Incremental Housing - the Case for Slums and Beyond

Incremental housing in Indian slums (“Image Source”)

Basic brick walls are roofed by a sheet of tarpaulin, vaulted upward for drainage by a singular bamboo pole. Soon tin sheets replace the tarp, which leaks under heavy rains. Walls are expanded as a new addition is formed, and beams are laid under a vaulted roof for attic storage. With reinforced walls, a second story emerges — a shared workspace for family members and immediate neighbors. Adjoining workspaces are combined to maximize utility, and a spiral staircase allows street access to roof storage above.

Such is the de-facto process of incremental housing, a time-lapse visualization of how the urban animal demonstrates organic growth in relatively short periods across the Indian subcontinent. Left to their own means, residents in slums and informal settlements make gradual upgrades to their homes and neighborhoods as land, finance, and materials allow.

However, such ad hoc and unregulated informal settlement upgrading techniques can lead (at worst) to unsafe construction, and at best, vulnerability to disasters or decomposition. Aside from the security of tenure, residents lack the initial investment for decent housing — a structural foundation that is strong enough to support future expansion and adaptable enough to accommodate evolving design needs.

This article summarizes how incremental housing offers governments, community organizers, and NGOs a model for housing the urban poor that optimizes costs alongside community buy-in. While incremental housing has grown and developed from slums and informal settlements, lessons can (and should) be applied beyond the global South as an urban planning framework for large-scale housing programs to support more resilient, accessible, and energy-efficient cities.

Why Incremental Housing

Incremental housing allows for custom configurations (“Image Source”)

Incremental housing is defined as the gradual process by which buildings and community structures are provided in an unfinished form for residents to customize and upgrade as per their needs and access to materials and finance. According to the World Bank, up to 49% of India’s urban population lives in slums — incremental housing allows builders and communities to share equally in the housing process.

In a slum context, incremental housing improves access to basic housing while allowing for gradual improvements over time rather than a large up-front investment. Incremental housing benefits those who:

• Have limited access to finance

• Require multi-use or adaptable spaces

• Aren’t guaranteed land tenure

Rationale and Applications

1) Urban development and management

At the heart of incremental housing is the understanding that households and providers (public, private, and civic sector actors) work in tandem on a solution that benefits both. Writing for the Cities Alliance, Patrick Wakely and Elizabeth Riley hold that with incremental housing, “government does what households cannot effectively do — assemble land and provide trunk infrastructure and services — and households do what governments cannot do efficiently, construct affordable dwellings that meet the priorities and resources of their occupants.”

When the rate of urbanization outpaces the government’s ability to provide equitable services, incremental housing offers operational feasibility with an acceptable degree of quality control.

Pop-Up Housing’s $100 Half-a-House Frame (“Image Source”)

2) Safety and regulation

When governments develop incremental housing strategies, they invest in the future city. By formalizing the provision of land, base infrastructure, and building practices within slum or migrant areas, they pave the way for better land use and greater resilience to disaster as the city develops. When cities implement a standardized incremental strategy for low-income developments as part of the overall urban development approach, they minimize the need for ad hoc interventions over time.

3) Sustainability

In most slums around the world, recycling isn’t simply a source of income, it’s a way of life. As a high degree of recycling and waste treatment happens in and around these areas, they offer an abundance of recycled, repurposed, or upcycled materials which residents can use to upgrade or expand incremental structures. Local materials, labor, and minimal transport requirements make this form of construction competitively sustainable at scale compared to conventional methods.

4) Community involvement

Sustainability also depends on user adoption — ultimately, end-users feeling a sense of ownership over their incremental structure. Scandalous examples of slum dwellers illegally selling government-allotted flats abound. While local authorities paint these slum residents as ungrateful or unscrupulous, the fact remains that the finished structures were not designed alongside, or for, those who would use them.

Slum redevelopment project in Mumbai (“Image Source”)

5) Access to finance

Incremental housing allows individual households to “synchronize investment in buildings and community facilities with the rhythm of social and economic change.” The ability to appropriate and repay smaller loans within a shorter timeframe safeguards vulnerable populations from the risks that might come from taking on larger debts.

Organizations Supporting Incremental Housing

The following organizations offer a model, structural solution, and resources for end-users to be able to complete their structures. This list is not exhaustive, but manages to convey the basic tenets of an incremental housing strategy.

SPARC India (Filipe Balestra and Sara Göransson, architects) — Mumbai, India

Elemental (Alejandro Aravena, architect) — Santiago, Chile

Model

The Society for the Promotion of Area Resource Centers (SPARC) is an NGO that began in 1984 with the mission of serving Mumbai’s urban poor. SPARC partners with designers, architects, and urban planners to provide incremental housing upgrades and financing resources in communities across India.

Structure

An international and interdisciplinary team collaborated to identify a comprehensive strategy for incremental housing in India. After conducting thorough mapping and needs assessment, the team arrived at three housing typologies varying in height and incremental capacity (House B, featured above, includes three storys with an incremental ground floor for parking or commercial use.

Services

SPARC offers access to financing for both incremental or in-situ upgrading. The NGO also works to provide community-level health and sanitation facilities.Write your text here...

‘House B’ typology for Mumbai slum (“Image Source”)

Model

Elemental’s head architect Alejandro Aravena makes open-source plans available for governments to replicate where there is a need for disaster-resistant (specifically earthquake) housing.

Structure

The firm provides a half-filled frame for residents to complete when they are able. Even half-filled, the house provides adequate shelter and protection from Chile’s earthquakes.

Services

Elemental provides expansion plans for residents to choose from. Elemental works closely with local governments to ensure adherence to local building codes and to promote the idea that social housing need not be seen as a formidable investment risk.

Low-income housing development with Elemental half-houses (“Image Source”)

Model

Pop-Up Housing works with private donors, local government, and NGOs to provide incremental housing structures through its $100 Half-a-House program. Pop-Up Housing is a socially focused NGO aiming to make truck infrastructure affordable, adaptable, and replicable in slum areas and migrant settlements across India.

Structure

The structure is made from bolted slotted metal angles. Lightweight yet rigid, metal angles can be assembled into load-bearing frames without special tools or skills. Pop-Up Housing provides these basic frames free of cost to the end user, who is left to finish the house (wall panels, roofing, utility hookups, etc) themselves.

Services

Pop-Up Housing works within a network of NGOs and recyclers to source materials and services to finish the Half-a-House, including recycled plastic composite material, locally-made furnishings, micro-financing, and basic utilities.

Pop-Up Housing (Founder Sampath Althur) — Bangalore, India

Pop-Up Housing uses a network of volunteers to assemble incremental housing frames from slotted metal angles secured with nuts and bolts (“Image Source”)

Applications Beyond Slums

Homelessness

Homelessness is a growing issue in the US, one inextricably linked to deficiencies in the housing market, public health services, and social mobility norms. Over half a million people are homeless in the US, accounting for around 0.17% of the population. Tiny home settlements have emerged as a means to house homeless populations, offered for free or at a subsidized cost contingent upon seeking employment or performing service.

While the model itself is a step in the right direction, the developmental framework behind tiny home settlements is inherently limited. The homes themselves are completed without room to expand; these neighborhoods act as a stopgap between homelessness and permanent accommodation for those climbing the societal ladder.

By introducing incremental housing in place of tiny homes, residents might be able to improve these houses as they are able, building micro-equity through investment in their own housing structures. Referring to the community involvement angle listed above, applying incremental housing incentives within these development programs might do better to produce a more holistic psycho-social effect.

Tiny homes for the homeless in the US (“Image Source”)

Prefabricated and modular buildings

Prefabrication saves time and resources during the construction process, and modular construction allows for dwellings or structures to be expanded in the future. While both terms are in vogue in both industrial and residential applications, neither budgets for a household’s DIY capabilities. These methods require heavy machinery to transport modular elements and position them on site — both for initial construction and for later additions or modifications.

Incremental housing empowers the end user to customize their own structure in ways that don’t require special tools or knowledge. Used in conjunction with a modular approach, incremental housing designs would allow households to more easily customize their living and work spaces themselves. Whether through DIY projects or through contracting semi-skilled labor (pouring concrete, framing, or drywall), households would be able to improve their existing structures without needing to replace or implement more heavy, load-bearing structural elements.

Conventional modular construction using heavy machinery (“Image Source”)

Emergency and disaster structures

When disaster shelters and emergency response infrastructure is deployed, it is often in the form of flat-packed structures or modular arrangements. While financing over time and land tenure are not factors at play, scarcity of resources and space (during transport) remain consistent with those of a slum. Through a combination of modular components and multi-use materials to adjoin trunk infrastructure elements, emergency and disaster structures might benefit from greater adaptability and capacity to accommodate locally available materials.

Some local elements are used, such as old tires to secure the roofs (“Image Source”)

Conclusion

Similar to the Lean Startup methodology in business, incremental housing allows households to iterate deliberately, responding to material availability and spatial demand while maintaining an ability to pivot with relatively little cost. The model benefits both state housing providers and households, leveraging what each side does best to efficiently deliver a workable solution. By incorporating (hyperlocal) sustainable materials and labor, incremental housing as a means of pro-poor housing promises long-term sustainability — and provided that trunk infrastructure is well designed — greater resilience to disaster within vulnerable and marginalized communities.

While incremental housing emerged from the mix of limitations and requirements specific to slums, it nonetheless has applications beyond domestic housing. From potential models to address homelessness in developed nations to offering methodological inputs for emerging housing strategies, incremental housing married modular construction with local resources and materials.

Learn more about how we at Pop-Up Housing are designing bottom-up infrastructure for community wellness, education, and livelihood purposes.