Heritage is considered a part of national identity that connects us with the past, showing the value of history, and stands as a tradition for future generations [1]. However, heritage assets are directly or indirectly exposed to dynamics such as environmental changes, structural loads, and so onetc., causing continuous deterioration during their operational stage [2]. Restoration techniques are applied to preserve heritage structures, which helps extend their life. However, during restoration, the biggest concern is the lack of documentation and unavailability of the as-built information, which creates many problems such as inefficient project management, increased cost, and increased duration of the restoration and management process. To address these problems, an advanced documentation method must be adopted for heritage buildings, to have a geometrical model with all the information in a single database that supports the restoration process effectively and the operation and maintenance (O&M) phase. Identification and digital documentation of the actual condition and the properties of the heritage building components will benefit the stakeholders in making effective decisions throughout the lifecycle. The management of the three-dimensional (3D) model containing all the semantic information about the heritage assets—to provide a collaborative information management platform—will reduce the difficulties involved during the operation, conservation, and reconstruction stages [3].

Building information modeling (BIM) is one such process that is continuously developing in the architecture, engineering, and construction (AEC) industry, which integrates the 3D model with all the semantic information throughout the project lifecycle [4]. BIM digitizes, integrates, and manages all the related information in a single database based on a 3D model that can be used for the whole lifecycle of the facility. The BIM model information increases with the dimensions that have been framed into seven levels and is still extending ^[5][6][5,6]. It can integrate design and construction drawings, construction methods, construction time and cost schedules, and process documents with the 3D models to provide information in 4D and 5D models in a single format that play a key role in the integrated project delivery (IPD) method [7]. Furthermore, BIM capabilities of integration with facility management (FM) information provide valuable insights for facility managers to support FM tasks [8].

Despite the various dimensions and applications of BIM, interoperability is the researchers’ main concern in BIM-based workflows. The industry foundation class (IFC) can be used to address the interoperability issue [9]. IFC is an open and neutral standard that provides interoperability and integrates information from different sources in BIM in a well-structured way. It can be implemented in the project to exchange 3D object data, including information, regardless of the used software by the project team.

Unlike the new-build construction projects, BIM application in the heritage sector is a relatively new academic research field. The challenge with historic buildings is that the elements are not similar and thus difficult to standardize. Most of the elements are unique, implying that many have irregular geometries and shapes along their length. Heritage buildings are still managed using traditional method that lacks providing the heritage data in a single digital database. It is managed by multiple format systems involving several stakeholders working with their system. The multiple format system is characterized by various formats such as PDF documents, words report, excel spreadsheets, and so onetc., that are hardly linked and lack integration. It also is supported by 2D representation, thus lacking 3D visualization, making it hard for managers to make critical decisions. The retrieval and update of information from such a system is challenging. For example, obtaining information for a specific heritage component from such a system is difficult and time-consuming during the maintenance tasks. Moreover, data exchange among the stakeholders is difficult because the various formats create a lack of collaboration and a communication gap. Adopting such a traditional method creates many problems during the restoration process and FM.

The BIM concept in the heritage sector was developed in 2009, called heritage building information modeling (HBIM) [10]. The HBIM system is the management system for heritage structures to store the integrated 3D model and its historical semantic information. This system has significance in integrating historical information such as documents, structural information, monitoring information, and the current state of the building in the 3D environment [11]. Recently, HBIM has been applied to heritage buildings, such as scan to BIM and parametric reconstruction ^[12][13][12,13]. However, the application of HBIM to integrate the semantic information specifically related to the heritage management and lifecycle data at a different period with complex geometries, and its use for the reconstruction planning and FM activities, are very rarely explored. Insufficient attention has been paid to the required information for heritage management, such as those needed by owners, compared to the 3D modeling of the heritage buildings. The application of HBIM to integrate semantic information and use it for the management of heritage buildings is urgently needed to help the owners and the organizations make valuable decisions over the lifecycle. Furthermore, there is a knowledge gap regarding FM integration with BIM for heritage buildings in Pakistan. The focus of our study is to fill that knowledge gap in terms of such studies in Pakistan.  Our aim is to introduce FM integration with BIM for heritage buildings in Pakistan, which has not been implemented yet. Hence, our study will work as starting basis for further research and innovation in this field in Pakistan.

An HBIM framework that capture, document, and manage heritage building information from multiple sources in a single BIM database and utilize it to support the documentation, restoration planning, and FM processes. CThe paper contributiones to the IPD will be b by defining and involving all the participants needed to facilitate the heritage FM. A business process modeling notation (BPMN) provides a process map that identifies the integration and exchange of the information provided by each involved stakeholder. Furthermore, IFC is used to enhance the information exchange among the stakeholders. As-built BIM models are developed and enriched with the required FM information that acts as a central repository of the information for all the heritage assets. Stakeholders can access this information when needed. The developed novel framework is implemented on a heritage building site to demonstrate and verify the actual potential and benefits in the heritage sector. 

Heritage has been divided by United Nations Educational, Scientific, and Cultural Organization (UNESCO) into a natural, cultural, and underwater heritage. It is defined as “our legacy from the past, what we live with today, and what we pass on to future generations” [14]. Moreover, tangible and intangible cultural heritage are the two categories that divide cultural heritage (CH). Heritage shows a nation’s identity and past legacy for the future generations ^[1][15][1,15].

Heritage buildings need proper maintenance, which are the routine works essential to keep the status of the heritage buildings. For example, the repair and maintenance work of those heritage elements that are needed to enhance the elements’ life, such as walls, columns, and so onetc., even the entire heritage building. The maintenance activities increase the performance and life of the heritage buildings, also ensuring the functionality of each element, preserving the heritage, and making the heritage sustainable for the future. These maintenance activities include preventive maintenance and corrective maintenance. Preventive maintenance is performed at regular intervals regardless of the heritage asset condition; for example, scheduled tasks that are conducted to check the status of the heritage elements. On the other hand, corrective maintenance is performed after the failure has occurred; for example, when severe damage occurs to the heritage assets that need maintenance task for their restoration.

Restoration techniques are applied to make the heritage elements functional and bring them into their original state; it aims to restore the heritage value as close as possible after the damages. For example, the material can be replicated, or some part of the heritage element can be reconstructed to keep the high level of originality. During the restoration planning, the restoration process is planned, and the resources, time, and cost used for that process is defined to minimize the risk and make the process efficient [16]. Maintenance and restoration activities are performed in the heritage buildings; however, the stakeholders face problems during these activities, because of a lack of as-built information about the heritage buildings [17].

The benefits of adopting BIM in the AEC industry are widely known for the digital documentation by providing an integrated environment [18]. For example, it provides a parametric design tool for 3D modeling that can be visualized in a virtual environment, showing existing features. BIM tools not only facilitate 3D representation, but also combines and empowers the information management of various facilities ^[19][20][19,20]. Despite the BIM uses and benefits, its application in the heritage sector is still in the early stages because of the divergence of heritage projects. The heritage buildings exhibit complex geometries [21]; hence, it is difficult to standardize heritage buildings. Traditionally, a project information model (PIM) is developed from the data generated during a BIM workflow’s design and construction stages. However, heritage buildings are already constructed and involve architectural, archeological, and historical information that must be managed for the restoration, operation, and maintenance stages [22]. Therefore, an accurate 3D digital model is needed to reconstruct and document heritage buildings using advanced photogrammetry, laser scanning, and BIM [23].

The HBIM concept has been used recently for the effective modeling, documentation, conservation, and classification of historical architectural elements ^[10][24][10,24]. A heritage building model can be developed by obtaining graphical data using 3D laser scanning and photogrammetry [24]. In the laser scanning technique, the surface of the heritage buildings is captured by a set of digital data points that represent the geometry coordinates in 3D space [25]. The laser scanner uses a laser beam that focuses the target and the reflection of the beam provides the precise geometry of the heritage [26]. On the other hand, photogrammetry uses camera images to obtain the as-built heritage surface information. Images are taken with a camera with predefined ground control points (GCPs). The images are processed using the Structure for Motion (SfM) algorithm [27]. These methods provide point cloud data consisting of millions of points with geometric coordinates showing the precise geometric representation of the 3D objects [28]. Cleaning and filtering of the point cloud are needed before preserving the complex geometry of the heritage building [29]. Although the processed point cloud shows the historical geometries’ original complexities, it does not contain additional information such as attributes information, which are significant for the management activities. Therefore, converting the point clouds into parametric 3D geometrical models is necessary to incorporate additional information about geometry, material, and attributes ^[28][30][28,30].

HBIM provides a modeling environment where the point cloud can be converted into a 3D model. However, during management, the information is exchanged among the project participants, which is difficult. Therefore, the industry foundation class (IFC) can be used to enhance the information integration and exchange. IFC provides the project information in a hierarchical manner and geometrical and non-geometrical data can be integrated, managed, and shared among different participants. The parametric 3D modeling of the historical buildings allows storing information about the cultural, social, environmental, maintenance, and other artifacts ^[31][32][33][31,32,33]. In addition, intangible heritage characteristics can be integrated with the 3D model in a more consistent and structured way. All the data sources are combined into a single database that provides easy access and information extraction. The parametric historical BIM model containing semantic information can serve as a database. Information can be extended, edited, exported, and updated continuously during the conservation, repair, and maintenance (CRM) activities.

HBIM can assist widely in capturing the complex historical geometries using photogrammetry and laser scanning techniques and the development of 3D parametric models [34]. For example, the HBIM concept has been used to store the decay data of a timber heritage structure and used to compare the status of the heritage structure ^[34][35][34,35]. Furthermore, 3D models have been developed integrating heritage documents for documentation and conservation ^{[13][36][37][38]}[13,36,37,38]. However, these studies are either applicable to specific heritage types, such as timber structures ^[34][35][34,35], or integrating documents with the BIM model, limiting applications to support FM tasks and restoration planning. Moreover, the definition of the semantic information and the stakeholders needed to support such processes are rarely focused. Therefore, the existing capabilities of the HBIM can be extended by integrating the semantic information involving different stakeholders to support the documentation, restoration planning, and FM activities in the future.

Figure 1  summarizes existing studies about BIM, its application in the heritage sectors, FM and restoration planning, and their integration. Using open standards, BIM has been applied for 3D parametric modeling, project planning, and lifecycle management. The implementation of BIM is highly acknowledged to be beneficial for the design and maintenance of new buildings. Furthermore, its application in heritage building is widely adopted to scan the as-built heritage assets using photogrammetry techniques and the conversion of the heritage scan model into a parametric 3D digital model with attached documents. However, there is a research gap in BIM application for the restoration planning and FM of heritage buildings; also, the existing studies lack defined information needed for the maintenance and management of heritage buildings. The implementation of maintenance works, such as preventive maintenance and corrective maintenance, for heritage buildings is rarely discussed.  This research aims to bridge this gap by proposing a novel framework based on open standards (i.e., IFC) and implementing the proposed framework on a real case study of heritage buildings.