1. CONTEXT
There is an urgency to provide more sustainable and affordable models of private dwellings across many developing and rapidly urbanising regions, not just Nepal. Arguably, the world’s climatic future is inextricably linked to how developing regions urbanise. These areas are the locus of future population increases, with 97% of population growth in the next 30 years projected to occur in the developing world (United Nations Population Division 2022). By 2040, nearly all global energy demand growth is expected to come from developing economies, with emissions increasing by 5 billion tonnes while the rest of the world plateaus or declines (IEA 2024). In such developing economies, building operations and construction account for 39% of carbon emissions and spent energy (WGBC 2019). Each tonne of carbon emissions is directly correlated to increases in global temperature that are causing accelerating rates of extreme weather such as drought, flooding, heat waves and typhoons. Because of the substandard construction of many settlements in developing countries, these communities are especially vulnerable to such events. A key agent of causation within this process is the private dwelling. Despite this, development agencies such as the World Bank have ceased all activities in relation to private housing.1 This is typical (and expected) from most governments that instead focus on public planning programmes. However, this sector is often underfunded and cannot meet demand. Nepal currently has no effective public housing initiative and consequently nearly all housing is built by private individuals.
The lack of capacity to regulate standards of housebuilding in terms of seismic and environmental performance means that this private house construction represents a future public risk. The World Bank mobilised nearly US$700 million for post-earthquake reconstruction in 2015 (World Bank 2015). Haphazard sprawl driven by private house construction using concrete frame is consuming arable land, with 300–450 km2 of agricultural land lost between 1989 and 2016 (Ishtiaque et al. 2017). Unplanned expansion increasingly overlaps with increasing risks in relation to landslides, flooding and the consequential damage to infrastructure (Mesta et al. 2022). Collectively, these dynamics magnify Nepal’s vulnerability to climate disasters, with future events projected to impose US$100–200 million in direct costs annually by mid-century, in addition to wider economic losses of 2–3% of gross domestic product (GDP) per year (World Bank 2022).
The Kathmandu Valley in Nepal is currently urbanising at a rate of 6.5% per year, equivalent to the construction of 50,000 homes annually (National Statistics Office 2023). It consists of the ancient settlements of Kathmandu (population: 1.47 million), Lalitpur (300,000) and Bhaktapur (81,000) as well as numerous satellite towns including Dhulikhel, Kirtipur and Madhyapur Thimi. When travelling along the highway from Kathmandu to these settlements, the view across the valley is almost indistinguishable from that of rural China because it is replete with the same ubiquitous three- to four-storey, concrete-frame dwellings which are the dominant typology fuelling urbanisation across these and many more rapidly developing areas (Figure 1). In these snapshots, the only signifiers of local identity are through hand-painted murals on the sides of buildings or decorative features to some openings and rooftops. In contrast, most of these towns contain a historical central core area comprised of temple structures, courtyards, stepped wells (ghats) and narrow stone-paved streets (Korn 1976).
Figure 1
Construction of concrete-frame houses in the Kathmandu Valley, Nepal.
Source: Authors.
The key research objective is to explore the potential of a new typology that offers an alternative to the ubiquity of the concrete-frame house. The aims are: to ascertain the housing needs of owners of vacant sites and to understand the factors related to why they have not yet rebuilt their home; to provide an alternative model of house reconstruction and building assembly that addresses these needs and complies with cultural heritage values; and to provide a framework for future policy change to adopt the new typology.
The research focuses on Lalitpur, Nepal’s fourth most populous city and one of the key cities comprising the Kathmandu Valley’s metropolitan area. Located centrally within its historic core is Patan Durbar Square, a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site. The scope of the study focuses on a 500-m radius from this origin point that encompasses over 1500 potential infill sites identified by the authors. The focus is to consider how these plots will be rebuilt, in what form, construction logic and material system? Currently, owners of damaged or destroyed old family houses often cannot resolve land tenure issues, choosing to subdivide their plots and build independently. Due to pressures on land availability and high costs, new construction on these small plots typically takes the form of concrete-frame, mini-pencil tower buildings of six to seven stories. These buildings represent future seismic risk due to soft storey failure (Build Change 2015); have a detrimental environmental impact (Bajracharya 2014); and have a negative effect on the traditional urban fabric of the settlement (Ishtiaque et al. 2017). They are reliant on imported concrete and steel and have to comply with building codes which stipulate 14 × 14-inch (35.6 × 35.6 cm) reinforced concrete columns of all structures regardless of plot dimensions (Figure 2).
Figure 2
Examples of the narrow, concrete-frame, pencil houses built on subdivided plots in Lalitpur, Nepal.
Source: Authors.
1.1 TRADITIONAL HOUSE CONSTRUCTION
The predominant typology in the historical core of Lalitpur is the Newari house (Figure 3), the name given to the traditional housing structure of the Newar people, the traditional settlers of the Kathmandu Valley. These buildings have a unique construction system comprised of a timber structure embedded within four layers of brick that can be 12–18 inches (30.5–45.7 cm) thick. The timber contains horizontal ring beams carefully tied to vertical columns and horizontal floor joists. This stiffens the entire structure enabling it to withstand many of the complex forces associated with a seismic event. The brick is loadbearing and remains in compression, becoming thinner on each floor as it extends upwards. These buildings are generally 6 m in depth, and each house is divided by a structural spine wall that divides each floor into two rooms. Floors are made with timber joists and floorboards and finished with red clay. The roof is a timber structure clad in terracotta tiles, with a strut-propped overhang that protects the street from monsoon downpours. Windows and doors are often intricately carved from locally supplied ‘Sal’ wood (Shorea robusta) known for its hardness and durability. The oldest homes, around two centuries old, feature square, latticed and ornately carved windows (San Jhya), and some have the San Jhya in the family’s main living room with a bench and latticed openings intended for discrete viewing of the street (Korn 1976). The Newari house, like many vernacular structures, has evolved according to the specific constraints of its locale, including climate and available resources. The house is typically shared between multi-generational families, with the first and second floors used as living and sleeping areas and the upper floor as a collective kitchen. The attic is reserved as the family shrine and not accessible to guests.
Figure 3
The predominant typology in historical core areas is the Newari house.
Source: Authors.
In the aftermath of the Ghorka earthquake in 2015, around 474,025 of these traditionally constructed houses were destroyed, representing 95% of all buildings lost. A further 173,867 were condemned as unsafe, contributing to 67% of the total number of damaged buildings. Some districts, such as Sankhu, lost as many as 70% of their total Newari building stock (National Planning Commission 2015). Despite these data, local practitioners, such as Rohit Ranjitkar of the Kathmandu Valley Preservation Trust (KVPT),2 claim that a well-constructed Newari home will remain unharmed by seismic activity due to the intelligence of its structure. However, reporting international authorities, such as the Earthquake Engineering Field Investigation Team (EFFIT), have not been able to verify these claims because there is such significant variance in building details of these structures. For instance, variations in mortar type, thicknesses of the walls and types of bricks or stones all contribute to discrepancies when measuring the seismic resilience of these buildings (Adhikari & D’Ayala 2020).
1.2 OBSOLESCENCE OF THE VERNACULAR
Despite mounting efforts from conservationists, building in the traditional manner is also no longer popular amongst residents. Traditionally built buildings with the necessary timber detailing can be as much as 74% more expensive than concrete-frame brick-infill construction.3 Despite Sal timber being priced at approximately NPR300/ft3 at source (the forest front), in urban retail markets the same timber was sold for NPR4000–5000/ft3—a mark-up of over 13 times—primarily driven by corruption and informal trade dynamics (Banjade et al. 2011). These costs are compounded by the rising costs of skilled carpenters, mainly due to the increasing scarcity of local artisans. In 2013–14 alone, nearly 0.5 million Nepali youth—many with construction and carpentry skills—obtained labour permits to work abroad, draining the domestic workforce needed for seismically resilient traditional housing (ILO Nepal & GIZ Nepal 2014).
However, the shift away from traditional construction and the introduction of reinforced concrete began in the 1950s, following Nepal’s political opening after the fall after over a century of the Rana regime. Foreign aid and international development agencies together with the 1969 Physical Development Plan promoted ‘modern’ building practices that set the stage for a new type of residential architecture for the Kathmandu Valley. By the 1970s, increasing exposure to global media and foreign influence helped reframe housing ideals around detached, suburban-style bungalows, which gradually replaced the clustered Newar settlements. These concrete-frame and brick-infill houses allowed for incremental vertical and horizontal expansion while promising modern amenities and privacy. This shift also marked the beginning of urban sprawl in the Kathmandu Valley: between 1971 and 1981 the residential land area doubled, and by the year 2000 peripheral agricultural land had fallen from 62% to 42% (Sengupta & Bhattarai Upadhyaya 2016).
A series of planning studies and policies were tested over the following decades, but were unable to control the settlement’s growth and transformation. Kathmandu’s urbanisation rate accelerated from 3.6% in 1991 to 6.5% in 2001 due to several factors, including: rural–urban migration during the 1996–2006 civil war; the shift towards rental tenancy that grew from 23% in 1991 to 59% in 2010; and the demand from an increasing middle class requiring ‘modern’ amenities, such as private parking, air-conditioning and contemporary construction materials. A study using remote-sensing and modelling predicts that the growth of built-up areas in the Kathmandu Valley that grew from 41 km2 in 1975 to 177 km2 in 2018 will double again by 2050 (to 352 km2) (Mesta et al. 2022).
Additionally, the number of financial institutions doubled in Kathmandu between 2000 and 2010, reflecting the emergence of a financialised real estate market. The consequential urbanisation led to escalating land prices, which increased by 300% between 2003 and 2017, and propelled concrete-frame buildings as the most affordable and rapid form of construction (Ishtiaque et al. 2017).
The 2015 Ghorka earthquake further exacerbated these issues. The clearing of damaged buildings, as well as the demolition of intact traditional buildings in fear of their future failure, or as an excuse for subdivision, has resulted in the creation of many empty vacant sites. This has led to problems related to the lack of clear records of landownership, and emerging disputes between generational families. For example, land is inherited and passed down from father to son. When there is more than one son, land is subdivided equally. The escalating costs of land in Kathmandu has furthered the demand for owning individual land title rather than maintaining shared ownership with one’s siblings. This has had a two-fold impact. First, it has furthered the demolition of traditional houses as they are not easily subdivided into individual homes, and so the easiest way to resolve disputes is by clearing the land. Second, on vacant sites, land is subdivided into small plots, resulting in very narrow houses, each of which contains its own vertical circulation. This reduces the area for living space, resulting in rooms that are often as small as 15% of municipal recommendations (UN-Habitat 2010). In some cases, existing houses are physically split and redeveloped while the original half is still occupied.
In resistance to the replication of concrete-frame homes, active practitioners in Nepal are promoting traditional building techniques and keen to preserve the cultural heritage aesthetic of central core areas. These include Rapindra Puri, a director of a vocational school in Bhaktapur, and Dr Rohit Ranjitkar, a conservation architect and Director of the KVPT.
Ranjitkar’s KVPT offers training programmes primarily focused on the rehabilitation of historic monuments; however, the trust has supported a community of homeowners in the historic centre of Patan to rehabilitate their homes using materials salvaged from the earthquake. Puri established vocational academies in 2015 in Panauti and in 2020 in Bhaktapur to create a supply of capable craftsmen to restore traditional houses. These practices demonstrate models of restoration practices in Kathmandu’s post-earthquake condition. However, these methods tend to favour heritage monuments or an emergent tourist economy based on traditional homestays, hotels or restaurants. In the context of Kathmandu’s contemporary pressures of urbanisation, the vernacular typology is not scalable to address the demand for speed of construction, material costs, skilled labour and more flexible spatial organisations demanded by residents.
However, Puri has also been involved in effecting policy in building regulations in historic centres to promote a public subsidy in support of residents rebuilding their traditional homes. The subsidy works as a scaled ‘A, B, C, D’ model as follows (where A has the largest subsidy and D the lowest): preserving or retrofitting an existing historical house (A); building new houses with traditional materials according to vernacular typologies when the original homes are lost (B); updating the facades of existing concrete houses with heritage elements (C); and building new concrete-framed houses using traditional facades (D).4
Although the ‘A, B, C, D’ heritage subsidy model is successful in promoting a vernacular aesthetic within historic urban centres, this has resulted in the aestheticisation of an idealised Newari architecture that does not account for issues regarding structural or environmental performance or acknowledges specific contextual differences in building type or facade treatment. For example, the practice of building brick facades on concrete-frame structures (C, D) may be prone to earthquake failure if brick facades are not horizontally tied back and stiffened, and if ground floors are left open for commercial activities and therefore are subject to soft-storey failure.
1.3 EMBODIED CARBON AND CONSTRUCTION EMISSIONS
Beyond the effects of this transformation on the traditional urban fabric, these processes have significant climatic implications which are representative of broader patterns occurring in rapidly urbanising regions similar to the Kathmandu Valley. The erasure and replacement of traditional structures with concrete frames, combined with the haphazard sprawl of new concrete-frame construction into areas of arable land within the valley, has created environmental pressures with both local and global ramifications (Muzzini & Aparicio 2012; Sengupta & Bhattarai Upadhyaya 2016).
The material transition from traditional to concrete construction carries substantial carbon implications at both building and settlement scales (Crawford et al. 2010). The baseline assessment of 15 representative buildings in Lalitpur’s core revealed that concrete-frame construction generates 0.40 t CO2e/m2 in cradle-to-gate emissions, compared with 0.28 t CO2e/m2 for traditional Newari construction—a 30% difference attributable to the embodied carbon intensity of cement, steel reinforcement and industrial brick production versus locally sourced timber and clay-based materials.5 When extrapolated across the 1540 identified infill sites within the study’s 500-m radius—each averaging 484 ft2 (45 m2) over four stories—continuing current concrete-frame practices would generate approximately 11,088 t CO2e, compared with 7761 t CO2e if traditional construction methods were used. This 3327 tonne difference within a single ward represents the annual carbon sequestration capacity of approximately 38,000 trees.
At the scale of the entire Kathmandu Valley, these figures become more consequential. With an annual urbanisation rate of 6.5% producing 50,000 homes per year (National Statistics Office 2023), the cumulative embodied carbon impact of concrete-frame construction amounts to approximately 360,000 t CO2e annually in construction-phase emissions alone (Mesta et al. 2022). Over a decade, this totals 3.6 million tonnes—equivalent to the annual emissions of 780,000 passenger vehicles (EPA 2024). This construction pattern mirrors broader Global South trends where 80% of future building construction is projected to occur, yet where capacity for low-carbon alternatives remains underdeveloped (GlobalABC 2025). Unlike regions implementing embodied carbon regulations and material efficiency standards, rapidly urbanising contexts prioritise speed and cost, perpetuating the reliance on carbon-intensive materials, despite their climatic consequences (Crawford et al. 2010; Scalisi & Sposito 2019).
The material supply chain further compounds the environmental impact. Nepal’s construction sector depends on cement and steel that require energy-intensive manufacturing processes—with fired brick production alone accounting for 37% of Nepal’s CO2 emissions from combustion (UNDP 2025). Steel reinforcement requirements in concrete construction (1.5–2.0% steel by volume in concrete members) multiplied by steel production emissions create an additional embodied carbon burden estimated at 110–180 kg CO2e/m3 of concrete (Hammond & Jones 2019). The 498,852 homes reconstructed using concrete following the 2015 earthquake represent a substantial increase in Nepal’s carbon footprint (National Reconstruction Authority 2021), establishing a precedent that continues to shape reconstruction and new development across the valley. This reliance on imported cement and steel offers limited economic benefit to local communities compared with traditional construction’s use of locally sourced materials and craft labour (Adhikari & D’Ayala 2020), while locking the valley into carbon-intensive building practices for decades given typical building lifespans of 50–100 years (Scalisi & Sposito 2019).
2. METHODS
This study employed a mixed-methods approach that integrates spatial analysis, environmental monitoring, embodied carbon assessment, household surveys and participatory stakeholder consultation. The methodology was structured as an iterative process where each phase informed the specification and evaluation criteria for subsequent phases, culminating in prototype designs that respond to measured baseline conditions. These prototypes and their construction and material systems offer an alternative model for house construction, paving the way for policy amendments to incentivise seismically resilient house construction with improved environmental performance. The method consists of the following components.
2.1 SPATIAL ANALYSIS AND BASELINE SCOPING
A comprehensive geographical information system (GIS) survey conducted between January and March 2024 in a 500-m radius from Patan Durbar Square mapped and categorised 1540 infill sites according to their current state and plot dimensions.6 This spatial analysis established the scope of intervention—determining the range of plot dimensions and site constraints that would define the design parameters for prototype development. From this survey, 15 representative building types across three construction categories (traditional Newari, concrete frame and hybrid) were selected for detailed measured surveys. The resulting architectural drawings established the dimensional and material data necessary for subsequent embodied carbon assessments, baseline environmental performance monitoring and comparison with prototype designs.
2.2 EMBODIED CARBON ASSESSMENT FRAMEWORK
To establish baseline carbon performance across existing construction systems, material volumes extracted from measured building surveys were assessed using a standardised methodology. The assessment focused on product stages (A1–A3) of the building life-cycle—raw material extraction, transport and manufacturing—collectively termed ‘cradle-to-gate’ emissions. This scope captures the phase where material selection decisions have greatest impact.
For each material (reinforced concrete, steel reinforcement, fired clay bricks and timber), material volumes were quantified from architectural drawings and multiplied by global warming potential values (kg CO2e). Steel reinforcement quantities in concrete elements were estimated using typical assumptions for reinforced concrete construction in Nepal. Emission factors were sourced from Environmental Product Declarations via the OneClickLCA database,7 selecting materials representative of Nepali construction contexts. Results were normalised per m2 of gross floor area to enable comparison across buildings of different sizes.
This methodology was applied consistently to both baseline buildings and prototype designs, enabling direct comparative assessment and identification of embodied carbon reduction opportunities.
2.3 ENVIRONMENTAL PERFORMANCE MONITORING
Four houses representative of different construction assemblies (one traditional, one concrete frame, two hybrid) located along the same street within 100 m of each other were instrumented with Hobo MX1104 temperature/relative humidity/light data loggers.8 Data collected at 2-h intervals from January to December 2024 established the baseline thermal and daylighting performance. These data informed design criteria for prototype specifications, including natural ventilation strategies and window sizing requirements.
2.4 HOUSEHOLD SURVEYS
Semi-structured interviews with 25 households in Chyasal (Ward 9) conducted between January and March 2024 documented household structure, living environment preferences, financial capacity, reconstruction timelines, land tenure issues and construction preferences.9 This survey determined the scope of user requirements—household sizes, affordability constraints and spatial needs—that would define the design brief for prototype development.
2.5 PROTOTYPE DEVELOPMENT AND STAKEHOLDER CONSULTATION
Two prototype systems were developed in collaboration with structural engineers (Prime Consulting Engineers, Hong Kong, China; Earthquake Safety Solutions, Nepal) based on findings from spatial analysis, household surveys, environmental monitoring and baseline carbon assessment. The prototypes were iteratively refined through feedback from multiple stakeholder groups.
Feedback was gathered through the following:
focus group workshops with six selected households
consultations with Lalitpur Municipality officials, including technical and architectural assessment teams
structured questionnaire surveys with 20 engineers from the National Society for Earthquake Technology (NSET)
workshops with members of The Society of Nepalese Architects (SONA)
meetings with officials from the National Department for Urban Development and Building Construction (DUDBC).
Throughout this consultation process, the embodied carbon methodology was consistently applied to evaluate design iterations, enabling quantification of how different material and structural decisions affected overall carbon performance. Stakeholder feedback—particularly regarding seismic resilience, cultural heritage compatibility, spatial efficiency and affordability—was incorporated into subsequent design revisions. This back and forth between residents, engineers, heritage experts and municipal officials ensured that prototype designs balanced multiple performance criteria while remaining achievable within existing construction practices and economic constraints.
Parallel to design development, discussions with municipal and national policy officials identified the barriers to adoption and opportunities for supporting policy change.
3. EVIDENCE AND RESULTS
3.1 SPATIAL ANALYSIS
Working with a local community non-governmental organisation (NGO), Lumanti, a GIS map was created covering a 500-m radius of Patan Durbar Square in the Lalitpur core area (Figure 4). Each street was surveyed, categorising the current state of the 1540 infill sites. Of these sites, 411 were vacant but used as public green space (Figure 5a); 383 were occupied with temporary single-storey structures (Figure 5b); 150 houses were fully standing, but too damaged to occupy (Figure 5c); 196 houses were completely vacant (Figure 5d); 26 houses had a several stories torn down; and 374 houses were occupied, despite being damaged (Figure 5f). The dimensions of the plot follow the traditional proportions of the Newar settlement, which is based on the typology of the traditional Newari house, maintaining depths of 6 m and widths between 3 and 20 m according to the original household structure. However, due to historical land subdivision, there are currently 447 sites that are < 4 m wide, 507 that are between 4 and 6 m, and 159 sites that are between 6 and 7 m.
Figure 4
Spatial mapping of infill sites in Patan, Lalitpur, 2025.
Source: Base GIS urban data was provided by Lalitpur Municipal City, infill data; mapping by authors.
Figure 5
Different categories of infill site conditions surveyed in Patan, Lalitpur, 2025.
Source: Authors.
All the houses fall under three categories of construction: traditional building techniques using bricks, timber and clay mortar; concrete-frame structures with brick infill; or hybrid systems of the above, typically resulting from additions or extensions to existing buildings. A total of 15 of these types were drawn (Figure 6); it was calculated that the average plan efficiency was approximately 58%, with each member of the household having 11 m2 (compared with 16 m2 in Hong Kong and 25–30 m2 in London).
Figure 6
Hybrid construction showing incremental additions to traditional houses.
Source: Buddha Shrestha and students from Kathmandu University.
From these 15 buildings, four houses representative of different building assemblies (one traditional, one concrete frame and two hybrid) were selected for detailed environmental monitoring. Each house was fitted with a Hobo MX1104 temp/RH/light data logger in the main living space, and three external loggers installed to measure and compare the environmental performance of each building type. The houses were located along the same street with the same north-east orientation, within 100 m of each other. Data collected every 2 h between 10 January and 17 December 2024 revealed very little variation between the different building assemblies.
All four buildings maintained relatively stable temperatures through the year. Despite an external annual temperature between the highest and lowest of 45 K, the internal temperature difference stayed within a range of 17.1 K (concrete frame) and a range of 22.1 K (hybrid). Even when exterior summer temperatures reached to 38.63°C, the interior temperatures of the houses were all at least 10 K lower (the traditional house at 27.4°C, the hybrid houses at 27.1–28.4°C and the concrete frame was the lowest at 25.9°C) demonstrating their ability to regulate temperature. Similarly, the daylight levels did not demonstrate significant differences. All houses received insufficient lighting, with the highest levels of each house ranging between 82 lux (a traditional house) and 143 lux (a hybrid house).
Perhaps the most compelling finding from this fieldwork is that the traditional vernacular construction did not perform significantly better than the concrete frame, which contradicts the dominant understanding of the Newari house as the epitome of a vernacular construction in tune with the logics of available materials and its climatic context.
However, when it comes to embodied carbon, the assessment reveals a markedly different picture. The embodied carbon analysis compared cradle-to-gate emissions (product stages A1–A3: extraction, transport, manufacturing) of the four instrumented buildings. Material volumes were extracted from measured architectural drawings, quantifying primary structural elements: reinforced concrete, steel reinforcement, fired clay bricks and timber.
For each material, volume was multiplied by global warming potentials from Environmental Product Declarations (OneClickLCA database), selected for materials typical of Nepali construction contexts. The traditional Newari house (230 m2 gross floor area) required 20 m3 of Sal timber for the joists and roof, 100 m3 of fired clay brick walls (50 t CO2e), and 3 m3 of brick foundation (6.6 t CO2e), totalling 56.6 t CO2e embodied carbon, or 0.25 t CO2e/m2. Additionally, the 20 m3 of Sal timber stores 17.6 tonnes of biogenic carbon, representing atmospheric carbon sequestered during tree growth and stored in the building’s structure.
The concrete-frame house (190 m2 gross floor area) contained no timber structural elements, 100 m3 of fired clay brick walls (50 t CO2e), 53m3 of concrete structure (20 t CO2e) and 10 m3 of concrete foundation (3.6 t CO2e), totalling 73.6 t CO2e embodied carbon, or 0.4 t CO2e/m2. This building provides no biogenic carbon storage.
Despite the use of fired clay bricks in both construction types, the traditional house construction outperforms the concrete frame by 30% less embodied carbon (0.25 versus 0.40 t CO2e/m2). This difference reflects three factors. First, a reduced reliance on Portland cement (manufacturing accounts for 5–8% of global CO2 emissions), which is replaced by timber structural elements and clay brick walls with lower per unit emissions. Second, the elimination of steel reinforcement in the roof and floor structures through the use of timber joists. Third, the additional biogenic carbon storage benefit of 17.6 tonnes provided by Sal timber, which remains sequestered for the building’s lifetime.
This methodology was applied consistently to all 15 surveyed buildings, establishing baseline embodied carbon performance. The findings reveal that traditional construction achieves superior embodied carbon performance despite using fired clay bricks, a finding that carries significance for reconstruction strategy because it indicates that prioritising low-carbon material selection offers substantial climate benefits.
Based on this comprehensive analysis of existing construction systems, combining empirical environmental monitoring and embodied carbon quantification, the design criteria for the proposed prototypes were established: improve upon the current 58% spatial efficiency; improve thermal performance and reduce embodied carbon compared with current construction methods; maintain affordability comparable with concrete-frame construction; ensure seismic resilience appropriate for Nepal’s Seismic Zone V; and accommodate flexible spatial organisation to address household land disputes and multi-generational living arrangements.
3.2 HOUSEHOLD SURVEYS
From the initial spatial analysis, 25 households and owners of vacant sites were selected from Chyasal (Ward 9), and household interviews were conducted to ascertain their household structure, household needs, financial capacities and status of when they are planning to build. Chyasal was selected as the inhabitants are mainly from the marginalised Shahi caste (Timsina 2022), which has limited their financial capacity, and so many have not been able to reconstruct their homes. The ward also has an active cooperative (Nava Astha Women Cooperative) that functions to provide collective micro-loans to members. This cooperative provided a vital link to enable the research team to mediate relations with the community, but it also represents a future asset to assist residents in obtaining household finance.
The survey revealed that the majority (23 of 25) of homes were damaged during the earthquake in 2015; that only nine families are still living in these homes, with the other 16 living in alternative accommodation; and that all 25 families want to rebuild, with 60% preferring a concrete frame with a traditional brick facade. Ten the families anticipate that they will have to further subdivide their plots based on landownership titles between family members, with 40% responding that lack of available funds was the main reason behind not rebuilding.
The cost of construction for a concrete-frame house is approximately NPR3500–4500/ft2 (US$33.18/ft2) compared with NPR7050/ft2 (US$50.3/ft2) for a traditional house using bricks and timber. The additional expense is due to the high cost of timber used in the floor joists and roof structure, and in terms of material and labour. This means that for a house of four stories with the average plot size in the survey (484 ft2/45 m2), it would cost NPR8,712,000 (US$61,676) for a concrete house compared with NPR13,648,800 (US$97,186) for a traditional house.
Commercial banks offer mortgage products currently at around 8% interest, with a maximum 80% loan-to-value for a first home. However, there are strict eligibility criteria and the need for collateral (Nepal Rastra Bank 2025). Alternatively, member funds (Employees Provident Fund, Citizen Investment Fund, Social Security Fund) offer rates for contributing members employed within a formal sector workforce at around 7.25%, which can be paid off directly through salary deductions. Other options for housing finance include through cooperatives, but usually these are focused more on home improvements than to finance the construction of a new house (Employees Provident Fund 2025). For example, Nava Astha Women Cooperative in Chyasal offers NPR500,000 at a 10% interest rate with no collateral required.10 However, given that in the Kathmandu Valley average household annual income is NPR345,337 (National Statistics Office 2024) and that loans typically amount to NPR350,000 (Nepal Rastra Bank 2024), it means housing finance is a barrier to reconstruction.
The research team comprised two structural consultants: one based in Hong Kong (Prime Consulting Engineers—PCE) and the other in Nepal (Earthquake Safety Solutions—ESS). Working collaboratively, they established principles for reconstruction on these sites to avoid seismic damage. These included avoiding structural pounding from neighbouring buildings by limiting structural connections between buildings; shifting the vertical load path away from the plot boundary; maintaining continuous symmetrical vertical load paths; and maintaining horizontal structural symmetry in plan.
Based on this research of spatial analysis of the current logics of construction for housebuilding, the existing performance of current building types and the needs of residents including their financial capacity, the scope and specification for the proposed prototype were determined: a four-storey house with an accessible roof; to be a similar cost/ft2 as the concrete frame; to improve upon 58% floor plan efficiency;11 to improve upon 0.4 t CO2e/m2 in building embodied energy efficiency; to improve seismic resilience based on key principles; and to improve environmental performance with respect to daylighting and ventilation.
4. ALTERNATIVE MODEL
Two prototypes were developed to test with residents. The first titled ‘Core House’ is designed for plots that are at least 6 × 6 m in extent, approximately numbering 571 within the survey site. The structure is comprised of a central reinforced concrete core containing the stairs with bolted-on steel cantilevered beams to support the floors. This removes the need for any columns or foundations on the site boundary, limiting the impact of potential damage from neighbouring buildings, which was a significant cause of structural failure in 2015. Although timber for the structure was initially examined, it was deemed unfeasible as it would not pass Nepal’s building regulations for a four-storey structure. A full steel structure was also tested; however, the hybrid structure of the reinforced concrete core provided increased seismic performance due to its shear strength.
The core acts as a hall and circulation space for the stairs. This enables the house to be lived in as a single collective house, or split in half vertically, or further separated floor by floor into apartment units. Internal partitions can be freely determined by residents to suit their needs. The provision of this flexibility aims to address the land disputes that have been withholding reconstruction in many infill sites across the valley when inherited land is divided into separate ownership (Figure 7).
Figure 7
Core House prototype.
Source: Authors.
The prototype adheres to the spatial qualities of the traditional settlement by allowing for a flexible ground floor, enabling certain traditional urban features such as an open shop-front, courtyard-to-street passages, and ground floor public spaces for gathering (chayli). While concrete-frame buildings may accommodate these features, this often results in unbraced ground floors that make the structures seismically vulnerable to soft-storey failure. Shifting the load from the external walls to the core frees the facade to allow for more sustainable alternative cladding options than conventional fired bricks. These options include the use of salvaged traditional building components, such as windows and facade elements, which also contributes to the criteria of the heritage settlements. In terms of the prototype’s sustainability, in comparison with the conventional concrete frame, the design reduces the use of concrete by 58%.
However, as previously discussed, many sites have plot widths of less than 6 m and are bounded by adjacent properties on either site, so the Core House would not be a suitable solution. Based on this the ‘Wall House’ was developed which could be applicable to 954 sites within the study. The Wall House utilises a system of brick construction known as the ‘Quetta bond’, which was developed after the 1935 Quetta earthquake in what now has become Pakistan. Effectively, the system uses the cavity between bricks to introduce steel reinforcement and concrete. This means that the masonry wall is reinforced both vertically and horizontally. Similarly to the traditional Newari house, the main structural walls are at the front and back of the plot, which are stitched together with a horizontal ring beam at each floor. This avoids the ‘hammer effect’ from adjacent buildings. Four additional masonry buttresses, two on each side, are added to provide bracing against failure from neighbouring structures which also flank the stairs. This stairwell creates a vertical void through the building, culminating in a skylight. This provides light into the mid-section of the building and enables stack ventilation, drawing air up through the building during hot weather. Floors are made using timber joists, and the roof is constructed of timber trusses following the same logic as the traditional house. Depending on particular by-laws, additional balconies could be added, and the decision on the specific window type, in terms of its level of ornamentation and therefore cost, was left open to residents. The advantage of this system is that it can reuse any existing bricks or reclaimed timbers from the existing property and uses methods of construction familiar to local workers (Figure 8).
Figure 8
Wall House prototype.
Source: Authors.
Based on a needs assessment conducted by Lumanti, six resident households were selected to apply the models, and subsequently based on plot dimensions, the Core House was developed for two households and the Wall House for four families. The intention was to provide each household with a set of drawings and a structural report for submission to the Lalitpur Metropolitan City to gain approval for construction. In a focus group workshop, each household approved the proposed prototypes and wanted to move forward with the building submission process.
To demonstrate that the prototype designs improved upon the baseline assumption of a concrete-frame assembly, three design options for the same plot were generated using three systems of construction: concrete frame, traditional or the Wall House Quetta system. From these digital models, the volumes of material used were calculated in order to estimate the embodied carbon and verified costs using municipality approved standards for material and labour costs. The comparison revealed that the concrete frame was the most affordable (NPR3500–4500/ft2), but with 14.5 t CO2e embodied carbon and none sequestered. For the traditional house, if the bricks were newly fired, cradle-to-gate emissions would reach 30 t CO2e, but with 8 t CO2e stored due to the use of timber, however, it is the most expensive at NPR7050/ft2.12 The Wall House prototype, due to the reuse of bricks and use of timber, represents the most sustainable in terms of embodied carbon, reducing the amount of embodied carbon to 5 t CO2e and sequestering 11.5 t CO2e. In terms of spatial efficiency, the concrete-frame house, due to the 14-inch regulation for column size, is 58%, and the prototype is 70%. Although not necessarily as economical as the concrete frame at approximately NPR4100–5100/ft2, for an additional 10% cost, the benefits of the prototype include embodied carbon, structural resilience, ventilation and spatial efficiency. Based on these findings, the prototypes were presented to stakeholders, including the Lalitpur Municipality, NSET, SONA, heritage professors from Kathmandu University, and the National DUDBC.
5. DISCUSSION
The discussion with the Lalitpur Municipality emphasised that any proposed building type must comply fully with existing by-laws in order to receive municipal support. Their concerns focus primarily on architectural features, including roof slope angles, the presence of cornice details at floor levels, window proportions, and the building’s height and proportion in relationship to its neighbours. Another consideration is that the by-laws are specific to different zones within the city relating to proximity to the historical heritage sites. This would allow variation to take place within the prototype to adjust to these specific criteria. In conversation with Shree Kumar Maharjan (the Urban Project Directorate Divisional Engineer of Lalitpur Metropolitan City), he supported the creation of a building manual alongside potential municipal subsidies for the new type.13
In feedback from 20 engineers from the National Society for Earthquake Technology (NSET), including Dr Amod Mani Dixit, NSET Director, and Dev Maharjan, chief executive officer of NSET affiliate Earthquake Safety Solutions, all supported the value of applying the Wall House prototype and its reinforced masonry system as a viable, affordable and seismically resilient alternative to the concrete frame.14 The survey with engineers had many positive comments regarding the use of locally available materials while adapting traditional modes of construction, the improved plan efficiency, its improved carbon emissions performance and the improved seismic resilience of a wall system relative to the concrete frame. For instance, some remarks from the survey included: ‘the [Wall House] helps to evolve the existing design of traditional houses in the community’; the Wall House ‘is affordable yet structural convincing’; and the Wall House could change the approach to affordable housing due to ‘the inclusion of the wall system in seismic resilience’.15 Dr Amod Mani Dixit, Director of NSET, said that the fundamental advantage of this system of construction was to update the existing techniques of traditional masonry construction while limiting the use of expensive timber in the walls, making it more affordable and easier to maintain. Some engineers recommended using steel to replace the timber floor and roof to improve its affordability.
However, in the consultation with SONA there were many objections to the design.16 Some comments from the survey with SONA suggested the design was ‘diluting the value of Newari architecture’ or that the prototype ‘lacked traditional heritage value’.17 These were focused on the model not adhering to the traditional methods of construction and heritage detailing. The facade design was a critical factor with many raising concerns regarding brickwork and carpentry ornamentation. To some experts in the fields of traditional buildings, the prototype was seen as a threat to their cultural architectural heritage. The counterargument was put that to build in the traditional manner was not a pragmatic solution given its expense, lack of skilled labour, and the contemporary reality of land prices and subdivision; and that the greatest threat to the cultural identity of the core city was the prevailing use of concrete-frame construction. Although some argued that the concrete frame with an infill heritage facade answered issues of cultural identity, given the propensity to build higher on small plots, this way of building still represented an increased seismic risk and perpetuated the use of carbon-intensive materials. At the end of the impassioned discussion, it was agreed that SONA would help contribute to the facade design and acknowledged that the Wall House prototype could be a suitable alternative for core areas. However, they insisted that the Core House type would only be viable outside of inner historic areas on the periphery of the city.
One key objective is to influence the policy direction at a municipal level, but also to test its viability at a national level. To this effect, a meeting was conducted with Prakirna Tuladhar, Deputy Director General, and Machakaji Maharjan, Director General, Building Division, of the National DUDBC.18 The department expressed an interest in formally integrating the proposed building system into Nepal’s National Building Code. However, in order to proceed, the DUDBC requested that memorandums of understanding (MOUs) be set up between the University of Hong Kong and the DUDBC. Although possible, this additional layer of bureaucratic administration will take time (6–12 months) and has no effect on the actual content being generated. This also highlights a discrepancy between national policy, municipal policy and the reality on the ground. In terms of National Policy, the DUDBC made it clear that the current prototype would not comply with the National Building Code and so could not be built; however, from a municipal level, if the building passed the architectural assessment and the structural assessment, permission for construction would be granted.
Following these surveys and workshops, the policy recommendations and next steps were two-fold: the integration of the proposed building system into the National Building Code to make it accessible and readily accessible to residents; and to integrate into the existing heritage subsidy model an additional tier for the use of this proposed seismically resilient building system so that those residents who are either struggling to afford reconstruction or who will build informally to reduce cost may be able to access this form of resilient housing.
6. CONCLUSIONS
Current policies in Nepal (and in many developing regions globally) are not sufficient to regulate the construction of these houses to standards required to address the ensuing climate crisis. The critical point is that the private house sector must not remain overlooked, that new typologies of housing that are affordable and sustainable need to be introduced at scale, and to stem the unabated construction of concrete-frame structures paying little regard to environmental performance and building resilience. The example of Lalitpur in Nepal is a case in point.
The intent of the project is to initiate typological change; arguing that without a change in type, the reversion to universal and generic modes of house construction will continue unabated. Such typological transformation needs to be paralleled with policy change and a recognition that private house construction, in its current form, represents a future existential threat to the city and its residents.
The two models that were developed respond to the specific needs of the context and were tested in stakeholder meetings with house owners, local structural and heritage experts, the municipal council, and the national buildings department. The analysis of the design prototype indicates improvements from existing housebuilding in terms of embodied carbon, spatial efficiency and natural ventilation, as well as creating a system that is affordable for residents and within the existing skill set of construction workers.
The Core House proved to be less suitable for inner heritage core areas in terms of both the size of available plots—most were less than the minimum required (5 × 5 m)—and its lightweight cladding system which did not meet the approval of heritage experts as it was not brick. Instead, the Core House has a more appropriate application at sites on the edge of historic zones, where plot sizes are larger and the need to comply with material uniformity is more relaxed. Currently, in these areas the development trend is for the house to sit within a walled plot to create front and back yards. This erodes many of the characteristics of the traditional Newari settlement, e.g. the hierarchy of spaces from the public domain of the street to the private domain of the house which includes shared courtyards, connecting alleyways and raised front steps (Figure 9). Although cultural heritage discussions focus more on the aesthetics and objectification of the facade, the argument here is for increased consideration of the spatial relationships between the building blocks of the city—the house—and the connective urban fabric that it informs. Current typologies of housebuilding isolate themselves from their urban context, cutting out the possibility of hierarchies of public domain from the family to the community, to the district, to the city. As this was so well-calibrated in the spatial organisation of the Newari settlement, it should be a critical driver of how the future settlement evolves. The possibility of the Core House typology and its capacity to alleviate the ground for shops, alleyways or to become an open public space offers an alternative for these relationships between public and private to be articulated.
Figure 9
Comparison between the traditional urban fabric of the core to the edge of the city.
Source: Authors.
The Wall House typology offers a more viable alternative for residential construction in core historic areas. In comparison with concrete frame with an applied brick facade, it outperforms in terms of seismic resilience and environmental performance, and competes on affordability. It met with resistance from more conservative members of The Society of Nepalese Architects (SONA) based on the lack of articulation of the facade in relation to traditional elements of ornamentation.19 To overcome this, the proposal is to collaborate with experts from this group to develop the facade whilst maintaining the key structural logic and spatial organisation of the prototype. In effect, in the same way that the traditional Newari house could accommodate different levels of ornamental carving depending on the house owner’s financial status, this could be the same for the prototype. Those with additional capacity to pay for carved windows, balconies and brick specials could do so. However, this should not be a reason to prevent other, lower income families from accessing the key benefits of the prototype in terms of seismic and environmental performance.
The authors recognise that their current evaluations of the performance of the prototypes are based on digital estimations only and may incur a bias towards successful outcomes, therefore the critical next step is to build the Wall House pilot project and evaluate its performance after inhabitation, ideally conducted by an independent auditor with the help of Lumanti, a family was selected as being the most in need from the community participants. This was supported by the cooperative as the family of eight is seen by the community as the most in need. Like most Chyasal residents, they have inherited this home from their ancestors; however, as with many in the Shahi caste, the family members have struggled to find work, with two of the second-generation sons of working age struggling with drug and alcohol addiction, and the first-generation father having passed away 15 years previously.
The Wall House design will be further developed for the family’s specific plot, and architectural and structural drawings will be submitted to the Lalitpur Municipality. The objective is to complete construction by September 2026 as a demonstration pilot to evidence proof of performance and shift policy towards recognising and subsidising this model. If the project is accepted within policy guidelines and the project is scalable, it will offer a much-needed contribution to how settlements in Nepal can adapt to the evolving pressure of urbanisation and climate adaptation.
Notes
[2] The research team conducted an interview with Rojit in September 2022 about his experience with post-earthquake reconstruction.
[3] This figure is from the authors’ own consultation of construction experts during the initiation of the pilot project house.
[4] This information was learned through the authors’ initiation of the pilot project and other various meetings and workshops with municipal and national-level building policymakers.
[5] The surveys of these 15 buildings are available in the supplemental data online at: https://www.dropbox.com/scl/fo/zuwzbj332din4g567xw6x/AD_i1peJmEDc56r8THJkYBs?rlkey=8vk14axu7z6wzmr0qtzu0m0vx&dl=0. All the following supplemental data can also be found using the same link.
[7] See https://oneclicklca.com/.
[10] This information was received from the authors’ local partner organisation, Lumanti Support Group for Shelter, updated in August 2025. Lumanti is a close working partner with this cooperative.
ACKNOWLEDGEMENTS
The authors thank Buddha Shrestha (Kathmandu University); Dev Maharjan and Deepak Shrestha (Earthquake Safety Solutions—ESS); Lumanti Joshi, Shristina Shrestha and Basundhara Maharjan (Lumanti); and John Harkins (Prime Consulting, Hong Kong).
COMPETING INTERESTS
The authors have no competing interests to declare.
DATA ACCESSIBILITY
The relevant data are available at: https://www.dropbox.com/scl/fo/zuwzbj332din4g567xw6x/AD_i1peJmEDc56r8THJkYBs?rlkey=8vk14axu7z6wzmr0qtzu0m0vx&dl=0.
ETHICAL APPROVAL
Ethical approval was granted by the University of Hong Kong’s Human Research Ethics Committee (reference number EA220025).