, and wood or metal frameworks, like many emerging countries. The annual production of housing is nearly 1.8% of the total existing units, equating to approximately 100,000 homes annually. This production mainly consists of high-rise or large complexes promoted through various public programs that fund housing for low-income residents and private sector operations involving diverse actors and regulations [6]. Figure 1 shows a regular housing development in Chile.

Residential construction in Chile has progressively increased in productivity, sustainability, and quality through technological evolution and commercial development. This advancement addresses growing urbanization in cities across different regions, each with significant geographical disparities and high structural requirements [7]. The country spans an impressive latitudinal range (17.3° to 56.3°) with narrow elevation variations from sea level to 2500 m within 180 km. Consequently, 18 distinct climate types have been identified as the ones to which housing development projects must adapt. Additionally, Chile’s location in a tectonic plate convergence zone, with numerous volcanoes and extensive coastlines, requires buildings with high seismic resistance. Chile has also experienced sustained socioeconomic development, demographic transformation, and cultural progression, driving diverse housing demands [3]. This situation is paradigmatic of an emerging country with significant constructive capacity and diverse housing requirements. The challenge lies in adopting digital design and manufacturing technologies, specifically BIM-modeling and 3D-printed construction, within a workflow that addresses residential development needs.

In recent years, over a hundred experimental 3D-printed constructions have been executed worldwide, primarily consisting of single-family homes and, in a few cases, larger buildings or complexes [8]. These 3D-printed houses feature a variety of shapes, some resembling conventionally built homes and others with unique geometries, typically including rounded corners and curved profiles for easier printing and enhanced stability [9]. While walls are the primary printed elements, roofs, floors, furniture, and stairs are occasionally printed as well. The printed components often have a rough finish due to the layering process, though exposed faces are sometimes coated for a smoother appearance. Steel reinforcements are usually integrated into the printed elements, along with conventional doors, windows, installations, and finishes to complete the building [10].

Most 3D-printed construction projects have utilized cement-based mixtures due to their high industrial capacity, fine aggregates, and additives that provide adequate fluidity and accelerated hardening, resulting in significant strength. Ongoing research is exploring the use of recycled aggregates and organic mixtures to reduce the environmental footprint. A few 3D-printed housing complexes have been erected, often featuring identical designs for different units to simplify management. However, some proposals highlight the potential for varied house forms [11].

Notably, most 3D-printed houses have been constructed in warm areas, without significant climate or structural requirements, serving primarily as experimental units for technology testing and promotion. Some providers have proposed different housing designs, emphasizing the potential for design flexibility but without developing its possibilities.

These capabilities suggest the formulation of industrialized systems that consider design alternatives and management through digital design related to 3D-printed construction. Leveraging geometric principles to organize design and construction, the approach proposed in this article enables the creation of variable shapes and advances toward open industrialization or mass customization, with automated execution facilitated by 3D printing.

1.2. State of the Art

Three dimensional-printed construction enables the extrusion of mixtures to create large elements by layering horizontal layers, making it suitable for quickly executing volumetric elements by perimeter or infill, thus avoiding supports and several conventional tasks. The extrusion process is controlled by automated equipment to ensure precision. The toolpath for printing, which defines the extrusion track, is generated from a digital design, allowing modifications to enhance stability and production speed [1]. Various 3D-printed construction technologies are currently being developed through university research and commercial enterprises, utilizing six-degree-of-freedom robots or 3D gantry systems with different mixtures and construction strategies. Including off-site printing of building elements and on-site printing. The former can be achieved in a factory with static machinery with printed parts shipped to the site, whereas the second requires machinery to be moved around the site or from site to site to print parts in place. Concrete extrusion has been particularly experimented with in walls, forming low-rise buildings to demonstrate its operational advantages [2]. Housing units can be designed and executed to promote faster construction, reduce costs, increase sustainability, and improve detailed management.

Scientific documentation on 3D-printed construction highlights design flexibility, emphasizing the need to systematize shape definition and information transfer for execution [12,13,14]. Some studies suggest organizing design variation for automated execution based on shape grammar with constructive adjustments [15] and linking to building information modeling [16] or specific element printing [17]. The digital information flow between design and 3D-printed house construction [18] has also been emphasized, though often without considering geometric diversity. The standard for additive manufacturing [19] outlines actions from design to execution, addressing data processing from geometric model creation and segmentation to define a printing toolpath, with geometric adjustments for element feasibility before printing. The standard [20] complements this process, emphasizing design verifications such as edge thickness and temporary supports without considering design systematization or variation.

Housing design systems typically consist of geometric grids, locating rooms, and partitions to define residential units, with various compositions and similar elements that can be industrially prepared [21]. Architect Edwin Haramoto proposed a housing design process in Chile that considered subsequent growth and promoted industrialized diversity [22]. This housing production strategy has recently been renewed with the concept of “mass customization” [23]. Some processes for variable housing design with computer programs [24], integrating prefabrication managed with Building Information Models (BIM), a new standard that integrates digital design and construction data [25,26], have been experimented with, though without covering 3D-printed construction. A conceptual framework has also been proposed to integrate mass housing production with specific requirements [26] through digital design and manufacturing technologies, emphasizing the flexibility and adaptability of housing solutions. Likewise, Muthumanickam et al. [27] developed a BIM-based platform, like a suite of software tools, to design and print an optimized 3D-printed habitat. However, there has been limited advancement in developing and testing these proposals.

Therefore, it is pertinent to formulate variable design processes that can be incorporated into housing production using new 3D-printed construction capabilities.

1.3. General Housing Design Process

Housing design entails a series of progressive stages of geometric definition driven by the specific units and spaces needed at the site. Typically, this process begins with the design of the housing complex on the site, followed by the definition of the three-dimensional shape of each house (mass volume), and continues with the organization of interior spaces (room layout). During these phases, occupant participation is occasionally considered, and local requirements and cultures are often taken into account.

In current practices, most tasks are carried out on digital drawing and 3D modeling platforms that enable the generation of realistic visualizations and technical construction details. Building conditions, including costs and planning, are usually considered when defining the design. In 3D-printed construction, after defining the volume and layout, the geometry of some elements must be translated into a toolpath for the equipment. This culminates in the 3D-printing execution, where automated machines make the building elements. This process creates a seamless digital information flow that integrates design and construction, aligns with user requirements and printing equipment constraints, and enables ongoing monitoring of development. Figure 2 illustrates this process. This work focuses on the systematization of the exterior volume of houses (step 2 in the figure), a crucial aspect of the architectural definition, aesthetic expression, urban adaptation, functionality, and construction execution. The significant variation allowed by 3D printing makes exploring shape alternatives feasible.

2. Methods

Given the exploratory nature of this study, and with the aim of quickly piloting the capabilities of the developing system, three phases of methodological development are proposed. First, the geometrical characteristics of the houses designed and built in Chile are presented. Next, the programming developed for the computational implementation of the system is described. Finally, the main aspects considered for carrying out the prototyping of a case study are outlined.

2.1. Synthesis of Formal Housing Conditions

The characteristics of the housing volumes for the proposed system are determined by comparing the geometric features of houses in Chile with prototypes of 3D-printed houses worldwide. This strategy aims to connect construction experience in a specific context with emerging technological capabilities.

The shape of houses in Chile, as in most parts of the world, is determined by construction systems, functional requirements, economic capacity, site features, urban regulations, and cultural and climatic conditions. Various residential density typologies range from single-family homes, with one to three floors, grouped in isolated, attached, or continuous arrangements, to multi-family buildings with different numbers of floors, mostly integrating several apartments on each floor. Apartments are mainly located in large urban centers, while houses are found in the peripheries of cities or rural areas.

The study of housing typologies in Chile is not new. Vergara et al. [28] examined the document “Rationalized Housing Typologies 1966–1972”, which illustrates how the design teams of the State Housing Corporation (CORVI) aimed to streamline interactions in the selection, construction, and habitability of social housing by standardizing materials, programs, and housing types. In another study [29] using Rafael Moneo’s definition of “typology”, which describes a group of objects with the same formal structure, the study identifies three typological strategies developed by CORVI: paired houses, isolated blocks, and high-rise residential buildings. Haramoto, Jadue, and Tapia [30] and Tapia [31] also account for these formal typologies, reflecting an exercise of standardization and individual flexibility in the design of low-income housing, whose traces persist to this day.

The sizes of dwellings in Chile, as indicated by built area (which usually establishes their functional capacity and construction cost), range from 18 m² to over 200 m², with an average of approximately 70 m² according to formal records of construction. This size often increases over time due to extensions, especially in houses. Interiors are typically organized by rooms, according to the total area, particularly the number of bedrooms, with a central longitudinal and/or vertical circulation that has little impact on the external volume. Openings to the outside are usually distributed homogeneously and centrally by room, in proportions of 15 to 20% relative to the opaque surface, increasing in living rooms, decreasing in bathrooms, and occasionally leading to the outside. Housing volumetry is regulated by its urban situation (site context) and some interior conditions, such as minimum areas per room or furniture in state-financed housing. Additionally, the thermal transmittance of envelopes by climatic zones is regulated, and in some urban areas, the size of openings and climate control systems are defined. Despite these regulations, formal similarities are maintained in very different geographical locations and cultural contexts due to construction massification, even though vernacular architectures are very dissimilar and currently reflect social diversities and demographic transformations.

Single-family homes and apartments in multi-family buildings typically feature orthogonal volumes, often with a rectangular base and side proportions of 1:2 (width to length). Occasionally, one or two volumetric setbacks on some facades create an L or Z profile in the footprint or plan. In larger residences, stepped configurations may be used to change the floor area, usually to reduce the area at higher levels. Significant extensions, separations, or interior patios are rare. Roofs in single-family homes can vary in slope and composition, sometimes affecting the lateral shape of interior spaces. Multi-family buildings mostly have flat floors and roofs, with sloped roofs occasionally seen on the top level. This formal variety is similar to that found in many countries, though there are some differences in sizes and heights.

In contrast, the prototypes of 3D-printed houses and the few housing complexes built with this technology display more diverse shapes. These structures are typically single-story with reduced areas ranging from 12 to 70 m² and rarely extend to two or more levels. Some volumes resemble conventional houses with rectangular shapes and sloped roofs, either printed or made of another material. These designs often feature rounded corners to facilitate edge execution by the extruder nozzle, resulting in visibly rough walls. Other houses exhibit circular or curvilinear volumes, particularly in the horizontal profile and occasionally in the vertical profile, including parts of the roof. These may also have flat or sloped roofs made from other construction systems, either separated or with independent supports.

Many designs combine straight interior parts with curved exterior parts, especially in living rooms, to enhance spatial and expressive novelty. This integration often requires incorporating conventional construction elements, urban insertion, or furniture support, which can be challenging with curved shapes. Interior spaces usually reflect this formal diversity, maintaining a conventional organization with occasionally larger living rooms and reduced circulation areas. Openings are typically smaller in height, avoiding lintels or spanning entire wall sections.

In summary, typical houses in Chile exhibit orthogonal shapes with regular and/or partially recessed profiles of various sizes, floor variations, and similar interior arrangements. In contrast, 3D-printed houses are generally smaller and single-story, yet they display greater formal diversity in their horizontal and vertical profiles. Therefore, a repertoire of straight and curved volumes with diverse profiles, sizes, and floors can encompass both the conventional housing forms in the country and the potential of 3D-printed construction (

Table 1. Summary of housing shapes features.

Features	Regular Housing in Chile	Three Dimensional-Printed Prototypes	Housing Features for the System
Volume	Single-family Isolated, Attached, or Continuous Multi-family flats in buildings with 4 to 20 stories	Single-family isolated, a few examples attached or multi-family	Single-family isolated, possible to be attached or vertical superimposed
Unit Stories	Flats mostly one-story Houses, mostly two stories, someone or three, reducing built surface in height	Mostly one-story	one, two, and three stories
Total Surface	From 18 to 240 sq.m., average 90 sq.m.	Mostly from 20 to 60 sq.m.,	From 9 to 300 sq.m
Geometry	Mostly straight	Straight, Curve, or Mixed	Straight, radial, or mixed
Layout	Compact, mostly extended 1.2–1.5 length/wide	Compact, mostly square or circular, some extended 1.2	Compact 1:1 until extended until 1.6
Profile	Few basic, mostly L-shapes, others T, Z, or complex	Most basic or low complexity	Basic, L-shape, and Z-shape
Walls	Vertical	Vertical and some tapped or curves	Vertical, tapped, or curved
Roofs	Mostly Double-pitched or Complex-pitched, few planar	Planar, double-pitched, vaults, domes	Planar, double-pitched, vaults, domes
Corners	Mostly straight	Mostly rounded, some straight	Straight or rounded

).

2.2. Programming

The shape generation process was carried out in the 3D modeling software Rhinoceros Version 7 SR20 (7.20.22193.9001, 2022-07-12), usually used for creating precise, complex, and detailed geometries, using the Grasshopper programming utility for parametric design, which is a visual programming language to generate and control shapes that run within Rhinoceros. Parametric components with embedded geometric operations and numeric controls were applied to create variable volumes based on the previously reviewed conditions. Within Grasshopper, tools for generating and controlling geometries were established, employing plug-ins such as HumanUI, Pufferfish, Metahopper, and Telepathy. These plug-ins facilitated defining distant connections and input/output data panels, enabling interactive volume creation through parametric measurements (

Table 2. Grasshopper plugins used in the programming for the parametric design.

Plugin	Primary Use	Key Features	Selection Criteria
HumanUI	User interface design	Interactive UI elements	User friendly real-time parameter manipulation and data visualization within grasshopper
Pufferfish	Advanced geometries	Morphing	Ability to solve complex geometric problems
Metahopper	Grasshopper script management	Dynamic handling of grasshopper components	Dynamic constraints for parameters
Telepathy	Grasshopper script management	Remote data access	Wireless communication between components for easy programming and data management

).

Parametric programming is organized by generating a volume consisting of three horizontal levels, defined by three overlapping quadrilaterals. Each quadrilateral is specified by the dimensions of its parallel sides, such as length and width (ranging from 3 to 10 m, with increments of 0.1 m). One corner is fixed to ensure two perpendicular sides on all three levels, facilitating urban attachments. The remaining sides can extend with different dimensions on each floor, creating horizontal offsets. Additionally, the plan can have a rectangular profile, maintaining the basic rectangle; an L-shaped profile, by extending part of an edge in both orthogonal directions; or a Z-shaped profile, by extending two lateral parts of opposite sides. For L-shaped and Z-shaped profiles, an additional dimension for each side is added on all three levels (similar on both sides for Z-shaped profiles). The height between levels varies from a minimum residential height of 2.3 m to a maximum height of 3 m.

Two shape families are considered: one with orthogonal flat faces commonly used in conventional construction systems and another with curved faces more frequently applied in 3D-printed construction. Straight volumes are created by vertically extending each edge of the plan silhouette as a perpendicular extrusion, while curved volumes are created by defining a circular arc between consecutive vertices of the plan. The distance from the edge to the midpoint of the arc determines the curve’s nature: a negative value results in an inward or concave curve, and a positive value results in an outward or convex curve, with arcs proportional to the edge length. Three profile types are defined to extend the vertical faces: Straight, Bubble, and Cushion. In the Straight profile, vertical planes are raised perpendicular to the base plane. The Bubble profile raises vertical curved planes at each level with a concave or convex arc segment according to a regular horizontal magnitude. The Cushion profile involves a set of two or three floors, with the arc spanning from the base to the upper level. An extension (loft) application in the vertical profile generates an inclined plane between the edges of the offset levels, whether straight or curved, according to the shape typology, creating continuous profiles between the inward or outward floors. The variation of curvature and inclination allows for the generation of continuous or discontinuous profiles. The combination of a curved profile and a curved plan enables the creation of volumes with double-curved surfaces. Additionally, the vertical junctions of the horizontal sides of each level can be modified by diminishing the length of each side according to a variable radius and rounding the corners in plans, which is common in printed houses.

The program’s execution was tested by operators independent of the programmer, who used the control panels in the 3D design software Rhinoceros Version 7 SR20 (7.20.22193.9001, 2022-07-12) to generate a variety of volumes and provided feedback on execution conditions. The generated designs were documented according to variations and combinations, noting dimensions and saving images from similar viewpoints to create design repertoires. Additionally, the program’s functionality, usability, geometric consistency, adherence to established conditions, and spatial expression of the generated volumes were reviewed using aerial and pedestrian views as well as scale model printing. The linkage with the BIM platform was also tested, operating simultaneously with Rhino.Inside^® and Revit for geometry export, architectural and construction modeling, and programming printing paths for execution.

To complement the volume programming and create a full-scale material prototype, one of the smaller surface shapes on a single level was detailed to combine straight and curved profiles. The wall lengths were determined by considering the formation of rooms, continuous or small inserted openings, and the maximum transportable length since the printing was performed in a factory. A structural strategy with seismic resistance was implemented, featuring reinforced columns within wall segments, a base, and a top beam, additional steel connections between wall sections, and thermal protection suitable for a temperate-humid climate, according to local regulations. The printing path for each wall was developed according to the equipment specifications, and an execution plan was devised. For this design, radius dimensions and distances between axes were used for the layout, allowing variations in its plan extension while maintaining the overall arrangement.

2.3. Prototyping

To verify the application of the formal conditions, test the printed execution, and promote these technological possibilities, a prototype house was developed with the support of a local real estate company. A 30 m² housing example was agreed upon, roughly half the average house size in Chile, yet sufficient to include an entrance, living room-kitchen, bedroom, and bathroom. A single-story design was chosen for ease of execution, with a longitudinal proportion to highlight its volume and a floor plan combining straight and curved edges to showcase various geometric capabilities. The chosen form was developed in a BIM model to detail its components, including foundations, walls, and openings. Openings were strategically placed based on room function and solar orientation, featuring large windows on the sunny side and smaller windows with the main entrance on the shadier side.

The printed walls and other minor elements were created in a university campus laboratory using a BemorePro printer with a capacity of 6.5 m in width, 3.5 m in height, and 12 m in length, equipped with a PFZ pump of 120 L and Lafarge Tector mix. Due to transportation constraints, the wall sections were divided into pieces weighing less than 1,500 kilos and up to 3 m in length. Double-cord walls were designed to accommodate thermal insulation, structural reinforcements, and installations within the cavity. Exposed printed faces received additional coating protection while maintaining a rough appearance.

A seismic-resistant analysis of the house model was conducted, establishing interior columns within the walls, reinforced concrete lower and upper tie beams with metal bars, wall sections and joints with adhesion bridges, and metal connection beams between wall sections. Detailed plans were created for the foundations, roof metal structure, electrical installation, and various finishes for walls, floors, roofs, and exteriors. A construction plan and promotional images of the house prototype were also prepared.

The shapes of the wall sections were transferred to parametric design software to program the extrusion toolpath and generate the printing code to control the machinery for execution. On-site work, including foundations, assembly, roofing, and finishes, was carried out by a construction company designated by the real estate firm. The execution of the walls and printed elements was managed by the research team, who also oversaw the complete design, construction supervision, and post-construction management aimed at dissemination and monitoring. Additionally, the processes, work times, and feedback from visitors were reviewed.

3. Results

3.1. Geometric Characteristics of Shape Generation

The geometric conditions derived from integrating regular houses in Chile with prototypes of 3D-printed houses worldwide inform the development of a central volume suitable for isolated single-family homes. This house typology is prevalent in 3D-printed construction due to its ease of execution and visibility, and it mirrors common designs in the Chilean residential repertoire. These volumes can also be applied to attached or continuous housing, although there are some formal restrictions, such as orthogonal sides and total width limitations. Additionally, they can be adapted for apartments in collective buildings, requiring structural adjustments and grouping. Volumes ranging from one to three levels are considered, although multi-level 3D-printed houses are relatively rare due to structural challenges and the complexities of integrating floors and stairs. While many 3D-printed house prototypes are smaller due to experimental constraints, larger dimensions are feasible. The scope includes small residential units, such as one-bedroom cabins or integrated spaces, as well as larger homes with two or three floors.

Both orthogonal volumes, which align with traditional house shapes, and curved volumes, suitable for 3D printing, are taken into account. Typically, compact volumes, similar to most conventional and printed houses, are considered, with proportions extending up to three times the sides and regular heights between levels. Plan profiles include frequent shapes found in existing houses as well as more diverse forms seen in printed prototypes, summarized into rectangular figures with one or two lateral extensions to cover significant variations. Corners are designed with options for either rectangular or radial vertices, accommodating the main configurations of both conventional and 3D-printed houses. Curved profiles follow regular arc procedures for each side and level, generating notable but controlled variations within a defined repertoire. Various vertical profiles between floors—orthogonal, inclined, or curved—are considered, reflecting patterns found in both traditional and printed prototypes, although primarily in single-story structures. More complex or detailed elements such as roofs, openings, minor components, or textures are not yet included, with the focus primarily on fundamental volumes that represent a significant portion of both existing and 3D-printed housing shapes.

3.2. Parametric Programming Process

The parametric programming process implemented using Grasshopper in Rhinoceros facilitates the creation of geometric volumes by adjusting various numerical controls. This enables manipulation, visualization, and data export within the design environment. The process involved iterative verification of parameters to organize and name geometric characteristics, impacting both the volumetric and exterior expression of the designs. Adjustments to definitions, programming, and parameter displays were made until the initial version was finalized.

The final implementation included twenty geometric parameters (

Table 3. Parameters contemplated in programming.

N°	Type		Parameter	Description	Type	Values	Step	Unit
1	Floor Profile	Orthogonal	R	Rectangular plan	Option	0–1	1	True-False
			L	L-shape plan	Option	0–1	1	True-False
			Z	Z shape plan	Option	0–1	1	True-False
2		Curve	C	Distance from each side to the central point of the arc	Integer	−2 to +2	0,1	mts
3	Floor Sizes	Main	L	Dimension of length side of first story	Integer	3 to 10	0,1	mts
4			W	Dimension of width side of first story	Integer	3 to 10	0,1	mts
5			L2	Dimension of length side of second story	Integer	3 to 10	0,1	mts
6			W2	Dimension of width side of second story	Integer	3 to 10	0,1	mts
7			L3	Dimension of length side of third story	Integer	3 to 10	0,1	mts
8			W3	Dimension of width side of third story	Integer	3 to 10	0,1	mts
9		Floor Extension	L’1	Dimension of length side of extension in the first story	Integer	0 to 5	0,1	mts
10			W’1	Dimension of width side of extension in the first story	Integer	0 to 5	0,1	mts
11			L’2	Dimension of length side of extension in the second story	Integer	0 to 5	0,1	mts
12			W’2	Dimension of width side of extension in the second story	Integer	0 to 5	0,1	mts
13			L’3	Dimension of length side of extension in the third story	Integer	0 to 5	0,1	mts
14			W’3	Dimension of width side of extension in the third story	Integer	0 to 5	0,1	mts
15	Heights	first	H1	First story height	Integer	2,4 to 3	0,1	mts
16		second	H2	Second story height	Integer	2,4 to 3	0,1	mts
17		third	H3	Third story height	Integer	2,4 to 3	0,1	mts
18	Vertical Profiles	Straight	S	Straight edge on each floor	Option	0–1	1	True-False
		Bubble	B	Three arcs, one on each floor	Option	0–1	1	True-False
		Cushion	H	Continuous arc on all three floors	Option	0–1	1	True-False
19		Section offset	SO	Distance from the vertical edge of each side to the midpoint of the external arc	Integer	0 to 2	0,1	mts
20	Corners	Radius	RC	Radius for rounded corners	Integer	0 to 2	0,1	mts

) designed to facilitate the rapid exploration of a wide range of design options. These parameters include formal alternatives or numerical values of measurements, some of which are interdependent while others are independent. The first parameter determines the type of floor profile applied across all three levels, while the second controls the magnitude of horizontal curvature on each side. Subsequent parameters specify the floor side measurements, starting with the central rectangular body at each level, followed by the lateral extensions for L and Z shapes. Additional parameters include the heights of each level, types of vertical profiles, curvature values, and the magnitude of the horizontal corner curvature in the floor plan profile (Figure 3). Some parameters are not applied or have a zero value in simpler forms. Numerical parameters are measured in meters, typically in increments of 0.1 m, with ranges set to produce volumes comparable to existing houses, ensuring visually significant differences.

The program developed in Grasshopper in Rhinoceros generates a series of geometries and closed volumes based on the parameters outlined in Table 2. Initially, the base parameters define the layout of the floor plans across three levels (Figure 3). From these layouts, volumes are created using extrusion and sweep operations through plan rail curves or transitions along curves, where wall section parameters define the resulting geometry (Figure 3). Logical operators are applied to alternate between different modes of form generation, utilizing the modeling methods available in Rhinoceros and enhanced by the Pufferfish plugin. The system incorporates surface measurement tools as feedback to assess the results. The final geometry is displayed as a closed volume, which is then used to apply element families according to Building Information Modeling (BIM) methodologies. From there, a slicing process is initiated, allowing the generation of trajectory curves for 3D printing.

The user interface of the program includes two panels, in addition to the view of the 3D environment in which the volume is created (Figure 4). One panel presents the design generation parameters with drop-down activation menus or numerical sliders (where the value can also be typed), which control the geometric definition, along with some explanatory diagrams of the parameters. A second panel presents output data with surface values per level, total area, and volume. Then, the software can be used by choosing options in the menu and manipulating numerical sliders in the input panel to generate geometries in accordance with the defined conditions. The model is shown in the visualization window, and numeric details are in the output panels. The image of the design and/or its geometrical data can be exported to other software.

Users encountered some challenges with the program, including delays in understanding and applying controls, particularly with minor definitions and curved parameters. Computational processing slowed numerical modifications, and some program functionalities were occasionally omitted or experienced stoppages. Users’ notes and memory were crucial for navigating these issues.

The final version of the program demonstrates improved stability and completeness, though it still experiences occasional stoppages and graphical delays. Notable pending enhancements include the ability to record forms and their assigned parameters, regularize operations, and advance developments in roofs, openings, interiors, construction details, and toolpath planning.

Visualization of models in the design environment offers flexibility in understanding volumetric forms, primarily through color and lighting. This visualization can be further enhanced by exporting the models to software with advanced visualization capabilities for a more detailed exploration of appearances and architectural detailing.

Additional tests of BIM integration and volume export for architectural development and generation of toolpaths were shown appropriate with some adjustments, mainly in dimensional configuration. Printing paths can be defined for each geometric element through slicing and perimeter continuity processes, assigning origin, direction, point discretization, and speed of the trajectory for printing. Complementary aspects were developed in the elaboration of construction elements, the definition of openings, spaces, and environments for visualization, and the development of layouts and toolpaths based on the user-specified initial shapes. This demonstrates the capability for digital integration and the fluidity of shape generation from design to construction.

3.3. Model Generation

The developed program enables the creation of various geometric volumes by modifying twenty established parameters, allowing for changes in shapes and dimensions. The resulting volumes can be displayed in either polar (perspective) or parallel (plan, elevation) views and maintain dimensions consistent with the specified parameters.

Combining options with the extreme values of each numerical range yields nearly a million different shapes. Many more variations can be generated with intermediate values, which can then be further elaborated in detail. For instance, one can create anything from a single-level quadrangular profile volume with side measurements of three meters, totaling 9 m² of built surface, to a similar volume with ten meters per side, totaling 100 m². This range of low and simple volumes aligns with a significant portion of the built forms in Chile, particularly for single-story, low-cost, or rural houses, as well as many simple apartments, which then vary in their interior layout, roofs, openings, and materials.

The program also supports generating two or three-level volumes, ranging from 18 m² on two levels with smaller sides to 300 m² on three levels with larger sides, including lateral extensions on both sides of the three levels (Z profile), reaching up to 450 m². Various intermediate variations are possible, especially with larger first levels and reduced second or third levels, stepped vertically. This diversity of forms resembles the basic designs of most urban houses in Chile, typically two to three stories high, with various minor articulations, roofs, and openings. They also resemble apartment forms with terraces, insets, and two floors. Some orthogonal volumes generated in one or two levels resemble printed houses assimilated into conventional residential designs.

The program also allows for generating volumes with rectangular or extended floor profiles with curved sides, either horizontally or vertically, with optional separations between levels and rounded corners. Some shapes created with these definitions, especially those with one level, small, compact (without extensions or with very small ones), and wide curved sides, resemble various printed housing prototypes. Some of these prototypes have circular profiles or combinations of curves and straight lines that the programming does not contemplate but can nonetheless be generated after minor geometric elaboration. Additionally, a diversity of forms is presented, especially in two and three levels, with concave curves, successive convex curves, or curved extensions, which seem feasible to print, offering new alternatives for printed houses.

Other volumes, particularly those with vertical curved continuities or very steep sides, may be challenging to execute due to the capacity of the mixture for horizontal cord displacement. Similarly, larger designs, whether in extension or height, may present structural complexities, equipment requirements, or construction challenges due to their size. Such designs may necessitate the use of partially printed elements fabricated in the factory and assembled on-site. Figure 5 illustrates some of the design possibilities enabled by the developed program.

The generated volumes correspond to the possible basic exterior form of houses without interior elaboration, roofs, or openings. These forms generally convey spatial centrality and a simple, symmetrical appearance, with prominent sides, mainly rectangular and taller volumes, and spatial variations in plan, curvature, or level differences. Lateral modifications suggest defining exterior entrances, balconies or terraces, and minor roofs. Completing the configuration and articulating the immediate surroundings of the house creates an interrelation between the exterior and domestic life.

Some forms, particularly those with projecting upper levels, express a distinct spatial hierarchy, which is rare in houses with mostly staggered floors. These designs may be more structurally and constructively demanding but also more unique. Similarly, volumes with multiple curvatures present an unusual expression, with silhouettes or planes that are slow to comprehend spatially, producing a progressive interpretation and variability from different observer positions. These forms articulate their surroundings and create a sense of distancing but may pose challenges in construction, occupancy, or maintenance.

The developed designs feature a concentrated interior, with various sides enhancing interior lighting and energy efficiency, though without a defined solar orientation. Central horizontal circulations or vertical stair cores and different rooms on the sides, especially in extensions, can be defined. The volumes can be grouped in plots, with designs selected based on the most extensive measurements to comply with urban regulations. Alternatives with straight sides or concave-convex combinations can be attached on one, two, or even three sides, including simpler options in multi-family buildings. The diversity of designs allows for combining similar ones, shifting positions, and providing different magnitudes for diverse occupants with various interior or exterior space distributions. The availability of geometric models for these alternatives facilitates the review of distributions and consideration of conditions to estimate mass planning with variety.

The generated digital models contain geometric data that allow for detailed and appearance elaboration in the same 3D design software that hosts the program or for exporting in different formats to various software, including environmental analysis, structural visualization, or BIM construction modeling programs. In these programs, additional information must be defined or added, and some geometric aspects may need to be modified or redone, especially curved surfaces that are not recognized or are misinterpreted. The ability to generate multiple volumes with different alternatives facilitates the study of possibilities by allowing similar adjustments to be made to different designs while maintaining certain conditions. For instance, adjustments in width for a larger printer or in length in response to the urban lot layout or interior distribution. Figure 6 shows some designs that can be elaborated from the output of the program.

3.4. Prototype Execution

The design selected for the prototype has a total length of 8.10 m and a width of 4.75 m, with the long sides featuring broad curves with a radius of 10 m and a regular height of 2.4 m. It includes three longitudinal areas: the living room-kitchen at one end and the bedroom at the other, with the entrance, hallway, and bathroom in the center. Most corners, including the central recess in the bathroom, have a rounded contour with radii of 60 cm. Each main room has three large windows, and there are two doors (entrance and bathroom).

In accordance with the seismic analysis, the structure consists of hollow walls with interior reinforcements forming reinforced columns every 80 cm in larger curved walls and 40 cm in smaller ones. The foundation includes a reinforced concrete lower tie of 20 × 30 cm and an upper tie of 20 × 20 cm, with metal lintels for connection. To meet the constraints imposed by the construction sequence breaks in the long walls are also established, including small, interspersed windows, resulting in seven wall sections.

The base is reinforced with a continuous 40 × 80 cm concrete foundation and a similar material floor over a compacted gravel base. The roof consists of a metal framework with a thickness of 1.2 mm, covered with wooden sheets on the interior ceiling and eaves, and pre-painted corrugated metal roofing, with a central channel and edges made of painted rolled steel sheets. Windows and doors have aluminum frames with glass and wooden leaves, respectively. Electrical and systems installation, as well as sanitary and kitchen equipment, are included.

Perimeter path planning for the walls was carried out, with interior segments to contain the columns and recesses for the upper tie. The walls were printed in sections in the laboratory, as the on-site execution was still experimental, with a printing speed of 50 mm/s and filaments with a cross-section of 4 × 1.5 cm (width × height). Each meter of wall height was completed in one hour on average, with walls including outer and inner filaments, an interior wavy filament, and transverse support bars. The seven wall sections were completed in approximately 29 h of printing, treated with moisture protectors, and transported to the site after a one-week curing period.

The on-site work began with tracing, excavation, installing foundation rebars, and pouring concrete, followed by connecting the foundation rebars to the column bars. Support templates and braces were required to accommodate the curvature of the elements. The walls were then installed with self-compacting concrete used to fill the columns, and expanded polyurethane was applied in the control joints between intermediate walls. Next, the lateral cladding and thermal insulation were completed. A lightweight metal roof structure was installed, featuring rainwater drainage toward the central axis. The walls were coated with epoxy paint mixed with crushed cork. Cement flooring was applied, and PVC-framed double-glazed windows and wooden doors were installed. Additionally, electrical and sanitary conduits, accessories, and fixtures were put in place, along with several printed exterior planters and pavements. Figure 7 shows some of the sequential steps followed in the fabrication and construction of the housing prototype.

4. Discussion

This work reviews the general geometric characteristics of houses in Chile and experimental 3D-printed houses worldwide to synthesize conditions programmed into a parametric shape generation system to enable the creation of various design solutions. One solution was selected and detailed for fabrication, including generating the toolpaths for the walls—the load-bearing structure—and fully developing the construction design, culminating in the execution of a housing prototype. This experience demonstrates the variety of solutions enabled by parametric design and the feasibility of using 3D printing to materialize them.

The diversity of generated shapes produces simple alternatives similar to those built with conventional construction systems and more complex ones that require detailed verification in their printed development. These complex designs may involve special reinforcements or additional tasks, such as inclined walls, pronounced curves, and projections. The execution can be developed with prefabricated parts printed off-site, transported and mounted in the place, or printed on-site according to the size and capacity of machinery for moving. They may also present challenges in integrating roofing elements, installations, openings, and furniture, which must be verified for their expressive or spatial contribution. Thus, the shape generation system should be complemented with adequate detailing and a smooth integration with construction modeling and planning to ensure feasibility and effectiveness. Particular attention should be given to completing roofs and openings to control their architectural development as well as to foundations and technical installations to guarantee adequate constructive execution. These efforts are framed by the conditions imposed by the printing material and equipment.

The roofs of 3D-printed houses can be lightweight structures made from various materials, often with protective eaves that add visual depth to the overall volume. Alternatively, flat slabs can be used, though these require additional reinforcement of the wall structure for support. The feasibility of 3D printing roofs, particularly in multi-story buildings, still demands further research and evaluation. For windows and doors, openings must be left in the walls, or the printing process must be interrupted to create these elements as separate sections. In some cases, maintaining lower parts like windowsills and upper parts such as lintels introduces complex structural challenges. Edges must also be finished to properly fit frames and secure seals. Electrical, plumbing, and climate control systems present another layer of complexity, as these installations either interrupt wall sections or need to be channeled through or over the printed walls. This requires careful coordination between design and execution. Consequently, integrating 3D-printed construction with other building processes remains a significant challenge. Additionally, regulatory adaptations are still needed to fully accommodate this form of construction.

The geometric arrangement of housing designs, based on characteristics prevalent in Chile and the possibilities of 3D-printed construction, demonstrates broad versatility and the feasibility of applying this technology for residential execution in the country and similar regions. It also supports the exploration of new forms that expand current architectural repertoires, primarily through curved shapes, introducing different aesthetic and functional possibilities.

Moreover, the systematization of the process, at least in the generation of volumes and the planning of toolpaths, offers a digital integration and analysis that challenges current workflows in professional settings and hierarchies. It highlights technical information management tasks by expanding decision-making possibilities, linking characteristics, blurring work levels and fields, and promoting development of multidisciplinary teams. It also heavily instrumentalizes tasks and decisions, dependent on specific software and hardware, with procedures and data.

For future research in the technical development of the generative design system, three objectives will be considered. First, the thickness and sections of walls, according to structural and thermal insulation requirements, should be defined based on local conditions. This would permit the direct generation of toolpaths for machinery control according to available materials and improve the articulation between design and construction. Second, the arrangement of openings, doors, windows, and interior partitions in each volume should be defined, considering the functional requirements of the layout. Third, the housing volumes should be clustered into urban units to explore possibilities for urban design.

Other development aspects may include enabling the selection of materials and appliances to expand design possibilities, improving visualization capabilities to support enhanced user participation, integrating structural and environmental analysis to gain a deeper understanding of design performance, and using optimization for better adaptation of designs to contextual conditions. Additionally, random generation under general parameters may be included to support more creative design explorations. Thus, the design system can be integrated into the promotion of 3D-printed housing for Chile and other countries, contributing to meeting the current growing housing demands and overcoming the challenges faced by the construction industry.

In summary, the executed prototype demonstrates the constructive feasibility and architectural potential of 3D printing technology for residential development in Chile and equivalent areas. However, it also unveils possible challenges due to current execution difficulties under experimental conditions and the availability and development of supplies, equipment, and personnel. Moreover, integrating conventional elements and organizations in residential construction and their commercial and social projections poses challenges. Nevertheless, these challenges seem addressable with the progressive application of technology and the overall evolution of the construction industry and social interests.