Examining change and permanence in traditional earthen construction and preservation in Ghana: A case study of Tamale and Wa

The architectural style found in Wa and Tamale is renowned for its distinctive use of earthen construction, featuring square buildings with flat roofs and circular compounds with conical thatch roofs. These structures represent a significant evolution in both materials and design in northern Ghana. What are the driving forces behind the changes in cob construction in this region? Furthermore, what potential impact might these changes have on preserving cultural heritage in Ghana? This study adopts a pragmatic research approach to explore the factors contributing to the departure from traditional earthen building methods that rely on local materials. Instead, there is a growing inclination towards alternative construction techniques that use non-traditional materials like cement, bitumen, and used car engine oil to render wall surfaces. Additionally, using sun-dried bricks alters the structure and compromises the resilience of buildings. While most respondents have resided in buildings rendered with a mixture of beini and dawadawa, they are hesitant to use plant-based bio stabilisers in recent construction. The hindrances to the ongoing construction and preservation of earthen buildings encompass shifting cultural and social norms, environmental changes, difficulties accessing local building resources, flood risks, regular maintenance requirements, and societal influences. The study concludes that by empowering the community to take ownership and recognise the value of their cultural heritage, there is a likelihood of increasing awareness and appreciation of the architectural heritage within the local community, ultimately leading to its preservatio

Bio-stabilising earthen houses with tannins from locally available resources

This study presents the first-ever comparative evaluation of traditional biostabilisation practices for housing employed in Northern Ghana. Such a comparative evaluation is crucial in understanding and addressing the increased risk of flooding in the region due to a combination of climate change and land use changes. Given the environmental conditions and material availability that shape construction techniques in this area, it is imperative to assess the effectiveness of these practices in mitigating flood risks. The investigation focuses on readily available resources from the Wa and Tamale regions, specifically dawadawa (D), beini (B), and rice husk (R). These biostabilisers were subjected to rigorous testing to assess their efficacy. Earth mortar samples were created using sieved plain local soil (P) with or without the addition of rice husk, which is a local practice, and dawadawa and beini solutions were tested as a water replacement (+wD or +wB, added during material manufacture) or as a surface cover (+coverD or +coverB). The effects are examined in terms of microstructure modifications detected through tannins type and presence, SEM/EDS, water absorption via capillary uptake, and compressive and flexural strength for two different types of application: embedded in the mixture or covering the surface. Overall, solutions containing dawadawa were superior to those containing beini for the tested soil. Both coverD and +coverB decreased the water absorption capacity of the earth mortars and provided almost complete protection for 15 minutes. After three days, all mortars mixed with the dawadawa or beini solutions (P+wD, PR+wD and PR+wB) displayed lower absorption than the P material. Condensed tannins were identified in dawadawa, but only small precipitation in beini and no precipitation in the rice husk. This indicates that dawadawa has a greater degree of polymerisation (compared to rice and beini), developing a polymerisation tannin-iron complex in contact with oxygen from the air, which explains the macrostructure results. SEM/EDS results indicated polymeric condensed tannins and hydrolysable tannins and that complex accumulation and subsequent oxidation are the main reasons for improving water resistance. The laboratory tests, therefore, support the traditional methods of using dawadawa, beini, and, to a lesser extent, rice husk to improve the resilience of earthen houses and structures to water damage and can be used to encourage agro-industry in Northern Ghana to preserve and promote dawadawa and beini resources

Fragility Assessment of Traditional Wooden Houses in Madagascar Subjected to Extreme Wind Loads

Cyclones are a common hazard in Madagascar, each year causing fatalities and damage to the physical and socioeconomic infrastructure. Residential infrastructures are a critical sector within the built environment and studying their performance under natural hazards is a significant step for assessing the risk and resilience of a community. In the coastal regions of Madagascar, more than 80% of houses are self-built, non-engineered traditional wooden houses constructed based on heritage practices and using low or no-cost materials collected in nearby areas or forests. These traditional wooden houses are particularly vulnerable to cyclonic winds and, in this paper, a novel approach is used to evaluate their structural performance and to predict their likelihood of failure under extreme wind conditions. The structural systems and their damage due to extreme winds were first evaluated based on field surveys and collected information such as post-disaster reports. A range of field tests was then carried out at two coastal sites to evaluate the strength of the members and connections identified as commonly used for constructing traditional wooden houses in Madagascar. Damage fragility curves were subsequently developed based on the performance of the connections of roof coverings, wall claddings, the roof structural system, and the performance of columns embedded into the ground and combined to predict the structure's performance. The experimental methods and results presented in this study can be exploited to improve the existing Malagasy guidelines for cyclone resistance of traditional wooden houses published in 2016. The developed fragility curves can also be used to represent traditional wooden houses within a community for risk or resilience assessment under cyclonic wind conditions

Assessing South Indian Ocean tropical cyclone characteristics in HighResMIP simulations

Several damaging tropical cyclones (TCs) have occurred recently over the South Indian Ocean (SIO) region, causing enormous social and economic losses. Yet, while many studies have examined SIO TC characteristics using observations and reanalysis, only a few have assessed these characteristics specifically for this region in climate models, and fewer have investigated their projections under climate change. Here we do this for a historical (1980-2010) and future (2020-2050) period, using multi-model simulations from the High Resolution Model Intercomparison Project, as well as examine biases in the historical period relative to a reanalysis (ERA5). The models have horizontal resolutions of 25-50 km, which has enabled an improved ability to represent tropical cyclones globally in previous studies. TempestExtremes software is employed to detect tropical storm and cyclone tracks. In cases where TempestExtremes cannot be applied due to a lack of requisite variables in a dataset, we instead examine extreme wind speeds in that dataset. For the historical period, we find considerable variation in model biases compared to ERA5, which itself exhibits realistic spatial patterns of tracks and their monthly distribution. Models do at least agree on positive biases in track frequency east of Madagascar and somewhat in the Mozambique Channel. However, the models and ERA5 only produce category 3 tropical cyclones at best. Wind speeds for 25km resolution models have much larger positive biases than for 50km ones, suggesting the former can simulate even higher-category tropical cyclones. Considerable inter-model variation is also found in track changes between the future and historical periods. No systematic inter-category pattern of change exists, and low signal-to-noise may obscure any such patterns in the limited timespan of available data. Thus, no meaningful conclusions can be drawn regarding changes in track intensity. Nevertheless, track frequency broadly decreases across models for the region, as does accumulated cyclone energy. An east-to-west shift in track location from east of Madagascar toward the Mozambique Channel is also implied by track frequency and wind speed changes. Our findings provide information to potentially improve storm resiliency in this vulnerable region

Strength and durability of biostabilised Ghanaian mud bricks

Communities in northern Ghana (Tamale and Wa) rely on earthen materials to construct affordable houses. However, these traditional practices are threatened by climate change: repeated flooding is triggering a transition to using cement-based building materials, and urban expansion and loss of biodiversity threaten the source of biostabilisers traditionally used to protect structures from water damage. Local builders currently rely on cementitious or bituminous renders to protect earthen houses, but these can trap water within the walls and so increase the likelihood of failure instead of protecting the buildings from harm. Such materials are, however, viewed as being prestigious and local people race to be able to apply them to their homes, creating a vicious cycle of earthen building degradation. This paper explores the possibility of using traditional Ghanaian biostabilisers dawadawa and beini in communities in northern Ghana to create water-resistant earth renders, to stabilise earth bricks and avoid the need for cement or bitumen. Methods used in Tamale and Wa to manufacture mud bricks were identified through field studies and used to recreate specimens in UK laboratories. The compressive strength and resistance to water (from immersion or dripping water) were tested for unstabilised bricks and bricks stabilised with a solution of dawadawa or beini. The results indicate that dawadawa can quadruple the resistance of mud bricks to water damage for no loss in mechanical properties, creating a strong incentive to protect and manage this resource