Earthen Architectural Heritage in the Gourara Region of Algeria: Building Typology, Materials, and Techniques

Abstract

This article investigates the status of earthen architectural heritage (EAH) in the Gourara region of Algeria in light of contemporary developments and the sovereign decisions taken by the Algerian state, specifically the upgrading of the region to a wilaya (province) in 2019, and the accompanying direct impact on the oasis system, which is renowned for its fragile character. The research started by focusing on perplexing questions: What factors contribute to the region’s abandonment of earthen architecture? Moreover, could documentation serve as the optimal method for its preservation? In an attempt to explore and comprehend this distinctive heritage, characterized by its diversity, durability, and sustainability, this heritage has been linked to identity and local civilization dating back to prehistoric times, with evidence of their existence still present. Following a research approach and with the prospective purpose of preserving these buildings and what remains of them, the associated skills, materials, and construction techniques used in their development were investigated based on a descriptive, analytical, and documentary historical approach. Finally, the authors interviewed several qualified builders to collect knowledge of the local indigenous building practices. The research findings suggest that there is an urgency to consider a new perspective and strategies to preserve and protect EAH.

1. Introduction

Earthen construction techniques have been utilized for millennia, with approximately one-third of the global population still residing in earthen buildings [1]. Much research proves how cultural, climatic, and geographical factors influenced the use of vernacular materials and technologies in earthen architecture worldwide [2]. In challenging natural conditions, earthen buildings are considered an extension of the earth’s planet, affirming the spiritual connection between humans and the earthen material [3].

In the last few years, there has been increased research on preserving earthen architecture in many countries, which can be summarized in four main axes: (1) information on cultural heritages, which includes identifying age [4], evaluating cultural heritage values [5,6,7], studying materials and examining structures [8,9,10], and applying conservation theory [11,12]; (2) protecting cultural heritage, which includes predicting the impact of natural disasters [13] and heritage recording via virtual reality [14]; (3) managing cultural heritages, which includes digitally identifying cultural heritages [15] and managing cultural heritages [16,17,18]; and (4) reusing cultural heritage, which includes cultural tourism through social media [19]. Several institutions pioneered earthen heritage preservation, including the International Center for Earthen Construction CRATerre-EAG [20], the Getty Conservation Institute [21], and the International Centre for the Study of the Preservation and Restoration of Cultural Property [22], which played a significant role in introducing EAH and scientific methods for preserving it.

Using the earth as a building material presents significant advantages [23], such as resistance to fire, availability, recyclability, embodied energy, and thermal capacity; in another way, the disadvantage is that it is not standardized, it is costly, has no codes and policies, and has susceptibility to physical degradation, mainly due to its vulnerability to water. In this regard, much research has been conducted on the subject [9]. However, several local strategies can help mitigate these issues, including roof design, quality of dressing, and foundations.

As a building material, earth dates back to ancient times, where the oldest earthen buildings are circular dwellings carved into the ground at the two archaeological sites in Aïn Mallaha and Hayonim in Jericho, Palestine. This building material dates back to the final Epipaleolithic period, which marks the beginning of the Neolithic period, from the middle of 13 thousand to 10 thousand BCE [24]. This technology soon spread to the Near East (including Jordan, Syria, Iraq, Iran, and Turkey) and then to various regions throughout history, especially with the emergence of human populations [25].

As a material, earth (soil) results from transforming the underlying parent rock under the influence of various physical, chemical, and biological processes linked to bioclimatic conditions and animal and plant life [1]. Clay is the main component of brick adobe. It is documented that adobe techniques have remained similar across different civilizations from ancient times to the present [1,26]. However, the process varies in nuances from region to region [27], and it is influenced by acquired skills, the type and quality of clay, additives and stabilizers, and mold shape and size. On the other hand, due to the widespread use of earth in all stages and parts of construction, clay maceration is considered mandatory for its durability. Without this, earthen buildings become less durable and more susceptible to natural and human factors. From a technical standpoint, maceration alters the crystalline structure of the clay and saturates it with water, contributing to the durability of earthen buildings.

Earthen architecture in the Gourara region (Algeria) is part of the oasis system. It is distinguished by the use of locally available materials, its simplicity, and lack of complexity, but it is not devoid of aesthetic touches. The customs, traditions, and Islamic religion of the people in this region have led to earthen architecture without ostentatious displays [28].

Accordingly, with the decline of the oasis system [29] and the accompanying rupture of local building practices and associated skills, the concept of EAH and its preservation deteriorated and came to be viewed negatively and inferiorly [6]. In Gourara, it seems clear that the current situation of EAH demands an evaluation and reconsideration immediately, given its historical and architectural significance, lest it become too late; so, safeguarding EAH has become a shared human responsibility and should be prioritized by the Algerian state exclusively in light of contemporary developments.

The problem of preserving EAH in Gourara lies mainly in two reasons, which many different researchers frequently refer to in a related and overlapping context [23,30], and they are mainly manifested as follows:

-

There is a lack of familiarity with earthen architecture and the accumulated mystery surrounding the factors affecting the acceptance of earthen architecture [23]. Jean-Claud Morel identified at least sixty barriers to using earth as construction materials [31]; they were divided into six groups (economic, organizational, sociological, political, technical, and environmental).

-

There is a misreading and misunderstanding of the laws related to heritage. Algerian laws encourage heritage protection, starting with the highest legislation, the 2020 Constitution, in which Article 76 indicates that “The State protects the national tangible and intangible cultural heritage and works to safeguard it” [32]. Further, law No. 98-04, Article 08, relating to the protection of cultural heritage, states the following [33]: “Real estate cultural property that includes historical monuments, archaeological sites, and urban or rural groups is subject to the protection regime, which can be registered in the additional inventory list, classification, or creation of save sectors”. Thus, confusion occurs about real estate cultural property that is not subject to the mentioned protective regime but submission to Article 38: “Spaces that are characterized by a predominance of cultural property and that are inseparable from their natural surroundings are classified as a cultural park”.

On the other hand, the real challenge in protecting the EAH after the upgrading of the region to a wilaya [34] lies in how the power of the wilaya is used to address and deal with EAH. As stated in Article 17, “The local authorities of the state are the municipal and the wilaya” of the 2020 Constitution [32]. Amid the establishment and reinforcement of new administrative infrastructure [6], responding to the aspirations of citizens, including providing employment, housing, and various life requirements, and keeping pace with the laws of the Republic, greatly depends on the new wilaya’s approach to preserving EAH.

To understand this overlapping situation, it is possible to briefly comprehend the real reasons behind the abandonment of earthen buildings, such as the decline of the oasis system and its consequences, to remove the confusion about the extent to which earthen architecture is acceptable. The documentation of EAH is relied upon to contribute to alleviating confusion regarding the preservation and promotion of EAH in light of national legislation.

By inventorying significant techniques and materials of earthen architecture, we seek to conserve the region’s EAH while potentially adding to a sense of national and local identity. Then, this inventory can to be used by the local authorities and for every helpful purpose.

2. The Context of Study

2.1. The Location of the Study Region

The Gourara region is located in the southwestern part of the Algerian desert. It is currently known as Timimoun’s wilaya (province), and its headquarters are in the same city. Geographically, the region is bordered to the north and west by the Grand Erg Occidental, to the east by the Tademait plateau and M’Guiden (an ancient pastoral area), and to the south by the Touat region (Adrar). It is located between the latitudes 31°30′ to 28°30′ north and the longitudes 1° east and 2° west of the Greenwich line [35].

The region’s location forms a large triangle, where the northern side plunges deeply into the Grand Erg Occidental, and the western side stretches far across the Tademait plateau; so, only the area in the southwest corner is genuinely alive (Figure 1).

2.2. Historical Background of Gourara

According to R. Bellil [36], the history of Gourara can be summarized into three distinct periods; the first one predates the 15th century AD when Gourara was formed of isolated fortified granaries, which are locally called “Agham” (plural “Ighamawen”). The second period saw the coming of Saint Sidi Moussa and the creation of a market called Souk Sidi Moussa in Timimoun. The market’s creation attracted the Ighamawen and facilitated the construction of the current historical city of Timimoun. The third period marked French colonization, dating to 26 May 1900, when the troops from El Golea under the command of Colonel Ménestrel then joined with the column of Commander Letulle [35]. Many exploratory campaigns [37,38], such as the missions of Eugène Daumas (1835), De Colombe (1856), and Flamand (1889), preceded the region’s French presence.

2.3. Meteorological Conditions

2.3.1. Temperature

The region is characterized by significant differences in daily temperatures between day and night and seasonal differences between winter and summer (Figure 2). The highest rate recorded (2003–2023) reached 47.8° during July 2018, a difference of 15.6° between the lowest and highest rates for the same month. Its lowest average was 2.9° in January 2005 [39].

2.3.2. Winds

The region’s location within the trade wind zone, which is characterized by strong winds, increases the harshness and instability of the climate [40]. These winds contribute to the carving of rocks and the erosion of the earth’s surface, which helps gradually form sand dunes. According to the wind records below [39], the wind rose over the region from January to March, with its direction changing to become easterly, beginning in April, reaching its peak in July, then changing to easterly winds during November and December. These records show the dominance of northeasterly winds (Figure 3).

The southwesterly winds are observed blowing throughout the months of the year, with their intensification during the months of April, May, and June.

Sand-laden southeasterly winds blow throughout the year, intensifying during June, July, August, and September. These winds significantly change the morphology of the earth’s surface. If they are not dealt with by traditional methods, locally called “Afrag”, which involve the construction of a wall of palm tree blades connected with a braid of the same wall material, sand encroachment on the entire oasis may occur. Evidence of sand encroachment in the region was found at Tgaza in Badrian, Timimoun (Figure 4).

2.3.3. Humidity

The highest percentage of humidity is recorded inside the oasis between the palm groves, under the influence of irrigation water, so the humidity is somewhat high. The humidity recorded between 2019 and 2023 in the airports of Timimoun [39] differs from this, reaching its maximum level in December (2021) at 67.9% and falling to its lowest level in July of the same year at 8.48% (Figure 5).

2.3.4. Precipitation

Precipitation from 2003 to 2023 reached a maximum height of 69.3 mm in 2004 [39] (Figure 6), causing the region’s valleys to flow and producing severe damage to the oases of the region. It was then known as the 2004 flood, which was the final turning point for earthen architecture; in other words, it was the irreversible, decisive event for the residents of the region to return to earthen architecture, especially with the official manner adopted by the local authorities during the event. What is puzzling is that the flow of valleys and the occurrence of calamities in the region were not new events. It occurred in October 1950, 1992, and 1999 [28]. In 1950, the height of the falling water reached 21 mm for a period estimated at five continuous hours, causing severe damage to the valleys’ flow [35].

2.4. Geological Setting

Much research has focused on the region’s geological studies, especially in the context of petroleum and gas research and exploration. The National Agency for the Valorization of Hydrocarbon Resources, “ALNAFT” [41], mentions the presence of the Mesozoic covering basins of Timimoun. At the base of the Mesozoic basins, Triassic sandstone reservoirs, which developed under a salt cover during the Triassic to Liasic age, constitute the elements of the petroleum system of the Hassi R’Mel deposits NE of Timimoun.

According to Nedjari and Ouali [42], the geology of Gourara combines the history of a basin described as Hercynian syneclisis, which is atypical because it is mobile, with that of a predominantly Mesozoic continental margin. His evidence comes from the following geomorphological sets (Figure 7): (1) a Devono-Carboniferous chain, (2) the continental intercalaire, (3) an upper Cretaceous site, (4) a continental terminal, and (5) the Grand Erg Occidental.

2.5. The Oasis System and Its Decline

2.5.1. Generalities

According to Marc Côte [43], the oasis is a remarkable human creation that acts as a bubble on the surface of the desert. When one element disappears, the others are annihilated. This system consists of the foggara, Ksar, and palm groves (Figure 8). The foggara, as a water source, is a slightly inclined underground gallery that drains water from the upstream aquifer toward the driest lands downstream (palm groves as a source of livelihood). It passes through the Ksar as a place to live, defined as a set of habitats with a structure gathered in one place. The structure of the Ksar appears simple, but the simplicity of its forms can hide the complexity of social organization.

The oasis system is governed by the local community system called “Al-jamāʿa” and is strictly subject to local customs called “Al-a’rf”. It has an independent judicial system that derives its sources from custom [44] and Islamic law.

Property (such as palm groves and real estate) and roles (such as the presidency, imamate, hard work, and trade) are distributed according to social stratification as a community organization. Social stratification was founded on lineage, prestige, skin color, and income, followed by the esteem, compassion, or contempt that people have for each other [45]. One of the unique features of the oasis system in Gourara is the practice of “Touiza”, a significant cultural and social practice that involves volunteer work and manifests in cleaning the foggara, building mosques, restoring buildings after calamities, or any social aspect that connects to the Ksar.

Figure 8. The oasis system at Beni Mahlal Timimoun [46].

Figure 8. The oasis system at Beni Mahlal Timimoun [46].

2.5.2. The Decline of the Oasis System

The collapse of the oasis system is the real reason for the decline in the attitudes toward earthen architecture, and the notion of preserving EAH. The collapse of this system, which lasted for hundreds of years, was preceded by some developments, including the following:

(a)

The transformations of social roles and systems (tribe, clan, family, and household), which were accompanied by changes in social practices [47].

(b)

The outbreak of the Algerian agricultural revolution in 1971 [48], which states the following:

• Article 1: Land belongs to those who serve it, and only those who cultivate it have the right to land.
• Article 3: All exploitative trade for water resources intended for agriculture shall be abolished.
• Article 13: The provisions of this order apply to all agricultural lands, regardless of their real estate system.
• Article 28: The right of ownership in any agricultural land or land intended for agriculture whose owner does not exploit it shall be canceled.

Thus, two parts of the oasis system were radically compromised (foggara and the palm groves); so, the Ksar found itself alone in the bubble. The community system lost its role in managing this system, and the Constitution of the Republic replaced the customs.

Despite the abolition of the agricultural revolution in 1990, its obstacles continued to consume EAH for over 27 years; it was claimed that these obstacles were abolished in 2017 under the Finance Law of 2016. This stage overlapped with the deterioration of the security situation in Algeria, especially with the declaration of a state of emergency in 1992 [49], which extended for more than 19 years [50], where the dominance of local authorities over the urban and architectural landscape was known.

(c)

Reconsidering the EAH and its production, this period was characterized by the following:

• Due to stagnation that lasted for 43 years (1971–2014) and the fascination to which various media outlets contributed, and in light of the decline of volunteer work, concrete dominated the architectural and urban scene and the processes of intervention in heritage, without dispute, causing a deterioration of the EAH that had not been seen in centuries.
• Executive Decrees 14–27 were issued; these were related to the urban planning, architecture, and technique prescriptions applicable to construction in southern wilayas [51]. What is stated in Article 5 is especially noteworthy: “The prescriptions apply when the elaboration and revision of urban planning instruments and apply to the realization, transformation, extension, and renovation of all typologies of construction as well as space planning public in the municipalities of the southern wilayas”. There was hope of a new dawn for EAH. However, with the misreading of legislation, the situation soon paved the way for concrete buildings painted with the color of the earth and covered with earthen architectural elements under the name of the architectural production of EAH.
• The upgrading of the region to a wilaya (2019) raises another legislative concern about dealing with EAH, especially what is stated in Article 02: “The wilaya headquarters municipalities are excluded from applying the prescriptions contained in Executive Decree 14–27” [51]. This legislative omission may lead to the local authorities making wrong decisions regarding EAH.
• Petroleum discoveries in the region and their position on the priority scale of the country, which relies on hydrocarbons, were significant.
• This period concludes with issuing a legislative text related to the preservation and promotion of EAH, Executive Decree 23–401, which fixes the methods of preparing prescription books’ architectural features [52]. Article 6 states the following: “Local authorities prepare prescription books”. Further, Article 8 states the following: “The prescription books are prepared in two stages: diagnosis, such as identifying heritage characteristics and identifying extraneous and inconsistent elements”.

3. Materials and Methods

This work adapts the documentation methodologies used by many researchers to preserve heritage [53,54,55]. It is essential to admit that the proposed methodology relies exclusively on visual information to collect data related to building typology, materials, and techniques. The proposed methodology is designed around three steps, which are represented in Figure 9. The study was limited to visiting and documenting one-hundred and twenty-three Ksar, including twelve mosques, two retreats for worship, six Zawiyas, forty-nine mausoleums and shrines, and ninety-two Agham. The work was conducted according to the following stages:

Step 1: This step is preliminary work and involves the development of an initial understanding of the topic and knowledge of all possible stakeholders in the occurrence of causes contributing to the abandonment of earthen architecture, whether from near or far; it includes the following:

• Review of the literature on all aspects of EAH, including historical documents, cultural, human, and architectural values. It should be noted that most of what was recorded included military reports and human geography studies during the French occupation of the region.
• Access to all legal texts (official journal of the People’s Democratic Republic of Algeria) related to the protection of heritage, with knowledge of the authorities, their jurisdiction, and the relationship between them.
• Once the most critical aspects of the research are determined, the objectives are developed.
• Site visits, including escorts, seasons of the year, days of the week, times, and transportation methods, are planned.
• Data collection methods are defined, such as buildings positioned on a map and building codification.
• Data instrument tools are defined, such as laptops, cameras, camcorders, dictaphones, GPS, and notepads.
• A relationship is developed with the Algerian Centre for Cultural Heritage built in mud (CAPTERRE), and which is a public establishment created in 2012 under the Algerian Ministry of Culture and Arts guardianship. Its headquarters are in Timimoun, and its primary mission is to rehabilitate earthen architecture’s image by promoting and valorizing cultural heritage built on earth and the associated know-how [56]. Then, a list of qualified builders was obtained and checked; names, questions, and interview locations were defined.

Step 2: This step is fieldwork, and focuses on the following details:

• Visiting and documenting the buildings of the region.
• Becoming closer to local authorities and non-centralized directorates, such as the Directorate of Culture and Arts, the Directorate of Mujahideen and Rights Owners, and the Directorate of Urban Planning, Architecture, and Construction.
• Conducting two interviews with qualified builders and recording their experiences with earthen architecture and everything related.
• Data classification

Step 3: This is the data processing stage:

• Description of earthen building typologies.
• Description of earthen building materials.
• Description of earthen construction techniques.
• Description of the real reasons for the decline of these buildings.

4. Results

4.1. Earthen Building Typology in the Gourara Region

According to their function, buildings are divided into four categories.

4.1.1. Military Architecture

These are buildings with military fortifications, such as high walls, towers, loopholes, and trenches locally called “Ahfi”. Fortified granaries represent them. They may be completely isolated (Figure 10) or adjacent to the Ksar (Figure 8).

4.1.2. Civil Architecture

These buildings emerged later in the region’s lifespan, especially with the expansion beyond the walls of the Ighamawen (Figure 11), due to the establishment of security and stability in the area. This situation made it unnecessary to use military fortifications. These buildings include Ksours, (singular, Ksar), residential facilities such as markets, and public baths (like Bouh’di in Timimoun).

4.1.3. Religious Architecture

These buildings emerged alongside the spread of Islam in the region (Figure 12), including mosques, madrasas, Zawiyas, and Quranic schools. These buildings can be located in Ighamawen (such as mosques), in Ksar, or completely isolated, such as worship retreats.

4.1.4. Funerary Architecture

These are buildings associated with humans after their deaths (Figure 13), including facilities for washing the deceased’s body, outdoor prayer areas for funerals locally called “Al-maṣallá”, mausoleums locally called “Al-Darih”, and shrines locally called “Maqam” (tombs that do not contain any deceased).

4.2. Building Materials

The building materials used in the region have varied from one area to another and differed across different periods in their prevailing construction techniques and their local builders’ skills. These materials include the following.

4.2.1. Stones

According to texture, shape, and color (Figure 14), three distinct types of stones are used in the region:

(a)

Sandstone, locally called “Tafza”, is extracted from trenches or rocky plateaus where the Ighamawen is located and used for construction within the same context. At the same time, these grottoes (caves) are often used as summer dwellings.

(b)

Flat stones, locally called “Hajar Al-Safah”, are extracted from some rocky plateaus and limited locations. They were used to construct Ighamawen and cover the roofs of Muslim burial pits and their gravestones. Later, they began to be transported to the region’s capital (Timimoun) from the Ksar of Aghlad-Ouled Said, where their use became limited to decoration and funerary architecture.

(c)

Quartzite stones, locally called “Hajar Al-Sami”, which means deaf and nonporous stone, are known for their hardness and durability compared to the previous types. They were used in Ighamawen and are currently used mainly in construction. These stones are found in Hamada and on the plateau’s surface, like the Tademait plateau.

4.2.2. Clayey Soils

Clayey soils are usually found in nature in quarries close to the oasis or inside of it. They serve multiple purposes in construction, such as brick production, mortar, and plastering. The ease and simplicity of their preparation and the minimal effort required have facilitated their widespread use and mastery of techniques.

In Gourara, inhabitants distinguish between two types of clayey soils (Figure 15): the red range, which is used in all stages of construction and is distinguished by low plasticity, and the green range, which is rarely used in construction.

In some areas in Gourara (such as Talmine), clayey soil extraction is governed by constructive customs, which include determining the locations, allowed quantities, and extraction periods. The herald of the Ksar, locally called “Al-Barah”, predetermines and announces these customs, and any violations result in fines.

The preparation of these soils in Gourara involves a meticulous process. Initially, clayey soils are mixed with sand (brought by the wind and present in most spaces in the region’s buildings) in a dry state, followed by wet mixing with water. Additional materials, like wheat straw, can be incorporated into the mixture. The resulting clayey paste is left to dry, with periodic water additions to prevent hardening. This essential process is locally called “Al-takhmār”, or maceration, and the longer the maceration period, the longer the lifespan of the building.

4.2.3. Wood

Date palm wood is used in various building parts, including roofing, doors, staircases, wall reinforcement, locks, ropes, and permanent scaffolding. The following parts can be extracted from the date palm tree (Figure 16):

(a)

Trunk, locally called “Al-jada”, is a long, cylindrical, unbranched stem with a rough surface, petioles covering it, and a dense crown of big leaves at the top.

(b)

Fronds, similar to a huge feather, are the date palm’s leaves and consist of the following:

b.1

The blade, locally called “Al-Djerid”, refers to the upper part of the frond and consists of the following:

-

Midribs, locally called “Al-ʿaṣāy”, are the central veins of the fronds, entirely lacking in leaves and spines.

-

Leaves, locally called “Zaaf”, extend on both sides of the midribs.

-

Spines, locally called “Al-shwak”, are mutant leaves of varied lengths that grow between the leaf’s tip and its base.

b.2

The leaf base represents the lower part of the frond, and is composed of the following:

-

Petiole, locally called “Al-Karnaf”, is the base of the frond.

-

The leaf sheath, locally called “Al-Fadam”, is a fiber network that surrounds the petiole.

The treatment of date palm trees, as documented in [57], is as follows:

The average height of a date palm trunk is approximately 12 to 15 m, with diameters reaching up to 0.60 m. The height and diameter depend on the species and the spacing between the trees, typically 4 to 6 m. Palm trees with trunks exceeding 15 m in height are replaced by cutting them down due to safety concerns, which explains the selection of undamaged and date palm trees with dry dates (termite-resistant).

A carpenter’s smooth chisel, locally called “Imri”, crafted from the Acacia nilotica subsp. adansonii trunk, locally called “Agga”, is used to cut the trunk transversely into sections that do not exceed 2.5 m in length. Next, each of these pieces is divided lengthwise into two halves, and in the worst circumstances, each half is further divided into four pieces, which are also dried for a few days outside. They are pruned before being used to create a smooth surface on which to work; the pruning residues (segments of date palm trunks) are locally called “Alqashab”, and the final product is locally called “Khashaba”.

In addition to using date palms, various termite-resistant trees and plants have been used in earthen buildings, particularly near the Grand Erg Occidental, such as Tinerkouk, Charouine, Talmine, and Taghzouti. These include the following (Figure 17): Tamarix aphylla (locally called “Taberket”), Tamarix gallica (locally called “Azwa”), Acacia raddiana, Retama raetam, Calligonum azel, and Aristida Pungens Desf (locally called “El-Drin”). Currently, exploiting these trees and plants is illegal [58,59], except for scientific research conducted with specific methods and techniques [60]. This is aimed at preserving the ecosystem in desert areas. These species play a crucial role in stabilizing dunes, so protecting the desert ecosystem is crucial; excessive exploitation threatens their natural wealth, especially if they are removed from their roots.

4.2.4. Lime

Locally called “Al-Jeer”, according to Ouamar Abdelhai [28], lime was not widely spread because its use was limited to painting tombs and mausoleums, which was ritually performed once a year. The process was traditionally performed by burning lime. Lime is often confused with tuff, which is presently used on roads, and is also locally called “Tibshamat”.

4.2.5. Vegetal Fibers

One of the most commonly used types of vegetal fibers is wheat straw, locally called “Bromi or Aramo”. It is placed under the thick layer of mud to fill potential gaps, prevent mud and rainwater leakage, and minimize dust from falling through the roof when walking on it.

4.2.6. Animal Hides

Untreated animal hides are used in roofing as a waterproof barrier against rainwater leaks, and dromedary camel hides make ropes for binding palm tree wood doors.

4.3. Methods and Techniques of Building Components in the Region’s Structures

There is a diversity of building materials and building typologies with minimal natural interventions; these skills and methods include: the following.

4.3.1. Foundations

(a)

The rocky plateau as a foundation: This type of foundation usually exists in military architecture. Plateaus are either built with earthworks or without them; so, foundations are built with them or without them (Figure 18).

(b)

Stone foundations: these are the most common type currently in the region. It appears evident that the presence of foundations in the region’s buildings is not linked to the type of soil (Figure 19); the soil may be rocky with or without foundations, and it is built as follows:

• Excavating and preparing a trench in the ground, with depths ranging from 0.5 to 1 m.
• Laying stones of various sizes and shapes in the trench, with the average thickness of the foundation from the bottom reaching up to 0.8 m, allowing for it to protrude above the ground surface to build walls.

4.3.2. Adobe Bricks

Adobe bricks were molded in wooden or iron molds, usually without any additive or stabilizer except sand or tuff (such as in Talmine), and their dimensions can reach up to 0.17 × 0.17 × 0.4 m (as seen in Ksar Timimoun). The currently used dimensions are 0.15 × 0.15 × 0.35 m and 0.15 × 0.15 × 0.3 m. In the region, whatever the mold types and brick sizes, their production can be summarized in four (4) steps, as shown in Figure 20:

• Extract clayey soils by digging.
• The preparation of the clayey paste involves several steps:

  2.1.

  Dry mixing with available sand or tuff.

  2.2.

  Wet mixing with the addition of water.

  2.3.

  Macerating the clayey paste for an extended period with periodic water additions.

• Shaping and molding.
• Sun drying.

Producing adobe bricks is preferable during the spring or fall seasons, when temperatures are moderate and the sunlight is less intense. Conversely, production is prohibited in winter due to the harm it poses to builders, especially during the wet mixing process, which is performed barefoot. The rule states the following: “There should be neither harming (ḍarar) nor reciprocating harm (ḍirār)” [62].

4.3.3. Walls

After finishing the foundation preparation, load-bearing walls begin to be constructed. Based on their building materials, walls are classified into two types:

(a)

Stone walls: These are the most common type in the region, and according to oral tradition, buildings with stone walls are considered the oldest. This type of wall comes in two forms:

• Rubble stone walls: Undressed stones are used in this type of wall, with various sizes and types (Figure 21). The average thickness of the fortified walls at the base reaches about 0.8 m.
• The wheat spike wall’s method: This technique is rarely found in the region. Stones are arranged in a pattern resembling wheat grains in the spike, with a slope angle of up to 45° (Figure 22).

(b)

Mud walls: Based on the shape of the brick, they are classified into two types:

• Mud walls in the shape of a triangular prism: According to oral tradition, this technique is considered one of the oldest forms of mud walls in the region; they are manually formed, with dimensions of 0.1 × 0.1 × 0.1 m (Figure 23).
• Adobe brick walls: These are built from adobe bricks and mud mortar, and their thickness may reach 0.6 m. Whatever the brick sizes, walls in the region are in four shapes (Figure 24):

  -

  Stretcher bond: this bond is used on the first floor to separate between neighboring houses’ walls and does not exceed a height of 1.5 m. The thickness and height represent a social indicator of the level of safety and camaraderie among neighbors [28].

  -

  Header bond: this bond is used to separate different spaces within the house on floors and in the walls of the upper floor overlooking the alleys.

  -

  English bond with one brick wall: this bond is used for the same purpose as the header bond;

  -

  English bond with one and a half brick walls: this bond is used especially on the exterior walls facing the streets on the ground floor.

(c)

Mixed walls: This involves mixing different irregularly shaped and sized building materials within the same wall (Figure 25), and requires the filling of gaps with suitable stones or bricks and bonding them with mortar. Then, walls are covered to conceal any inconsistencies in the parts and enhance their appearance, although sometimes they may remain uncovered.

4.3.4. Buttress

Locally called “Al-Arsa”, the buttress is what the wall leans on to prevent it from falling (Figure 26). It is built in the same way as walls. Its purpose is primarily structural: to strengthen the walls and reduce the intensity of winds, on the higher walls. Over time, it can be added to the building with certain constructive customs, such as respecting the right of way. Also, it can be used at entrances for more aesthetic purposes than structural ones.

4.3.5. Columns and Arches

Columns and arches are made of adobe bricks or rubble stones, generally lacking the capital and base elements (Figure 27). After building arches on them, they serve as roof supports. Columns and arches in the Gourara are found mainly in religious architecture.

Arches are built by filling the space between the ends of the wall or columns with rubble stones or bricks. The desired shape of the arch is formed either by rubble stones or bricks or by using green date palm midribs [28] that bend and tighten between the ends of the wall or columns. After the arch hardens, the stones, bricks, and green date palm midribs are removed to obtain the desired arch (Figure 28).

It has been noted that during the French colonization of the region, arches witnessed an unusual increase in their size due to the introduction of large iron molds [28]. Additionally, arches were no longer limited to religious architecture.

4.3.6. Door Installation

Doors are crafted by assembling date palm trunks after treatment, connecting them with wooden beams, fixing them with iron spikes, or tying them with leather ropes (Figure 29). The doors are fixed by placing two outstanding wooden pieces (dowels) on the upper lintel and the lower threshold, allowing the door to rotate. The doors in Gourara buildings were limited to main entrances and granaries’ storage rooms, and they were completely absent in living rooms.

4.3.7. Staircase Construction Techniques

Stairs in the region are constructed in two ways:

(a)

A built staircase: this is the most common method in the region due to its simplicity. The staircase is built between two walls, or between one side of the building and half of another wall, without using a balustrade (Figure 30). The gaps under the staircase are filled with soil and stones and can never be exploited, while the steps are gradually built up to reach the roofs.

(b)

A built staircase on an inclined roof of date palm trunks: After determining the inclination angle, the staircase is constructed on an inclined roof of date palm trunk beams supported on the upper side by the building’s wall and fixed at its lower end to a wall with built-in steps (Figure 31). The staircase steps are constructed using stones or adobe bricks, with a height ranging from 0.2 to 0.4 m. Utilizing the space under the staircase is one of the benefits of this technique.

4.3.8. Roofs

(a)

Date palm trunk roof: This type of roof uses date palm trunks as beams, with a length not exceeding 2.5 m, leaving a distance of 0.15 to 0.25 m between them. The beams are fixed with stones and mud mortar to prevent them from rotating on their axes. Then, various possible joists, which support wheat straw, leaf, or animal hides, are placed on top of the beams. They are covered with a thick layer of mud mortar, which does not exceed 0.50 m at most. This type varies in the following ways (Figure 32):

• After placing the beams, date palm midribs are positioned adjacently on top as joists without leaving space between them.
• After the beams are placed, date palm midribs are placed on top of them in the opposite direction, spaced by 0.15 m at most. Then, on top, the date palm blades are positioned adjacently in the same direction as the beams. These are the prevailing roofing methods in the Gourara region.
• After placing the beams and leaving a space between them of 0.4 m at most, segments of date palm trunks are positioned adjacently to each other on top of them as joists.
• After placing the beams and leaving a distance of 0.25 m between them at most, petioles are positioned adjacently to each other as joists. This method is considered foreign to the region, as these roofs were found in buildings constructed during the French occupation.
• The beams are placed adjacently to each other without leaving any space between them. This roofing method is commonly employed in religious architecture, mainly in Zawiyas.
• After the beams are placed, flat stones are placed on top as joists, and the distance between beams depends on the length of the stones used.
• After placing the beams and leaving a distance of 0.25 m between them at most, tree branches are put on top as joists.

(b)

Tree trunk roof: This type of roof is rarely used due to the mechanical properties of local tree trunk wood. Tree trunks are placed as beams (Figure 33), and flat stones are placed on top of them as joists, covered with mortar. Tree trunks may be used alongside date palm trunks on the same roof.

(c)

Stone roof: For this type of roof, flat stones are used as beams and joists simultaneously (Figure 34), covered with thick mortar. This technique is found in areas abundant in flat stones, such as the Ighamawen of Aghlad-Ouled Said.

Giving the roof a slope and providing it with gutters made of date palm trunk after removing its core is considered the best way to protect the roof and dispose of rainwater.

(d)

Domed roof: The origin of domed roofs in the region can be traced back to the Negroland builders [63]. This is evident when comparing the shape of domes in the region with those in Negroland, such as the Djingarey Berre and Sankore mosques in Tombouctou and the Larabanga mosque in Ghana. This indicates the extension of African architecture to the region on the caravan trade route. Currently, building domes in the region is considered a disappearing skill.

In the Gourara region, domes are found in funerary architecture, specifically in mausoleums, and above some foggara built during the French colonization of the region. They are pyramidal or conical and may be erected on a square, rectangular, or circular base (Figure 35). The building materials are typically adobe bricks, rubble stones, or both.

In the Gourara region, five conical domes with circular bases were found, all located in the capital of the region (Timimoun): two in the Amghayr foggara, two in the Tyouchiet foggara, and one in the tomb of Lalla Zahia.

4.3.9. Mud Plaster

The primary role of mud plaster is to protect buildings against various damaging factors, and its application method is to fill the gaps and joints in the walls to achieve a relatively smooth surface. A final layer of mud plaster is applied. In contrast, the surface of the plastering is treated in various ways, depending on its location (Figure 36). It can be smoothed on the interior of the building by using hand float or sculpture mural techniques or roughened on the exterior walls by using hand fingers, the date palm spadix stems technique, throwing earthen hand-balls, or trowel earthen balls. However, in other cases, mausoleums were, until now, coated annually with the milk of lime as a religious ritual. Finally, the gaps may be filled without cladding or left untreated in stone or brick walls.

4.3.10. Floors

Floors are made of thick mud mortar covered with smooth, clean sand (Figure 37), which is changed periodically, at least every six months.

5. Discussion

Throughout different historical eras, earthen architecture in the Gourara region [36] is distinguished by the diversity of its construction techniques and materials, which are dominated by clayey soil. It is thus a result of residents’ interaction with their physical environment in the oasis system [43]. According to E. Fodde [27], documenting traditional earthen building techniques can be a significant step toward conserving earthen architecture and contributing to defining the nations’ heritage [53]. Subsequently, O. Sacko [7] concludes in his study that involving local communities contributes to preserving architectural heritage in the Sahel-Saharan region.

In addition, this study documents earthen construction techniques and materials in the region’s buildings, which could help preserve the EAH of the Gourara region. On the other hand, the study can also be a reference for the local authorities to promote EAH in light of the encouraged Algerian legislation, especially Executive Decree 23–401, Article 8, which concerns the methods of preparing prescription books’ architectural features: “The prescription books are prepared in two stages: diagnosis, such as identifying heritage characteristics, and identifying extraneous and inconsistent elements [52]“. This last step is largely consistent with what many recent studies and leading countries in heritage management report [18].

6. Conclusions

According to Algerian legislation, earthen architecture in the Gourara region is considered a part of the local heritage and requires a new vision for its protection. From this study, which concerns the earthen materials and techniques in the region’s buildings, it can be concluded that despite the decline in the oasis system for nearly 53 years, an essential number of earthen buildings still exist. This is the case even without legal preservation methods, although customary local preservation methods have been used. Even with the French presence in the region, EAH was not directly affected, for example, by the expansion of the city of Timimoun, which was built adjacent to the current historical city with the same usual building materials and techniques, unless necessary; thus, the buildings produced during that period became part of the local heritage. Therefore, the real concern, now that the region has been upgraded to a wilaya, lies in the management and dealings of local authorities with EAH. This is particularly true in light of the requirements mentioned above, and considering the extent to which sovereign decisions can accelerate the deterioration of EAH, especially if EAH is not taken seriously.

Through this study, it has become evident that the earthen construction techniques in the region are characterized by the general use of clayey soil in the various stages of construction, including foundations, mortar, brick-making, walls, roofs, and other techniques, without forgetting the use of other raw local building materials, such as stones, lime, and palm wood. By investigating these buildings, we learn about many skills that have disappeared or are on the path of disappearance. Similarly, many recent studies have dealt with earthen building materials and techniques to preserve EAH. Great reliance is placed on local authorities in the new wilaya of Timimoun to protect and promote this heritage, which will contribute to advancing local development, preserving the environment, saving energy, and confronting the dangers of sand encroachment, with the possibility of finding some practical solutions that may contribute to reviving the oasis system by adapting contemporary requirements. Finally, below are some suggested recommendations for preserving the EAH in the Gourara region, which could be more effective than the laws and their misinterpretations:

• The necessity for local authorities to construct earthen architecture prototypes or restore earthen buildings is evidence of the level of awareness about preserving EAH. For example, in June 2024, the local authorities took the initiative to restore the Amghayr foggara.
• It is important to coordinate between the local authorities and CAPTERRE to organize volunteer workshops, previously carried out in 2016, 2018, 2019, 2021, and 2023, to urge residents to preserve their EAH.
• Heritage preservation should be promoted through various local media platforms.
• The notion of heritage preservation should be instilled in the younger generations.
• Emerging projects to protect and promote heritage should be facilitated through the Algerian Ministry of Knowledge Economy, Startups, and Micro Enterprises policies.