The 1964 Venice Charter emphasized the importance of preserving cultural heritage in its historical context, underlining the need for continuous conservation in urban and rural areas. Conservation efforts preserve cultural assets for future generations and to use the knowledge accumulated over time. In rural areas, traditional architectural solutions reflect socio-cultural values, adapt to environmental factors such as climate and topography, and offer sustainable methods. The conservation of rural settlements and traditional building techniques has become a field of study for national and international researchers since the second half of the 20th century. Rural heritage, representing tangible and intangible cultural heritage, faces significant threats such as vandalism, abandonment, neglect, and loss of traditional handicrafts. This study describes the conservation problems of the architectural heritage, especially the mosques of the Principalities period, located in the rural areas of the Kastamonu Central district. 

When the traces of architectural heritage in rural Kastamonu are followed, it is seen that the traces of Turkish architecture date back to the 13th century. The first Turkish raids to the region started in 1081, and Kastamonu was annexed to Turkish lands in 1212 by Emir Hüsamettin Çoban Bey, one of the emirs of the Seljuk State. When the foundation records are examined, early architectural works belonging to the Çobanoğlu Principality can be seen in the rural areas. One of these structures is the Sheikh Ahmet Mosque, built in Gölköy Village. Another architectural heritage is the Akça-su Mosque, built in Şeyh Village. 

Çobanoğlu Principality ruled in the region for 97 years. With the Kösedağ War (1248), the Mongol influence in Anatolia and the political problems in the Anatolian Seljuk State enabled the establishment of the Candaroğlu Principality in the region in 1309. Candaroğulları also served as an end principality. The first known structure built by Candaroğulları in the countryside is the Halil Bey Mosque in Duruçay Village, built in 1363. In 1366, the Mahmut Bey Mosque was built in Kasaba Village, which is thought to have been used as the settlement of the Candaroğlu dynasty. With its construction technique and ornaments, this mosque is a cultural asset of high original value in the Kastamonu region.

The study carried out archival research and field studies for the four important mosques mentioned. Within the scope of archival research, the records of the Kastamonu Regional Directorate of Foundations, district mufti registry books, and Ottoman state archives were analyzed. Field studies included an inventory of the mosques, measurements, photographic records, and user interviews. 

The Şeyh Ahmet Mosque in Gölköy is a rectangular building with stone walls. Its original elements include a mihrab, a wooden ceiling, and a porticoed entrance. Over time, cement plaster and modern interventions have altered the original structure. Conservation issues include damp damage and inappropriate modern additions. The historical significance of the mosque derives from its continuous use as a social and religious center. However, inappropriate interventions have affected its structural integrity and historical authenticity.

The Akça-su Mosque in Sheikh Village dates back to the 13th century. It has a similar rectangular plan with stone walls and wooden elements. The original minaret was destroyed in an earthquake and was rebuilt using modern techniques and materials. The mosque’s importance stems from its use as a social center serving the surrounding villages during the Ottoman period. Modern interventions such as cement plaster and the replacement of original wooden elements with contemporary materials have created significant conservation challenges. 

The Halil Bey Mosque in Duruçay Village uses materials from early architectural works. The unique elements include an ornate wooden ceiling and reused Byzantine columns. Conservation strategies should prioritize the preservation of these unique historical features. The architectural significance of the mosque derives from its innovative use of different architectural traditions. However, environmental factors and inadequate maintenance have deteriorated these unique features and require urgent and careful conservation work.

The Mahmut Bey Mosque, located in Kasaba Village, is famous for its wooden structure and detailed painted decorations. In 2023, it was inscribed on the UNESCO World Heritage List under the title ‘Medieval Wooden Hypostyle Mosques of Anatolia’ together with the Great Mosque of Afyonkarahisar, the Arslanhane Mosque, the Sivrihisar Great Mosque and Eşrefoğlu Mosque. The detailed wooden architecture and ornamental elements represent the pinnacle of Beylik period craftsmanship. The rapid deterioration caused by visitor activities and environmental control requires a balanced conservation approach that includes managing touristic activities and environmental impacts.

This study analyzed four mosques associated with the Beylik period by observation. With the information obtained from archive records and oral interviews with the users, the interventions that the buildings have undergone were determined. The deterioration of the buildings was identified through observation, and the causes of the deterioration were discussed. The factors that cause deterioration in historical buildings are divided into environmental (natural) and human-induced. Causes that may arise from the initial construction of the building are excluded because they also affect the architectural values of the buildings. Environmental factors are categorized as disasters, sun exposure, rain and wind erosion, vegetation, fungal and insect growth, and ground conditions, while artificial factors are categorized as abandonment, vandalism, and faulty repair.

Surface losses due to rain and wind erosion were observed in the buildings. The spolia column capitals used in the last prayer hall of the Halil Bey Mosque in Duruçay Village have abrasion and fragment loss due to wind erosion. Since wood materials have an organic structure, they are exposed to insects and decay in case of insufficient drying during the construction phase or wear of the protective layer applied over time. The Mahmut Bey Mosque’s interior structure is made using the wooden interlocking technique. It was determined that the wooden materials of the mosque had blow holes and were exposed to dry rot due to fungus. The ground conditions on which the buildings are built caused some deterioration in the structure. For example, in the Duruçay Village Halil Bey Mosque, dampness was formed on the wall surfaces due to moisture from the ground. Another factor that causes deterioration in buildings is wrong interventions and faulty repairs. The continuity of use of the architectural heritage is important for the preservation of the building. Historical buildings face various risks, and as a result, deterioration and destruction occur. The unconscious application of relatively new materials and techniques, such as intervention with RC construction techniques, cement-based mortars, and replacing window openings with PVC material, damages the original values of mosques.

In addition to the geography of rural Kastamonu, the dominance of the continental climate in the interior, transportation difficulties, and the changing understanding of comfort are among the factors that cause the emptying of village settlements. Another factor is the changes in agriculture and animal husbandry policies after 1980. For this reason, the loss of the productive village identity led to the dehumanization of villages that already consisted of a few households. The decrease in the number of households in the villages also affects the number of congregations. According to the information from the oral interviews, the Akça-su mosque in Şeyh Village also faces this risk. The fact that the Imam hatib of the Akça-su Mosque is still on duty offers a solution to prevent the abandonment of the building.

Except for the Mahmut Bey Mosque, additional buildings were constructed for each mosque over time. This has resulted in new openings in the original body wall or existing openings' closures. Adapting historical buildings to today’s contemporary conditions and expanding them with additional structures is possible. However, in the mosques examined, some decisions were made that may harm the original condition of the building, and this situation affected the architectural and documentary values of the mosques. The intervention in the last prayer hall of the Halil Bey Mosque exemplifies this situation. For reasons such as ease of use and wind blocking, the PVC material with a wooden appearance was covered between the fluted columns with Corinthian capitals, and the perceptibility of the last prayer hall was reduced.

Except for the Mahmut Bey Mosque, the other buildings were plastered with cement-based finishing. This method of intervention, which was carried out to prevent mortar discharge between the stones due to environmental influences, damages the natural structure of the stone and reduces its strength. Within the building, it is observed that the wooden materials are painted to protect them against insects and decay. This causes the loss of the decorations on the pediments of the cloisters and ceiling cores. Other external factors to which mosque buildings are exposed are deterioration due to material wear during historical processes, atmospheric events, and natural disasters. When these risk factors occur, it is necessary to develop the appropriate intervention methods within the framework of expert opinion. However, the benefactor who built the Akça-su Mosque, whose body wall collapsed due to an earthquake in the first half of the 20th century, had the minaret built similar to a minaret from the Hejaz region. In this way, even a minaret added later affects the authenticity of the mosque.

Intervention and expert opinion in the conservation approach are important for the protection of buildings with original architectural value under registration. The buildings should be documented and evaluated in the context of their architectural history. However, this process alone does not offer a solution to a holistic conservation approach. Users need to be made aware of the protection of cultural assets and the values of the architectural heritage.

The four mosques analyzed were used as divan/Friday mosques serving several villages and forming a common social and cultural space during the Ottoman period.

These mosques have architectural, historical, documentary, spiritual, religious and esthetic value. All these values need to be transferred to the future. When conservation problems are evaluated, the main problems that cultural assets are exposed to can be listed as follows: Not having a holistic conservation plan, being exposed to environmental and human-induced deterioration, and unconscious intervention methods. In a holistic conservation approach, raising the conservation awareness of the local administration, the employees responsible for the mosque, and the village community is an important factor. Imams in charge of the mosque and villagers should be aware of their cultural heritage.

To protect the rural architectural heritage, stakeholders such as state institutions, local administrations, non-governmental organizations, experts in the field, and professional chambers, especially local people, should come together during the project and create a participatory conservation approach. In areas where intangible architectural heritage needs to be protected, the ability of local governments and state institutions to reach out to communities, groups, and individuals and their experience in conducting joint activities with non-governmental organizations is important for cultural heritage conservation. Therefore, stakeholders responsible for conserving these mosques should develop a holistic approach to conserving the tangible and intangible cultural heritage with professional associations, civil society organizations, users, and local communities. To this end, official institutions in the hierarchy, starting from the level of ministries to village representatives, should play an active role in inventory, documentation, and archive work, as well as in the use of tools such as education, awareness raising, press, and social media.

Mosques can be intervened with modern equipment against physical environmental conditions. Structural (reinforcement, ventilation, heating, lighting, etc.) evaluations should be made for these divan mosques with high architectural and historical value. Comprehensive analyses should be conducted for such interventions. For example, in interviews with the congregation of the Mahmut Bey Mosque in Kasaba Village, it was stated that the Friday and Eid prayers are performed collectively with the people living in the villages connected to the divan in the spring and summer months within the scope of the divan tradition. However, it was stated that the heating problem could not be solved in the winter months because the mosque had not intervened. It is important to prepare a comprehensive guide for the protection planning of the mosque where there is a fire risk.