Interdisciplinary Drivers of Puerto Rico’s Informal Housing Cycle: A Review of Key Factors

Abstract

In many disaster-prone regions, lower-income communities face disproportionate impacts due to the prevalence of informal housing. Informal housing, characterized by substandard construction and lack of adherence to building codes, exacerbates vulnerabilities during disasters, leading to widespread destruction and hampered recovery efforts. This study examines the multifaceted causes of informal housing in Puerto Rico using a qualitative content analysis of applicable literature. Seven interdisciplinary factors were derived from 42 relevant manuscripts with identifiable factors linked to informal housing in Puerto Rico: Knowledge, Perception, Government Dynamics, Institutional Support, Enforcement, Culture, and Resources. Despite post-disaster efforts advocating for building back better, systemic challenges perpetuate informal housing practices, reinforcing cycles of vulnerability. This research underscores the need for integrated decision making in pre-disaster preparation and post-disaster reconstruction efforts. This research presents a detailed understanding of the Informal Housing Cycle, demonstrates how interdisciplinary factors are barriers to safe and sustainable housing, and explores the complex relationships between these factors. This study aims to guide policy and practice to reduce future disaster impacts on Puerto Rico housing, thus breaking the cycle of vulnerability, empowering communities, and fostering sustainable resilience in post-disaster reconstruction efforts.

1. Introduction

In disaster-prone areas, lower-income households face disproportionate impacts [1], largely due to the prevalence of informal housing—dwellings built without adherence to codes and standards, often with inadequate materials and limited resources and without permits or secure land ownership [2]. Informal housing often arises on marginal or high-risk land—such as steep hillsides, flood-prone coastal zones, and peri-urban fringes—where tenure is insecure and access to infrastructure and services is limited [3]. These spatial patterns mirror those seen across Puerto Rico’s coastal plains and interior mountains, where hazard exposure and settlement informality frequently overlap [3]. Poverty is a central driver of informal housing, as households lacking sufficient income are unable to access formal markets, secure land tenure, or afford compliant construction materials and labor [1]. Informal housing units are particularly vulnerable to natural hazards and are often severely damaged or destroyed during hazard events. When hazard impacts overwhelm communities, they become disasters due to widespread catastrophic damage to the built environment and associated loss of life [4]. Unfortunately, without the means to build back better, reconstruction often defaults to the same informal methods [5].

The conventional recovery approach follows a pattern of immediate humanitarian response, then post-disaster needs assessments that guide recovery and reconstruction [6]. The central challenge is balancing short-term support for basic needs (e.g., health, safety, security) with long-term rebuilding of housing and infrastructure [7]. In recent decades, the concept of building back better has emphasized large-scale reconstruction as an opportunity to improve communities. For housing specifically, this has meant improving construction practices and ensuring compliance with building standards [8]. However, an overly narrow focus on technical improvements can overlook the deeper systemic issues that perpetuate informality, including limited education, cultural norms, and weak institutional support [9,10]. As a result, residents with limited financial resources often continue to build informally, while those lacking homeownership documents frequently receive little or no rebuilding assistance [11]. Consequently, the most economically disadvantaged populations are left to reconstruct with minimal support [12].

Although informal housing in Puerto Rico has been widely studied, prior research tends to focus on isolated aspects such as engineering failures or aid eligibility, with little attention to the full set of interrelated drivers. To address this gap, this study used a qualitative content analysis of the existing literature [13,14] to identify and examine the interrelated factors driving informal housing in Puerto Rico. This research aimed to better understand the role of informal housing in disaster recovery and how rebuilding efforts could be improved to support disadvantaged populations. Resolving the repetitious nature of informal housing practices is a multidisciplinary challenge [15]. For example, education programs play a crucial role in promoting awareness of building codes and safer construction practices [16]. Economic initiatives empower residents to access resources needed for formal housing solutions. Moreover, understanding cultural considerations can help tailor interventions that resonate with communities. Puerto Rico serves as an instructive case study due to its governance structure, demographics, and frequent exposure to natural hazards. By examining informal housing in Puerto Rico’s recent post-disaster reconstruction, this study aims to inform more effective housing practices that reduce vulnerability and strengthen community resilience.

2. Background

Informal housing exists globally, varying from easily identifiable structures to those whose informality can only be identified through conversations with owners or reviewing construction documentation [10]. Definitions of informal housing vary and are often ambiguous [17], but typically encompass substandard housing and/or ownership issues [18]. The Government of Puerto Rico defines informal housing as a home built with “self-managed construction that does not use an architect or engineer, permits, or the relevant codes, and often happens on land for which the residents do not own the proper title” [1,19]. In short, informal housing generally refers to housing that fails to comply with established design and construction rules, often including an aspect of non-enforcement [2]. Informality highlights the idea that institutions define legality and often fail to address urban poverty and inequality. This creates a nuanced distinction between informality and illegality, contrasting an ‘absence of rules’ with a ‘violation of rules’ [20]. Nonetheless, urban planners and policymakers often overlook informal settlements, denying their existence because they are seen as incompatible with globalization [21]. Many researchers agree that an integrated, holistic approach is needed to understand the complex, heterogenous, and hybrid nature of informality [15]. However, this complexity must be understood to find effective comprehensive solutions to informality.

Puerto Rico illustrates these broader dynamics of informality, with its unique political and economic circumstances shaping housing development patterns on the island. As a U.S. territory, Puerto Rico lacks full political representation and has historically faced uneven policy enforcement, including inconsistent application of building codes [22,23,24]. This governance gap has contributed to extremely high rates of informally built homes [25], which are especially vulnerable to damage when hazard events occur [26]. Available evidence suggests that informal construction is especially concentrated in low-income coastal municipalities and rural interior regions, where enforcement and infrastructure access are weakest [3]. Some estimates indicate that informal housing might account for up to half of the island’s housing, varying between 260,000–700,000 informally built homes [10,27,28]. One reason for this is much of the housing stock is built on land which family members have informally subdivided over generations without any official land title [9]. There are an estimated 260,000 homes in Puerto Rico without titles or deeds [29]. Informal housing in Puerto Rico is also affected by the extreme poverty level. The overall median household income in Puerto Rico is less than one-third of the U.S. median income [27], with about 45% of Puerto Rico residents living below the federal poverty level [29]. A general lack of affordable housing has led to residents building their own homes [30].

Informal construction practices are particularly vulnerable in the face of natural hazards [31,32]. Puerto Rico is especially susceptible to hurricanes and earthquakes. Most recently in 2017, Hurricanes Irma and Maria, category five and four storms, respectively [33,34], devastated the island. Hurricane-force winds, storm surge, and intense rainfall caused nearly $90 billion in damage [35], and led to an estimated 300,000–400,000 homes needing reconstruction or repair [1,10]. Following the hurricanes, over 1.1 million households applied for federal assistance. However, the rebuilding process was complicated and slow, and even five years after the hurricanes, much of the housing reconstruction remained incomplete [16,24,36]. This led many residents to repair or rebuild their homes themselves [37]. Even though 90% of Puerto Rico homeowners filed applications for immediate relief and housing assistance from the U.S. Federal Emergency Management Agency (FEMA), individual assistance was granted to only 40% of the applicants [27,38]. Unfortunately, while still recovering from the hurricanes, the island was hit by several earthquakes in early 2020, including two at magnitudes 6.4 and 5.8, respectively [39]. The resulting earthquake damage, in turn, restarted the housing recovery process for many [40,41]. These consecutive, multi-hazard events caused extensive damage to residential structures across Puerto Rico, continuing to make recovery challenging for residents.

Following the 2017 hurricanes, research on Puerto Rico’s informal housing expanded, with topics generally clustered into five categories. The first area explored how pre-existing poor socioeconomic conditions pushed many households into informal self-reconstruction, accelerating recovery for some but entrenching safety and legal risks for others [10,42]. The second area, reconstruction efforts associated with social capital, determined that neighborhood networks, mutual aid, and informal labor have in many instances replaced scarce formal assistance and shaped who has rebuilt, and the methods and pace associated with the reconstruction [1,43]. Third, engineering assessments of common informal typologies have identified key recurrent failure modes (e.g., weak roof-to-wall connections) and have proposed low-cost retrofits and detailing (e.g., straps, improved anchorage) to materially reduce wind damage [44,45]. Fourth, policy analyses have documented high FEMA ineligibility rates, often tied to ownership proof, discussing how documentation rules excluded many informal housing occupants [11,46]. Finally, work on tenure regularization and using community land trusts suggests that securing land rights can lower flood risk and reduce displacement, especially when residents participate in planning processes [47,48,49]. Despite this body of research, no study has yet systematically examined the full set of drivers of informality in Puerto Rico and their interrelationships.

More recent policy evaluations and field studies highlight how Puerto Rico’s housing recovery continues to be shaped by informality and uneven institutional capacity. Recently FEMA has expanded acceptable documentation for homeowners without formal land titles, introducing sworn declarations and other flexible measures tailored to Puerto Rico’s context [50]. Federal oversight, however, indicates that recovery programs still face delays and implementation risks, with the U.S. Government Accountability Office (GAO) noting that progress has been made but challenges remain in delivering housing assistance equitably [51]. Complementing these evaluations, an updated community development block grant/disaster recovery action plan from the Puerto Rico Department of Housing details how allocations from mitigation and disaster recovery funds are being deployed for rebuilding homes and economic revitalization [52]. While many initiatives are underway, progress in rehabilitation and housing production has not yet matched some targets, and significant unmet needs remain due to funding constraints, administrative capacity, and scale of damage. At the community level, recent empirical studies underscore how informality shapes recovery: survey research in Loíza and Yabucoa links unemployment and lack of ownership documents to persistent self-reconstruction practices [10], while new engineering analyses assess low-cost retrofits to strengthen informal housing against hurricane winds [53]. Together, these policy updates and empirical findings show that while incremental reforms have addressed some documentation and program design issues, the systematic barriers driving informal housing in Puerto Rico remain deeply entrenched.

In summary, informal housing in Puerto Rico has experienced disproportionate damage during hazard events due to poor construction quality and limited resources. Since the 2017 hurricanes, research has examined socioeconomic conditions, social capital, engineering vulnerabilities, policy barriers, and tenure solutions, but no study has yet addressed the full set of drivers or their interrelationships. More recent policy updates and field studies indicate incremental progress but also highlight persistent institutional weaknesses and continued reliance on informal practices. While deficiencies in construction are well recognized, the collective and interconnected nature of the factors sustaining informality remains poorly understood. This research was initiated to identify and analyze these factors and their interrelationships in order to explain the persistence of informal housing practices in Puerto Rico.

3. Methods

This research used a two part-approach: (1) a systematic literature review guided by the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) protocol [54,55] for identifying relevant literature, and (2) a qualitative content analysis approach (similar to grounded theory analysis) for deriving the appropriate factors and analyzing their interconnected relationships [14,56]. These two complementary methods provide a robust research approach for comprehensively and methodically gathering, assessing, and synthesizing information from existing research relevant to a particular research question [57]. This coupled approach is commonly used to develop a broader perspective of a given research topic and identify gaps in understanding [14,58]. The intention of this research was not to develop a comprehensive literature summary of housing in Puerto Rico, but rather to develop a thorough understanding of the factors influencing informal housing, drawing from a broad sampling of related literature. Consequently, significant emphasis was placed on the qualitative content analysis aspect of the research. Figure 1 shows the five key steps that were used in this research approach.

The first step in this research approach was to define the appropriate research questions (Figure 1). The purpose of the project was to identify and explore interdisciplinary factors related to informal housing in Puerto Rico through a built environment lens. Thus, the research questions for this project included:

• What factors contribute to informal housing in Puerto Rico?
• How do informal housing factors relate to each other?

The next steps in the research approach included (step 2) selecting appropriate databases for finding literature and applying key search terms and (step 3) applying inclusion and exclusion criteria to identify relevant documents for further analysis (Figure 1). Several research principles were followed to ensure validity of the data including diversity of source information, quality and relevance of the literature selected, and research saturation [55]. Although PRISMA does not prescribe how to conduct a systematic review, PRISMA guidelines recommend transparent and complete reporting of systematic review processes used for identifying relevant literature [54]. Three academic databases were used for finding literature, including Scopus, the ASCE Library, and Google Scholar. Key search terms focused on narrowing the literature to studies focused explicitly on Informal Housing in Puerto Rico. The search terms Disaster and Construction were also used in combination to help focus the list of potential literature on research that would include sufficient description of factors associated with informal housing in Puerto Rico. All four terms were selected because collectively they define the context for the research problem. Although informal housing is common in Puerto Rico, it is not generally associated with being problematic in the literature except in the context of disaster reconstruction. Thus, the intersection of these four search terms served as the basis for identifying literature relevant for this study.

PRISMA guidelines further suggest that authors report search strategies and results [54]. Figure 2 shows a more detailed flowchart of the processes associated with identification, screening, and determining eligibility, along with the appropriate inclusion and exclusion logic used during the literature search [54]. Following the comprehensive database searches, manuscript titles and abstracts were reviewed to determine relevance. A significant number of manuscripts were eliminated during this step, simply because the identified research did not have sufficient connection with Puerto Rico housing. Manuscripts were further checked for explicit connection to informal housing and one final time for sufficient contextual information regarding identifiable informal housing related factors. Although much of the final dataset was rooted in the built environment, we specifically sought to ensure that a broader set of interdisciplinary informal housing related impacts, including cultural and socioeconomic factors, were included, as appropriate. This review process generated 42 relevant documents (as shown in Figure 2), composed of peer-reviewed journal articles and conference papers, academic dissertations, and government reports. This approach (Figure 1) was followed to ensure that the resulting documents provided a valid comprehensive unbiased dataset for further analysis.

The research team used a systematic process known as qualitative content analysis to review the documents in the dataset (Figure 1, step 4), where individual results were reviewed by the team to identify and remove subjective inconsistencies and validate findings [59,60,61]. Qualitative content analysis is a systematic method for interpreting textual data by identifying, coding, and categorizing patterns and themes [62]. A coding protocol was established to aid researchers in systematically reviewing the data. First, two researchers manually conducted open coding across the data, identifying unique and relevant concepts and research questions [63,64]. Next, the researchers participated in focused coding exercises to develop key categories of concepts. This resulted in the following codes: barriers, FEMA, further research, housing stats, informal housing, informing/communication, multi-level involvement, overview, perception, post-disaster and pre-disaster issues, relocation, social capital, socioeconomic vulnerabilities, and solutions. The coding protocol was then applied to each document in the dataset and produced unique ideas and key findings. Coding, in this context, refers to the process of labeling excerpts of text with short phrases that capture their meaning, allowing for systematic organization and interpretation of the data [62]. As is common in qualitative research, the coding process proceeded in an iterative fashion to ensure complete coverage of all important information. Qualitative data analysis software was used to manage the data extraction processes and content analysis portions of the project. During the content analysis phase of the research, coded excerpts were linked to each other, and themes, patterns, and relationships were specifically identified [65]. This was done through the development of network maps, further organizing individual ideas. A summary was then created for each coded category. Finally, the data was thoroughly reviewed by the research team to eliminate bias and ensure validity and then synthesized to provide a comprehensive summary of the findings (Figure 1, step 5).

4. Results

This study identified seven interrelated factors that shape informal housing in Puerto Rico. The following sections summarize each factor, its context, and key insights from the literature. These seven factors include:

• Knowledge: lack of formal training and effective communication
• Perception: distrust in government, hazard misperceptions, and low self-efficacy
• Government Dynamics: power and place mismatch between Puerto Rico and U.S.
• Institutional Support: Poor resource allocation, weak communication, and disorganized recovery
• Enforcement: Inconsistent code enforcement and complex permitting processes
• Culture: Norms of self-building, inheritance practices, and resistance to relocation
• Resources: limited finances, materials, insurance, and legal tenure

4.1. Knowledge

Knowledge gaps among residents and builders limit safe construction practices and complicate recovery efforts. Access to reliable information is crucial for making effective and responsible construction decisions. In Puerto Rico, however, many construction workers lack formal training and often learn by trial and error, leading to misunderstandings about safety measures [66,67,68,69]. Even when workers recognize potential hazards, they are generally unaware of proper mitigation strategies [53]. Research shows that limited technical capacity, more than financial constraints, is the primary driver for unsafe housing practices [16,43]. Formal technical guidance can be difficult to access, with communication typically one-way—from government agencies downward—leaving residents uncertain about where to obtain reliable support [9,66]. As a result, people often turn to hardware stores, relatives, or social media instead of engineers or municipal offices [43,44]. This contributes to highly variable housing quality, as individuals build to the best of their ability while managing tradeoffs [44]. Moreover, many informal homes are located in physically unsafe areas, such as steep slopes or unstable soils, whose risk is poorly understood [25,70], particularly in hillside and flood-plain communities where hazard exposure is spatially clustered [3].

Even when residents are aware of hazards and mitigation options, decisions may still be constrained by household dynamics, financial limitations, or community values [69]. At the same time, outside decision makers often underestimate local networks, practices, and resources, viewing them as less capable, while lacking knowledge of local vulnerabilities. This disconnect contributes to unequal resource distribution and unresolved risks [71]. Improved two-way communication is therefore essential. U.S. assistance is allocated to Puerto Rico, but without mechanisms for residents to share local context and needs, programs remain less effective [24]. Establishing clear communication systems—supported by translation services and contingency plans for disrupted infrastructure—is critical, and these must be in place before disasters occur [72].

4.2. Perceptions

Community perceptions of risk, safety, and trust in government strongly influence housing decisions and recovery choices. When hazards are perceived as unimportant or uncontrollable, individuals are unlikely to mitigate risks [69]. Perceptions of safety often fluctuate depending on the most recent hazard event occurred and the destruction witnessed, creating barriers to effective action. For example, one study found that the residents overestimated the costs of recommended safety measures and thus avoided them [9]. Preconceived notions of what constitutes safe construction also shape which solutions are considered viable. In Puerto Rico, long-standing beliefs within the construction industry have limited acceptance of newer, safer methods [9]. Exposure to multiple hazards further complicates perceptions, with people prioritizing protection against the most recent event while neglecting less frequent threats such as earthquakes [43,66]. As a result, vulnerability to future hazards often increases. While most residents demonstrated limited awareness of seismic safety, those with prior construction experience displayed broader understanding and a more proactive outlook [43].

Hazard events can both strengthen and weaken trust in formal construction processes. After disasters, many residents expressed greater willingness to rely on professional engineers and architects, recognizing the value of oversight to prevent shortcuts [66]. Yet the failure of many formally constructed buildings—particularly schools—during earthquakes severely undermined trust in government and official certifications [66,68]. Public frustration grew when only 20% of schools reopened weeks later, reinforcing doubts about institutional competence. More broadly, experiences of ineffective communication, delayed assistance, and even forced displacement for economic and tourism purposes deepened distrust in FEMA and local authorities [24,71]. At the same time, residents acknowledged the government’s necessary role in recovery, highlighting the importance of improving public perception and enabling community participation in decision-making [72,73]. Effective disaster communication is central; mismatched expectations after the hurricanes left residents angry and disillusioned, wanting not only aid but a return to comfort, stability, and control over daily life [74]. Recovery thus reflects a continuum between displacement and restoration, as households negotiate what “home” means in the aftermath of disaster [75].

4.3. Government Dynamics

Puerto Rico’s territorial status and ambiguous relationship with the U.S. government create systemic governance challenges for housing recovery. These dynamics become especially visible after disasters, when federal and local responsibilities overlap [1,24]. Though Puerto Rico ceased to be a colony in a formal sense when it became a U.S. territory in 1917, the legacy of colonialism persists in the island’s governance structures and its perception as “other” [22,24]. Like typical colonial arrangements, regulations are imposed from afar without sufficient regard for local culture, norms, or needs [24,76,77,78]. As an unincorporated territory, Puerto Rico lacks representation in Congress and the Electoral College, limiting its ability to advocate for itself in times of crisis [23]. Yet federal agencies such as FEMA and the U.S. Department of Housing and Urban Development (HUD) dictate disaster aid and reconstruction policy, creating a mismatch of place and power that has led to delays, miscommunication, and slower recovery compared to mainland states [9,23,24,79,80]. For example, Puerto Rico received significantly less FEMA aid in the first two months after Hurricane Maria than U.S. states hit by Hurricane Irma [23,24,80].

This power imbalance constrains contextually appropriate housing reconstruction. Federal regulations often override local expertise, sidelining qualified Puerto Rican actors from best equipped to design sustainable, culturally informed solutions [24,79]. Policies like the Merchant Marine Act, which restricts imports to U.S.-flagged ships, have increased material costs and exacerbated resource scarcity [24,80,81,82]. Similarly, FEMA’s requirement that residents present land title or proof of homeownership to access aid excluded many Puerto Ricans, as formal documentation is uncommon [24,83,84]. These policies, shaped by distinct decision makers, illustrate how neocolonial dynamics undermine local recovery capacity, reinforce dependence on federal aid, and contribute to the persistence of informal construction [85,86,87].

4.4. Institutional Support

Institutional capacity and support mechanisms in Puerto Rico are often inadequate, leaving many households without sufficient assistance after disasters. For example, the reimbursement system required contractors to complete work before payment, forcing small firms to cut corners to stay competitive with larger outside companies [81,88]. Even after five years of rebuilding, many homes remained unfinished, with residents still living under damaged roofs [24,43]. Aid distribution was uneven; some municipalities received little assistance because they were classified as flood zones, while “squatter communities” were excluded altogether, despite urgent needs for clean water and medical support [70,84]. These gaps pushed many residents toward informal construction.

Government assistance programs were plagued by barriers that prevented households from accessing support. Up to 60% of FEMA applications were denied, often with unclear rejection letters [27,43]. Language barriers, complex online applications, and proof of ownership requirements created further obstacles, particularly since internet access and formal documentation were limited [10,24,86,87,89]. Puerto Rico’s inconsistent address system compounded the problem [11]. Even approved aid was frequently insufficient, and some recipients faced accusations of fraud when funds were misused [10,11,84]. Assistance inspections posed another hurdle; cutoffs for damage eligibility reflected U.S. standards rather than Puerto Rico’s context, leaving many poor households excluded. Inspections were missed due to scheduling issues, lack of rescheduling options, and inspectors who often only spoke English had limited training and were incentive to minimize time spent on assessments [11,42].

These policies, designed without consideration for local context, slowed reconstruction, increased costs, and led some homeowners to abandon rebuilding. The physical and political distance between Puerto Rico and the mainland U.S. reduced federal awareness of urgent needs and delayed problem solving [24]. Local nongovernmental organizations (NGOs) and advocacy groups, although better positioned to address community challenges, were often excluded or lacked the resources to scale their efforts [24,90]. At the community level, aid distribution was sporadic and poorly coordinated; some supply locations were announced only hours in advance, public services took months to restore, and food and water aid ceased after just seven months despite ongoing needs [74,75]. These deficiencies underscored the importance of contingency planning to ensure resources and services are available for vulnerable populations who cannot recover on their own [1].

4.5. Enforcement

Weak and inconsistent enforcement of building codes perpetuates unsafe housing practices across Puerto Rico. Although construction standards are generally equivalent to those in the mainland U.S., enforcement is especially limited in the residential housing sector. Informal builders often lack technical training, and without inspection or oversight, unsafe, construction practices persist [25,43]. Disasters present opportunities to strengthen codes and improve the built environment [66], but when minimum standards go unenforced, updates rarely influence most of the housing stock. This gap is particularly acute in residential construction, where changes fail to address limited worker training, lack of inspections, and weak implementation requirements [25].

The permitting process itself discourages formal construction. Acquiring building permits requires over 18 approvals and can take over a month [42]. Paperwork is complex, guidance is scattered, and households with lower education levels face particular difficulty navigating the system [10,11]. Even after obtaining permits, inspections are not mandated or systematically enforced, and those who seek them must pay out of pocket for third-party services [66]. With too few inspectors to oversee compliance, large numbers of unpermitted structures continue to proliferate [42]. These bureaucratic barriers make informal construction both faster and cheaper, even though it produces unsafe housing [40,67].

Effective code enforcement requires government support combined with community engagement and education. Raising awareness of the benefits of compliance, reducing the time and cost of permitting, and imposing meaningful penalties for noncompliance would help disincentivize informal practices [42]. Involving local stakeholders in policy design and implementation would also ensure that solutions reflect local realities and encourage legitimacy [21]. However, enforcement of reconstruction regulations has been inconsistent, with fragmented oversight between governing bodies [24]. Following Hurricane Maria, mismatched local and federal housing policies hindered rebuilding, sustained informality, and further eroded public trust [24]. These failures disproportionately harm vulnerable populations, who face limited resources and reduced regulatory protection after disasters [1,9,10,67,68].

4.6. Culture

Longstanding cultural norms, such as self-building and multigenerational inheritance, reinforce the persistence of informal housing in Puerto Rico. Informal practices like adding a second story or building without reference to codes have become normalized [10,83]. This cultural acceptance stems from weak enforcement, low demand for formal planning, historical housing policies, and prohibitive costs of formal construction [10]. While these practices provide short-term flexibility, they create long-term challenges, especially when residents seek federal disaster aid that requires proof of compliance. Over time, these informal practices have become deeply ingrained, blurring the line between cultural tradition and systemic vulnerability.

Strong community bonds also shape housing decisions. Multigenerational households and patterns of inheritance foster deep social capital within neighborhoods, making departure from such communities difficult [71,73,91]. These social and cultural dynamics are often tied to specific places—family land parcels and long-established neighborhoods—reinforcing attachment to location even in hazard-exposed areas. After disasters, residents in disadvantaged areas are often offered relocation assistance because rebuilding informal homes is not permitted. Yet many refuse relocation, prioritizing cultural and social ties over improved housing options, and instead return to informal reconstruction [24]. Even when living conditions were substandard, residents preferred to remain with family and neighbors, reflecting Puerto Rico’s strong community orientation [70,92]. These dynamics highlight how culturally rooted practices and overlooked community priorities complicate policy-driven relocation and housing recovery efforts [24].

4.7. Resources

Limited financial, material, and legal resources constrain households’ ability to pursue formal construction and recovery pathways. Studies show that households headed by women, the elderly, the uneducated, and the unemployed are strongly correlated with informal housing [10,83,91]. These demographics are often low-income (less than $10,000 per year) and face greater barriers to formal homebuilding [9,93]. High real estate costs and population growth further push owners to construct informal additions [94]. Powerlessness, bureaucratic barriers, and limited financial means reinforce reliance on informal processes [69]. Local income inequality also compounds the problem; higher income households raise housing and insurance costs, pricing formal housing out of reach for low-income families [95,96].

Land tenure and homeownership issues are also critical. Many residents cannot provide land titles because their homes were inherited, a common cultural practice tied to multigenerational living [10,11,23,44]. This, combined with factors such as limited mobility, health challenges, scarce materials, unemployment, poor access to public services, lack of construction knowledge, and minimal internet access, makes formal construction less feasible [1,24,71,74,97,98]. While some households build informally out of necessity, other do so for flexibility in construction timelines [10] or even by choice, as seen in second homes or additional floors built by upper-class families [71,99]. Today, estimates suggest that roughly half of Puerto Rico’s houses incorporate some form of informal construction [1,27].

Formalizing these dwellings through titling would be costly and create new risks for residents [100]. Recovery efforts are further hampered by unresolved inheritances, duplicate applications, non-standardized addresses, unsuitable housing locations, and challenges with inspections and use of recovery funds [11,23]. For low-income households, these delays extend homelessness and increase reliance on informal rebuilding [16,23]. In disadvantaged communities, social capital provides critical support during reconstruction, but limited resources often leave homes unfinished or unsafe [1,71].

4.8. Summary of Findings

In summary, this research revealed seven interrelated factors that collectively sustain informal housing practices in Puerto Rico. These factors present distinct but overlapping challenges, ranging from technical knowledge gaps and limited resources to entrenched cultural norms and systemic governance issues. Importantly, these barriers do not operate in isolation; rather, they interact in ways that reinforce informality, demonstrating the need for integrated, multi-level solutions instead of piecemeal reform. The literature highlights several potential pathways for progress, including expanded education and training, more participatory and culturally sensitive approaches, streamlined institutional processes, and stronger enforcement of existing standards.

Table 1. Factors, findings, and potential solutions for safe and sustainable housing in Puerto Rico.

Factor	Findings	Potential Solutions
Knowledge	Limited construction training; reliance on informal guidance; weak two-way communication	Expand technical training programs; establish multilingual, two-way communication; provide accessible technical guidance
Perceptions	Risk perceptions shaped by recent events; distrust in government; limited awareness of multi-hazard risks	Provide multi-hazard education; promote participatory recovery planning; showcase safe housing models
Government Dynamics	Colonial power mismatch; lack of representation; federal policies exclude residents and raise costs	Adapt aid requirements to local realities; strengthen local governance capacity; engage NGOs and community actors in decision-making
Institutional Support	High aid denial rates; language and digital access barriers; inadequate inspections; uneven aid distribution	Simplify and translate applications; enable offline/low-tech processes; train and monitor inspectors; expand municipal and NGO capacity
Enforcement	Codes exist but enforcement is inconsistent; permitting is lengthy and costly; inspections are limited	Streamline permitting; reduce compliance costs; mandate and expand inspections; raise public awareness of compliance benefits
Culture	Informal construction normalized; inheritance and multigenerational living limit land titling; relocation resisted	Support in situ upgrading; develop community land trusts; design culturally sensitive safety programs
Resources	Poverty, unemployment, and inequality limit access to housing finance, insurance, and materials; land tenure and inheritance issues block formality	Expand affordable housing finance and microloans; provide insurance subsidies; pursue safeguarded land tenure programs; improve resource access

summarizes each factor alongside key findings and corresponding solutions identified in the reviewed studies, providing a holistic view of both the drivers of informal housing in Puerto Rico and the opportunities to disrupt them.

5. Discussion

5.1. Informal Housing Cycle

This research has identified seven factors that influence informal housing in Puerto Rico and include a broad range of disciplines beyond the built environment. As demonstrated, these factors are individually complex yet interrelated. The next part of the analysis was to explore the connections between these factors. Paradoxically, these factors encourage informal housing, before and after natural disasters occur. The presence of these factors results in an Informal Housing Cycle where residents build informally, natural disasters break these houses down, and residents build informally again [1]. This cycle is extremely unsustainable and detrimental to the residents and economy of Puerto Rico. The Informal Housing Cycle is shown in Figure 3, with five unique stages that demonstrate the circularity of informal housing processes.

The Informal Housing Cycle begins when residents choose to build informally (stage 1—Housing Choice). This commonly occurs because of long-standing cultural practices, perceptions of safe housing, or because of financial limitations. Admittedly, residents may not feel they have a choice, but nonetheless informal construction process decisions lead to structures that are highly susceptible to negative effects from natural disasters [16]. Housing logic is complicated and individually unique, and residents’ decisions are influenced by affordability, accessibility, adequacy, and aptness [101]. The historical culture of informal housing is a significant factor that drives its prevalence.

The second stage is Lack of Enforcement of building codes and obtaining proper land titles and building permits. Lack of enforcement is typically associated with the plan review and inspection stages of design and construction and results from two overlapping challenges. First, Puerto Rico has lagged the formal processes of title and code compliance processes of the U.S. mainland. The building permit process in Puerto Rico is costly, time-consuming, and mostly privatized. Despite efforts to streamline the permitting process, Puerto Rico recently ranked 131 out of 190 countries, compared with a U.S. ranking of 39, in “Dealing with Construction Permits” ranking in the World Bank’s Doing Business report [42]. Land titling programs often fall short of achieving their social and economic goals, sometimes resulting in negative impacts for residents in areas without prior titling, while also placing significant demands on land administration agencies [100]. Yet, there remains significant pressure to become more formal in these processes. Second, significant resources are necessary to enforce building design and construction. This would require a complete transformation of the entire system, requiring financial backing, increased manpower, and especially time. The strong inertia of existing building processes, shaped by cultural background, would need to be overcome to effectively change how formal processes operate in Puerto Rico.

In stage three (Disaster Effects), vulnerable houses are either damaged or destroyed during natural disasters and require reconstruction. These effects are self-evident due to Puerto Rico’s susceptibility to both hurricanes and earthquakes. The recent hurricanes in 2017 and earthquakes in 2020 led to the damage and destruction of hundreds of thousands of homes on the island, devastating housing stock and leaving the residents in need of recovery support.

In stage four (Denied Support), residents with informal housing are commonly denied aid from institutions and federal agencies and typically do not have sufficient financial means to properly rebuild. This is a paradox, as those whose homes tend to experience the most damage (i.e., informal housing) are denied rebuilding assistance. For reconstruction efforts to be sustainable, support for those in need must include material replacement and further education and assistance [16]. This in turn, would provide residents with the ability to build back better, with stronger houses able to withstand future hazard events. Housing reconstruction is most successful when it is combined with improvements in community infrastructure, services, and opportunities to create real livelihoods [102].

Finally, in stage five (Decreased Trust), residents are left with lower trust in institutions because of inadequate assistance, proper resources, miscommunication, and knowledge to build safe housing. When residents’ expectations for post-disaster support are unmet, trust in the institution is eroded. Residents often resort back to informal construction, thus restarting the cycle. Trust is essential within communities, and trust-building must be incorporated within the very culture and across interactions. Increasing communication from the institution and increasing understanding of residents’ needs would likely increase trust between the two parties. Historical distrust would also need to be addressed for residents to overcome these perceptions [103]. Housing reconstruction is most successful when users are involved in design and construction processes [102], but this relationship needs to be strengthened in the case of Puerto Rico.

5.2. Barriers to Safe and Sustainable Housing

The Informal Housing Cycle demonstrates that the challenges of informal housing in Puerto Rico extend far beyond the lens of the built environment. It is the result of a complex web of social, cultural, and political factors that collectively perpetuate informal housing. Social dynamics, such as poverty and inequality, drive individuals to seek alternative housing solutions outside formal systems. Cultural factors, including long-standing traditions and community networks, shape the ways in which people adapt and respond to housing shortages. Political influences, such as inadequate policy frameworks and governance issues, further exacerbate the problem by failing to address the root causes effectively. Consequently, the Informal Housing Cycle is an interdisciplinary issue that demands a multifaceted approach, involving collaboration across various sectors and disciplines to find sustainable and comprehensive solutions.

The literature review revealed seven distinct factors that influence informal housing and are in fact barriers to safe and sustainable housing in Puerto Rico. Each barrier perpetuates the Informal Housing Cycle at various stages and compounds the effects of one another, further entrenching residents within the cycle. Because these barriers are interconnected, positively addressing one may have a positive influence on another.

Table 2. Directional cross-matrix of factor pairs.

Driving Factor	Dependent Factor
	Knowledge	Perceptions	Government Dynamics	Institutional Support	Enforcement	Culture	Resources
Knowledge		Limited construction knowledge skews safety perceptions	-	Incomplete understanding of local needs results in insufficient support	-	Limited construction knowledge contributes to culture of informal and unsafe housing	Greater knowledge unlocks further resources, including social capital
Perceptions	Perceptions affect what sources people believe to be reliable		Perception of P.R. as “other” allows U.S. to maintain current colonial dynamic	-	-	Fluctuating perceptions of informal housing influences strength of the historical culture	Perceptions of legal resources (i.e., permits, land titles) affect acquisition
Government Dynamics	Ineffective communication leads to delays in decision making	U.S. and P.R. dynamic promotes a perception of P.R. residents as “other”		Federal aid requirements are incompatible with P.R.’s capabilities	Place and power mismatch between the U.S. and P.R. hinders consistent enforcement	Federal dependencies slow progress from informal housing processes	Federal restrictions on P.R. ports cause scarcity and price increases
Institutional Support	Available support is not well advertised by providers	When support is misaligned with resident expectations, distrust grows	-		Lack of local government programs and resources prevents adequate enforcement	-	Many residents rely on institutional support for resources, especially during recovery
Enforcement	-	Lack of enforcement skews perceptions on necessity of permits and code compliance	-	-		Historical lack of enforcement strengthens the culture of informality	Lack of enforcement allows residents to neglect legal resources (i.e., permits)
Culture	A culture of self-building prevents learning proper construction practices	Longstanding cultural practices contribute to informal housing perceptions	Historical colonial relationship promotes federal dependencies	Informal housing culture is allowed by P.R. government institutions	Culture of informal housing slows adoption of building code enforcement		Poverty in informal housing culture prevents resource acquisition
Resources	Resources (i.e., finances, social capital) supports knowledge acquisition	-	-	Legal resources (land titles, insurance) drive post-disaster support received	-	Lack of resource availability/access perpetuates informal construction

Shading represents mutually reinforcing relationships.

shows the directional relationship between pairs of barriers derived from the data. These results are presented in a cross-matrix format with rows representing ‘driving factors,’ and columns representing ‘dependent factors.’ The network descriptions shown in the table are not intended to be comprehensive but do show important connections that exist. Ultimately, this shows how the presence of one barrier may affect the presence and impact of another. Figure 4 visually illustrates these same directional relationships in a network graph. Each barrier is represented as a node in the figure, with connections showing either a one-way or two-way directional relationship. Node size is scaled according to a measure of relative importance (eigenvector centrality) [104]. For this discussion, the position of nodes in this network graph has no meaning.

In our analysis of relationships between these barriers, we found connections can either be one or two-way. A one-way relationship exists where one barrier generally imposes an effect on another, but no immediate evidence exists of an effect between the two barriers in the other direction. For instance, a one-way relationship appears between Institutional Support and Perceptions (see Table 2), where the degree of institutional support was shown to affect resident perceptions. However, there was little evidence that resident perceptions affected the degree of institutional support. An example of this specific one-way relationship was evident in post-disaster interviews where residents stated they received the least support from the municipal government when they had expected more [74]. This lack of institutional support was misaligned with resident expectations, which led to distrust in the institution because of what residents perceived as a lack of capacity and preparedness.

Two-way relationships occur when there is evidence of two barriers affecting each other. For instance, directional relationships are present between both Institutional Support and Knowledge (see Table 2). Evidence suggests that institutional support directly affected the level of individual and/or organizational knowledge. For example, available government support to residents was frequently not well-publicized, limiting the residents’ knowledge of rebuilding options [11] and leaving them unaware of how to access available resources. The data also suggests a relationship in the other direction, as the degree of knowledge affected the level of institutional support. For example, institutions’ incomplete knowledge of the local needs and context led to inadequate or denied support to residents, often due to issues like Puerto Rico’s complex physical address system [11]. Thus, institutional knowledge gaps in local needs led to insufficient support for residents.

A particularly interesting subset of two-way relationships were mutually reinforcing, as highlighted in Table 2. This type of relationship is seen between barriers Culture and Knowledge. Data suggest there is a prevalent culture of informal self-building where residents rely on personal efforts and assistance from friends and family [43]. This culture of self-help leverages friends/family assistance [105] but limits the acquisition of knowledge related to professional construction techniques. Consequently, a lack of formal construction knowledge perpetuates the cycle of informal housing and potentially unsafe building practices, leaving residents to construct homes based on their limited understanding [44]. These interconnected dynamics reinforce both the informal building culture and the residents’ deficient construction knowledge, creating a self-perpetuating loop.

It is essential to consider these different types of relationships among barriers to fully address the problem. Understanding the directionality of these relationships is crucial for considering how changes to one barrier might affect the others. However, the mutually reinforcing relationships present a particular challenge, as they lack a clear starting point for intervention. This means that overcoming one barrier often requires simultaneously addressing others. Although this research focused on binary relationships between barriers, more complex connections involving more than two barriers are also possible, as not all relationships between barriers have been comprehensively studied. Given the multifaceted nature of informal housing issues, solutions must be developed with an awareness of how barriers interrelate. As the relationships among the barriers become more complex, the solutions must also evolve to ensure they are comprehensive and sustainable.

These findings also align with ongoing recovery policy frameworks, including FEMA’s revised documentation requirements and Puerto Rico’s housing initiatives [50,52]. The barrier framework can serve as an evaluative lens for assessing how these programs address gaps in enforcement, institutional support, and cultural considerations. Integrating such analysis could help ensure that future recovery funding promotes long-term formalization and safer reconstruction practices. Puerto Rico faces significant disaster risks, and it is expected that future losses to housing stocks and infrastructure will occur. As mentioned at the outset, building back better in disaster reconstruction efforts will drive improvement. However, it is equally important to address these barriers and their connections proactively through targeted policies and programs. Relying solely on reactionary reconstruction measures in the wake of disasters is insufficient for assisting residents trapped in the Informal Housing Cycle. A comprehensive approach for disrupting the Informal Housing Cycle must involve concerted efforts in each relevant area to affect meaningful and enduring progress.

6. Conclusions

Informal housing experiences a disproportionate amount of catastrophic damage during natural hazard events due to poor quality construction and lack of resiliency—as demonstrated in Puerto Rico during the 2017 hurricanes and 2020 earthquakes. The issue of informal housing, particularly in disaster-prone regions like Puerto Rico, highlights significant challenges in achieving safe, sustainable, and resilient housing solutions. This research project was motivated by a lack of comprehensive information on understanding the dynamics of informal housing, particularly in disaster-prone regions.

There is an abundance of literature addressing the global challenge of housing in a disaster context. However, these primarily focus on housing types, technical/structural explanations of failures, and recommended remediation techniques. What is surprising is that despite our awareness of natural hazard risks to residential structures—especially informal housing—we continue to see a cycle of damage to inadequately constructed buildings and subsequent reconstruction using the same methods. This is especially troubling because it disproportionately affects poor and vulnerable populations. The interdisciplinarity aspects of this dynamic and cyclical nature of the issue have not been well studied. This led us to pose the motivating questions ‘If we understand technically how to build structures capable of withstanding disaster events, why do natural hazards continue to cause such widespread damage to residential structures?’ and ‘Why are damaged structures often rebuilt using the same methods employed originally?’ Using Puerto Rico as a case study, we sought to derive a more holistic understanding of the factors, their interdisciplinarity, and their connections to natural hazards and informal housing.

This study sought to identify factors contributing to informal housing in Puerto Rico through a coupled systematic literature review and qualitative content analysis approach. We searched academic databases for informal housing related literature and applied defined inclusion and exclusion criteria, resulting in a dataset of 42 documents that included peer-reviewed articles, dissertations, and government reports. The analysis followed a structured coding process in which text segments were systematically labeled and organized into categories. This approach enabled us to integrate evidence from diverse sources, balance technical and nontechnical perspectives, and build a comprehensive multi-disciplinary understanding of informal housing in the context of disaster recovery.

The analysis revealed seven interrelated barriers—Knowledge, Perceptions, Government Dynamics, Institutional Support, Enforcement, Culture, and Resources—that together perpetuate a cycle of informal housing and vulnerability in Puerto Rico. These barriers not only increase the risks faced by disadvantaged populations during disasters but also complicate recovery efforts, as residents often rebuild using the same informal methods. Breaking this cycle requires interventions that extend beyond technical improvements to housing design and construction. Holistic strategies should combine education and training, streamlined policies, stronger institutional support, and culturally sensitive approaches that respect community ties while promoting safer practices. Addressing these barriers in an integrated way can help disrupt the repetition of informal construction and foster more resilient and equitable housing outcomes in Puerto Rico. Although this study centers on Puerto Rico, the seven-barrier framework and Informal Housing Cycle are adaptable to other disaster-prone contexts. Applying this approach to different regions could reveal which drivers of informality are globally recurrent and which are unique to specific governance structures or cultural settings.

6.1. Contributions

6.1.1. Practical Contribution

This research identified seven broad factors connecting informal housing and the effects of natural disasters. These factors are clear barriers to safe and sustainable housing in Puerto Rico. Because these barriers are interdisciplinary, comprehensive approaches are required to minimize the damaging effects of natural hazards to informal housing. In other words, mitigating damage to informal housing stocks cannot be solved with a strictly built environment perspective. Understanding the structural nature of the problem and generating technical solutions to physically strengthen housing is comparatively easy. However, shifting cultural paradigms, appropriating sufficient resources, and overcoming nontechnical barriers is more difficult. The grand challenge in reducing damage to the informal housing sector lies in combining technical knowledge with an understanding of the social context, while engaging all stakeholders to develop enduring and sustainable outcomes.

Improving housing conditions in Puerto Rico is a priority of multiple organizations, including local and federal governments and NGOs. Practitioners in these organizations are more likely to succeed in addressing informal housing by understanding residents’ perceptions, cultural framework, and available resources, while focusing on enforcement, institutional support, and government policies. Integrating solutions that consider how barriers relate is essential when designing programs and policies aimed at improving housing from historically informal practices. Some examples include improving communication to build trust so that residents are more willing to rely on institutional support, and enabling institutions and governments to deepen their understanding of community needs to identify resources for meaningful change—such as educational opportunities and long-term support beyond short-term aid. These changes can be implemented immediately and are likely to significantly improve housing safety and sustainability in Puerto Rico. For example, municipal governments can streamline permitting and expand inspections, NGOs and universities can design training programs in safe self-building and code compliance, and financial institutions and federal agencies can adapt aid and microloan mechanisms to reach households without formal land titles.

The seven-barrier framework offers a practical diagnostic tool for identifying where recovery and housing programs may be failing. Practitioners can use it to prioritize interventions that address multiple barriers simultaneously—for example, pairing construction training (knowledge) with microfinance access (resources). Embedding such combined approaches into municipal recovery plans and NGO initiatives can enhance both efficiency and long-term resilience.

6.1.2. Theoretical Contribution

This research presents a detailed understanding of the links between disasters and informal housing in Puerto Rico. The Informal Housing Cycle demonstrates the circular nature of informal housing damage and reconstruction. It begins with residents building unsafe structures due to cultural practices or financial constraints, compounded by weak code enforcement. After disasters, limited aid to these homes erodes trust in institutions, perpetuating the cycle of informal construction. Breaking this cycle will require innovative, cross-disciplinary social and built environment-based solutions. This necessitates deliberate effort, as many of the barriers, such as the ingrained culture of informal construction in Puerto Rico, are difficult to overcome. This research further demonstrates the complexity of the relationships that exist between barriers. Binary connections between the barriers were explored and several different types of relationships were identified. This research has provided a first look at the interrelated nature of these barriers. However, additional research is necessary to better understand the relationships among barriers and the stakeholders who both influence and are affected by them, as well as to develop and implement effective interventions to disrupt the Informal Housing Cycle.

The Informal Housing Cycle highlights the complex interplay of social, cultural, and institutional factors that perpetuate informal housing practices. This cycle underscores the need for a multifaceted approach to effectively address housing issues. Natural disasters expose the vulnerabilities of informal structures, revealing gaps in support systems that leave residents struggling to rebuild. To break this cycle, it is essential to enhance regulatory frameworks, streamline permitting processes, and build stronger, trust-based relationships between institutions and communities. Only through comprehensive and collaborative efforts can Puerto Rico develop sustainable housing solutions that improve resilience and security for its residents. This research gives practitioners and academics a broader perspective to inform the development of solutions and interventions. The framework also bridges engineering, planning, and social policy perspectives, offering a common structure for interdisciplinary collaboration on housing resilience.

6.2. Limitations of the Study

This study has a few limitations. Although a comprehensive research approach was followed, documents were selected from a vast array of potential literature options and involved making early judgments about their relevance. Consequently, some pertinent literature may have been overlooked in the vetting process. Additionally, this research reflects the literature available at the time of the study and was heavily influenced by literature related to the 2017 hurricanes and 2020 earthquakes. However, literature for studies performed prior to these disaster events might include a different context. Moreover, this research may not capture or reflect all policy and procedural changes resulting from lessons learned from recent events. Consequently, the literature used may not fully reflect the most current developments, particularly as new practices continue to emerge.

Another limitation of this study is the absence of a spatial or territorial dimension. Puerto Rico is a geographically and socially diverse island, and informal housing dynamics may vary significantly across urban and rural contexts as well as between coastal and interior regions. Future work should integrate spatial perspectives—such as mapping informal housing clusters, overlaying hazard zones, and comparing regional enforcement patterns—to clarify how geography shapes vulnerability and recovery.

While this study identified key barriers to informal housing, it did not translate them into measurable indicators. Future research could address this gap by developing qualitative or mixed-method indicators for each barrier, since this step was beyond the scope of our literature-based analysis. For example, survey items or interview guides could be designed to capture perceptions of building safety, experiences with permitting processes, or access to land titles and insurance. Mixed-method approaches could also link qualitative insights with spatial or socioeconomic data to show how barriers vary across contexts. Taking steps toward operationalization would enhance the transferability of the results and support more targeted interventions.

Finally, this research focused on a post-disaster context within Puerto Rico. While we aim to apply these insights globally, the specific government structures and informal housing dynamics vary across different regions. Consequently, not all findings may be directly applicable elsewhere. Variations in government frameworks and local conditions might lead to different barriers and solutions. Nevertheless, this study serves as a starting point for further research and the development of context-specific solutions.

6.3. Future Research

Although this research explored barriers to safe and resilient housing, further efforts are necessary to identify approaches to eliminate informal housing practices in Puerto Rico. Therefore, future research should focus on confirming these results with local stakeholders by conducting interviews with Puerto Rico residents, industry professionals, and government officials. Literature analysis can provide valuable insights into informal housing, but it is limited in its ability to capture lived experiences. Subjective factors such as culture, cognition, and everyday decision-making are best understood through direct engagement with affected communities. Future research should therefore incorporate fieldwork—such as interviews, focus groups, or ethnographic methods—to better capture these dimensions. Such efforts would provide richer understanding of how residents perceive risks, negotiate trade-offs, and make construction choices, ultimately strengthening the applicability of the framework developed here. This approach could potentially identify other barriers to safe and sustainable housing.

Additional efforts are also needed to better understand the complex interconnected relationships that exist between the barriers to safe and sustainable housing. As stated previously, these barriers are not stand-alone issues that can be treated individually. This research only considered binary relationships, but more exploration is needed regarding the interrelated nature of multiple barriers. Finally, we also recommend further research on defining barriers as external or internal issues, thus distinguishing and prioritizing those that should be addressed first. This should include a focus on the sensitivity effects of the various barriers and identification of those which have stronger connections. These efforts should focus on uncovering the nuances of barrier relationships and their interdisciplinary nature by identifying stakeholder needs, policies, and programs that can address the root causes of the Informal Housing Cycle. It is only through thoroughly understanding how these barriers interact and exacerbate the continuation of the Informal Housing Cycle that researchers can begin to find solutions for safe and sustainable housing.

While Puerto Rico serves as a specific case study, the issue of informal housing extends globally, affecting many natural disaster-prone regions. We recommend further research on both territories and independent nations that have high rates of informal housing and high occurrences of natural disasters. This could help distinguish what barriers are specific to Puerto Rico, territories in general, or independent nations. Categorizing these barriers across various locations and natural disaster types would likely reveal patterns and similar barriers that would require similar solutions. These solutions could potentially be applied across different post-disaster informal housing situations in other global areas also seeking safer and more sustainable housing solutions.