Building with Sandstone
Desk Research & Primary Findings
Issued on: 30th August 2023
1. Background on Sandstone
1.1. Overview of Sandstone
Sandstone is a type of sedimentary rock that can be found in abundant quantities on the Earth’s surface (Hall, 2010). It has been used as a building material since ancient times and continues to be a popular choice for traditional Lesotho houses, as noted by Piotr (2021). The use of sandstone as a construction material dates back to approximately 1825 circa the founding of Lesotho and the reign of the country’s first King Moshoeshoe I. Traditionally, small round houses called ‘rondavels’, were built from sandstone by the Basotho people as shown in Figure 1.
In recent years sandstone has become popular in Lesotho as a building material for prestigious hotels, lodges, as well as institutional and government buildings themed along vernacular designs. Despite the popularity of the building material, various factors have led to a decline in the usage of sandstone in the present architectural and construction era. These include financial, technological, and logistics-related challenges. The primary challenge remains the procurement and sale of the material for homeowners. The perception among Basotho is that dressed and cut sandstone is prohibitively expensive and is only affordable to wealthy households, due to the misconception that its mineral-like qualities make it expensive. Furthermore, despite the emergence of more advanced construction techniques in Southern Africa, the potentially lucrative natural building material in Lesotho has remained untapped at an industrial level (Bourne, 1982). These can still be seen in various parts of the country, but architectural development has produced modern buildings that take advantage of the materials’ various properties and abundance.
The literature reviewed about sandstone did not explore the possibility of utilising it on an industrial scale in Lesotho. There are socioeconomic, political, and environmental factors associated with the usage of sandstone in widespread construction. These take into consideration its availability, accessibility, durability, carbon emissions, and environmental impact. This research will specifically address these issues.
1.2. Geomorphology of Sandstone in Lesotho
Hanco (2004) states that the Karoo Supergroup rock underlies Lesotho, consisting of sediments and basaltic lavas. The sandstone sediments in this region are classified into three types: Clarens, Elliot, and Molteno (refer to Fig 2). As a result, there is a consistent underlying geology in Lesotho, and each geomorphological unit contains a distinct sandstone type (Davide, Katrin, & Julie, 2020). The various formations have resulted in diverse sandstone types being distributed throughout the region, each with its unique characteristics. Moreover, the local climate and environment significantly impact the sandstone types found in different areas, which means that different types of sandstone can be present in one location.
1.3. Sandstone Formations
The Clarens Formation is spread across a vast area in the central highlands of all provinces in the Republic of South Africa and in different regions of Lesotho, both in the lowlands and highlands. Various sandstone deposits from the Clarens Formation can be found in Lesotho, but the largest mining area that has been utilised is in the Berea District, specifically in an area called Lekokoaneng, which is regarded as the largest quarry in Southern Africa (Eriksson, 1981). (see Figure 3.1 & 3.2)
The unit is situated stratigraphically between the red beds of the Elliot Formation. The thickness of the Clarens Formation is usually between 115 m and 195 m, and it consists of light-colored, fine-grained sandstones, sandy siltstones, and mudstones, as well as subordinate coarser-grained components (Eriksson, 1981). The rock’s surface is white when first extracted from boreholes and quarries, but when exposed to the elements, it weathers to a characteristic tan or golden hue. Due to its very low permeability, the rock is an ideal building material. ( see Figure 4.1 & 4.2)
The Elliot Formation is present in multiple locations in Lesotho, including Qacha’s Nek, Quthing, and near the capital city of Maseru, particularly in Nazareth. This formation varies in thickness, ranging from 28 metres to over 150 metres, and consists of red-coloured, clayey sandstone with a grain size that varies from fine to coarse and gritty at the base (Eriksson, 1985).
The thickness of the Molteno Formation varies between less than 10 m and more than 100 m, making them less permeable and it is composed of grey mudstone, shale, and sporadic coal seams. The sandstones in the Molteno Formation may range from fine to very coarse and are primarily composed of quartz-rich feldspathic wackes. They have high interstitial content and may exhibit subordinate argillaceous structures, according to Eriksson (1984). The sandstone from Clarens and Elliot is not permeable and has a low chance of aquifers, but Molteno is more permeable and is regarded with a high chance of aquifers occurring.
2. Advantages of Sandstone
Sandstone is an essential and sustainable building material that boasts remarkable longevity and durability (Kristensen, 2016). It also has a significantly lower carbon footprint compared to other widely used building materials. The carbon emissions associated with mining and processing are minimal as it does not require high energy consumption to extract. The amount of waste generated is also minimal in contrast to the production processes involved in creating prominent materials like concrete bricks (Kristensen, 2016).
According to Kristensen (2016), building with sandstone offers significant long-term cost savings that outweigh the initial higher material costs. This is due to the fact that sandstone buildings can be easily redeveloped, adapted for change in use, or remodelled internally without having to buy replacement materials. Sandstone buildings also have a longer serviceable life than their design life, and at the end of their useful life, they can be recycled in various ways.
According to Kristensen (2016), using sandstone in construction can significantly decrease energy consumption compared to lightweight concrete blocks. This is because sandstone can absorb heat during the day and release it at night, helping to maintain ambient local temperatures. Sandstone’s chromatic variation enables it to be used for various purposes. The material is often used in the restoration of historical buildings and monuments due to its availability and compatibility with traditional building materials. Since sandstone doesn’t require any specialised cleaning techniques, it is relatively easy to maintain. It can also be coated with anti-graffiti and self-cleaning materials. It is often utilised outdoors and typically has high resistance to moisture and harsh weather conditions, as stated by Grab (2010).
The main disadvantage exhibited by sandstone is the presence of different types of matrix that can affect the various properties. A small amount of carbonate in the matrix, for example, can dramatically decrease resistance to rain effects. Many sandstones contain small amounts of clay minerals, which are often inert but can sometimes swell, leading to damage under persistent wetting and drying cycles. In some instances, clay-rich inclusions or zones weather rapidly. Frost attacks will be a major factor in Lesotho. Cycles of heating and cooling will also gradually flake the stone surface (Hunt,2019).
In addition, the drawbacks of sandstone are a consequence of the material it’s made from, particularly from the Clarens formation called Lesehloa. For example, sandstone is known for being porous and therefore has a high absorption rate which makes it vulnerable to damage with time. In extreme cases, liquid, moulds, and bacteria can cause permanent stains deep into the stone. Having said that, certain types of sandstone may not be aesthetically pleasing (Grab, 2010).
Due to the relatively hard nature of the rock, the blade of the machine used for extraction wears out quickly after 3 days, necessitating frequent replacement. Additionally, a significant amount of water is required to wet the rock for the blade to pass through.However these advantages are minimal and surmountable, and there are enough advantages that outweigh the disadvantages to make sandstone a viable building material to research further.
There are economic factors related to the use of alternatives to sandstone in regards to the development of the mining and construction industries in Lesotho. These include human resources lost to neighbouring South Africa in search of employment. Additionally, there are costs related to the transportation and production of alternative building materials. There is an opportunity cost due to the lack of development of the sandstone industry from a mining, logistics, marketing, sales, and construction perspective. Lastly, at a fiscal level, there is a balance sheet imbalance due to the importation of building materials that are not found in Lesotho.
Additionally, there are environmental considerations as to why sandstone may be preferred to alternatives in the building industry. Often with these, time becomes a significant factor because of the inherent climate change, ecosystem, and sociopolitical impacts that may occur later. Local production of sandstone has the significant advantage of imposing a lower embodied and operational carbon footprint. Lastly, the deconstruction of sandstone buildings yields little-to-no additional waste due to it being a naturally occurring and eroding material. However, quarrying has a permanent impact on the geography and ecosystems around the mines. The silt formed also travels via wind and water causing adverse weather and ecological changes.
There are sociopolitical issues to be thought of when considering sandstone. For every mining plan, there should be proper vetting of the social impact on the existing and surrounding communities due to the industrial set-up. Community redeployment, pollution, and other public health concerns related to the geological and social changes must be rigorously assessed.
To collect primary data, stratified and snowball sampling were convenient techniques for this study. It was imperative to undertake interviews with professionals and experts with over 10 years of experience, knowledge, and skills working with sandstone. This chapter presents a total of 10 interviews conducted from January to June 2023, the researchers conducted face-to-face interviews that lasted between 45 minutes to 1 hour each. Qualitative surveys (see here for the Research Questionnaire) were used to gain in-depth information, experiences, and narratives about some specific topics such as availability, accessibility, cost, durability, and environmental impact of extraction.
The responses on the availability of sandstone allowed for a more generalised understanding of the geomorphology of Lesotho, potential areas for sandstone to be explored, quality, and existing quarries. Eight of the Respondents indicated that Lesotho is rich in sandstone and has the potential for large-scale mining. However, the Respondents stated that so far Berea district is the only area in the country that is mined with about five quarries, and one of the mines in that area is said to be the largest sandstone quarry in Southern Africa. The Respondents outlined that it is the only district being mined because of the belief that it has the best sandstone in the country that comes from the Clarens formation. Also, the Respondents further claimed that due to financial constraints, the Ministry of Mining has not mapped out areas of sandstone deposits. Instead, it offers individual maps that only highlight the geomorphology of Lesotho and do not pinpoint the exact areas where the deposits is found making it hard for individuals to venture out into the unknown without proper guidance and knowledge from the Ministry, showing the exact areas to mine in a particular district, hence certain areas like Quthing, Mafeteng, Letseng, and Mohale’s Hoek have not been explored. Nonetheless, the Respondents claimed that the 5 mines all have the potential to be mined at a vast proportion, which indicates that sandstone is available in abundance in Lesotho and more deposits of the material are yet to be explored.
In spite of that, two of the Respondents claimed that government policies and the environmental impact of mining of the material and encroachment of settlement play a big role in the availability of sandstone in the country. The Respondents stated that due to the extensive sandstone quarrying in Lekokoaneng over the years, it is possible that the mines in that district may not be able to sustain large-scale production in the future or may be forced to halt operations to prevent environmental issues. Having said that, different approaches can be taken for the availability of the material such as resettlement of households and exploration of other areas with sandstone deposits.
The responses acquired on sandstone permitted for better understanding of the impact of the cost of extraction on the price of the material in comparison to conventional building materials. One Respondent narrated that the machinery, and extraction process have resulted in the material being a bit expensive. The Respondents claimed that the elements that lead to the buying price being expensive start from the acquisition of the machinery which has to be designed by engineers and imported from China. The Respondents outlined that during the extraction process, more labour and transport are required from the extraction phase, cutting, and polishing of the machinery according to the customer requirements. Lastly, disposing of clay, cut-off alongside transporting the final product to the storage warehouse contributes to the overall operational costs.
Additionally, the Respondents stated that the blade costs M15,000 ( EUR 724.65) and it is replaced after every 3 days and it has to be bought from South Africa. The Respondents further indicated that all these underlying factors have resulted in the buying prices being a bit higher as compared to other conventional materials, in that one block of sandstone that is the same size as concrete block type 6k costs M18.24 (EUR 0.91) making it a bit more expensive than concrete blocks which are M15.00 (EUR 0.75). Also in comparison to the cost of a manufactured clay brick, which in Lesotho is only manufactured by one state-owned factory called Loti, sandstone proves to be a bit more expensive as a clay brick costs M6.00 (EUR 0.30), and the equivalent sandstone size brick costs M7.93 (EUR 0.40). Additionally, due to the fact that the quarries are far from the general market, transport costs are expensive to bring sandstone to market.
Nonetheless, there are savings to be made in the long term. Given the durability of the material it does not require regular maintenance, no plastering is required, and given its thermal properties, savings in heating solutions during the winter are notable. There is a low likelihood of getting damaged due to the fact that it is less permeable than conventional material, reducing the costs of regular maintenance. The Respondents gave a clear cost-benefit analysis for both short and long-term costs of Sandstone, demonstrating that it is clearly a viable and feasible building material in Lesotho.
The respondents indicated that the formation of the stone plays a big role in its lifespan as this determines the strength and permeability of the material. All the respondents agreed that the durability of sandstone is determined by the underlying formation indicating that the deeper the extraction process the weaker the stone, because of underground water, which results in it being more permeable, however policies put in place don’t allow extraction of rock to go lower than the surrounding area.
To determine the rock’s permeability, a viscosity test (porosity test) has to be carried out. The tests have shown that Lesehloa is highly permeable and breaks easily due to the fact that it is found underneath the lower Elliot and in the Molteno formation which is highly permeable and has high chances of aquifers. While Moramapholi comes from Clarens and Elliot formation, is highly durable due to its compact particles making it less permeable and the fact that it is found on top of the earth’s surface. All the respondents stated the underlying impact of the formation on the durability proving that Clarens and Elliot are highly durable.
Nine of the respondents pointed out that because the mines do not use blasting there is little environmental impact and pollution. Also after the extraction process, the material does not require treatment leading to low carbon emission. Since the extraction process requires a lot of water the quarries have built dams that allow water to circulate back into the plant reducing the amount of runoff water into rivers, which endangers the animals. Additionally, the licences from the Ministry of Environment and Mining permit 10 years of extraction which helps in evaluating the extent of the impact on the land and surrounding area.
However, one Respondent asserted that sandstone mining has negative impacts on the environment. This is because quarrying of the material changes the landscape, besides that runoff and groundwater from the mine goes into the water system leading to polluted water. Additionally, offcuts are haphazardly disposed of and there are no progressive rehabilitation preservation measures after the extraction is done. The government is failing to monitor the enforcement of regulations required to protect the environment. Nonetheless, with proper monitoring environmental impacts can be avoided.
Lesotho has 5 sandstone companies and more deposits to be explored. However, during an interview with the Ministry of Mining and Natural Resource, we were informed that the Ministry does not know how many sandstone deposits there are in Lesotho and there is no strategy put in place concerning the other deposits due to constraints in finances and labour as it is time-consuming.
There is an existing market in and outside of the country particularly in South Africa. The skillset is already available for extracting and polishing. The cost of extraction is expensive, particularly the machinery and the blades which are imported. Therefore, the companies need to be in a position to invest a minimum amount which depends on the type of machinery required. Respondents indicated that required start-up investment costs are about M300 000,000 (EUR 150,000) to be in a position to start up a sandstone mining business. However, the other companies stated that within 1 year they had already broken even and were making profits.
The 5 sandstone quarries in the country are the primary distributors, selling directly to customers in the country on demand and exporting the majority to wholesalers in SA with assuring access to the productivity of over 2,000,000 square metres of a natural resource from the mines. There is a need for quarries to establish partnerships with wholesalers and distributors in order for sandstone to be commercially available to consumers. It’s not a fragile material hence special transportation, packaging, and care are not needed.
Lesotho still hasn’t mapped out potential areas where sandstone can be mined, due to the fact that it’s time-consuming and financial resources are not available to map out potential areas other than in Lekokoaneng, hence there is insufficient knowledge of the country’s mineral resources endowment and mineral exploration is inadequate. There is an absence of strategies for developing industrial clusters and general economic diversification through infrastructure development and planned connectivity of the mining sector to other economic sectors such as manufacturing and wholesale companies. To fully leverage these benefits, there is a need for innovation in sandstone construction techniques, such as modular designs and prefabricated building components, to increase efficiency and reduce costs.
Sandstone as a building material has been disregarded mostly due to people’s preconceived idea that it’s expensive to buy sandstone as opposed to clay bricks or concrete blocks and failing to see the long-term economic and environmental benefits of using sandstone. Additionally, the lack of knowledge with regard to areas in which it is available in the country has led to a small exploration of extracting sandstone when it could be done at a large scale. Therefore, this has led to the apparent shift to readily available modern building materials such as concrete blocks. Hence, there is an opportunity to revive this vernacular material and promote its benefits and its ability to be more sustainable and environmentally friendly than modern building materials. Sandstone from its extraction and processing has the lowest carbon emission compared to other conventional materials such as concrete blocks. Additionally, a framework was created in (The Minerals & Mining Policy of 2015) that works towards mitigating the negative impacts that occur during the mining of the sandstone, hence making it more sustainable compared to other building materials. Furthermore, its thermal properties result in lowering the amount of high-carbon fossil fuels used to heat the buildings, offering both economic and environmental long-term benefits.
More research needs to be done on the country’s mineral resources endowment. Geological mapping and mineral exploration need to be commissioned by the government. This requires resources and proper planning. This is beyond the scope of our work, however, we will sensitise the Government of Lesotho within their strategy for economic development and trade. Strategies for developing industrial clusters and connectivity of the mining sector to other economic sectors such as manufacturing and wholesale companies. There should be investments in proper advanced machinery. Also, rather than the ministry just renewing licenses every ten years for companies, the ministries must know the number of years that sandstone can be mined in a particular area and make sure that all regulations are followed to avoid environmental damage.
There is also a need to look into the life-cycle cost of mining and processing sandstone for use in the built industry. This will promote a fair assessment of the overall health and environmental benefits of using sandstone over conventional construction material.
Appendix A: Table of Respondents
|Name of Company/Profession
|Number of years of Experience
|Profession /Qualifying Criteria
|Lesotho Leading sandstone
|Ministry of Mining
|Ministry of Environment
|Craftsman and sandstone supplier
|Craftsman and sandstone supplier
|Likhalakhala lia buseletsa
|Craftsman and sandstone supplier
|Kou sandstone company
|Director and owner
|Lerotholi Sons and sandstone suppliers
|Sandstone mining Lesotho
Academic Accelerator . Elliot Formation. https://academic-accelerator.com/encyclopedia/elliot-formation. (Accessed: 12/01/2023)
Davide, G., Katri, W. & Desarnaud. J. ( 2020). Integrated Strategy to Assess Conservation Treatments on Sandstone.https://www.tandfonline.com/doi/pdf/10.1080/00393630.2020.1767332. (Accessed: 12/01/2023)
Eriksson, P.G. (1981). A palaeoenvironmental analysis of the Clarens Formation in the Natal Drakensberg. Transactions of the Geological Society of South Africa , 84:7-17.
Grab,S. & Goudie, S. A. (2011). Sandstone geomorphology of the Golden Gate Highlands National Park South Africa in the global context. https://www.researchgate.net/publication/262701314_Sandstone_geomorphology_of_the_Golden_Gate_Highlands_National_Park_South_Africa_in_a_global_context. (Accessed: 12/01/2023)
Hanco, J., Rubidge, B. & Bordy, E. 2004. A Description of the Sedimentology and Palaeontology of the Late Triassic–Early Jurassic Elliot Formation in Lesotho.
https://www.researchgate.net/publication/239521319_A_description_of_the_sedimentology_and_palaeontoloy_of_the_Late_Triassic-Early_Jurassic_Elliot_Formation_in_Lesotho. (Accessed: 15/01/2023)
Hall, S. & Hughes,D. (2010). Local characterisation of fluid of flow in sandstone with localised deformation features through fast neutron imaging. https://portal.research.lu.se/en/publications/local-characterisation-of-fluid-flow-in-sandstone-with-localised-. (Accessed: 15/01/2023)
Hunt, B. 2019. Building Stones Explained. https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1365-2451.2008.00649.x. (Accessed: 12/01/2023)
Kristessen,T. & Wogwitka, R. J. (2016). Beaver River Sandstone: A silicified toolstone from northeast Alberta Canada. https://www.researchgate.net/publication/311824467_Beaver_River_Sandstone_A_silicified_toolstone_from_northeast_Alberta_Canada. (Accessed: 13/01/2023)
National Geographic Society (2022). Sedimentary Rocks. https://education.nationalgeographic.org/resource/sedimentary-rock/. (Accessed: 13/01/2023)
Palaeo Electronica. Geological Background of the Clarens Formation. https://palaeo-electronica.org/2008_3/150/intro.htm. (Accessed: 12/01/2023)
Piotr. M. (2021). Sandstone geomorphology – Recent advances. https://www.sciencedirect.com/science/article/abs/pii/S0169555X20304578. (Accessed: 13/01/2023)
Sphera (2020). What is Life Cycle Assessment? https://sphera.com/glossary/what-is-a-life-cycle-assessment-lca/. (Accessed: 15/01/2023)