Citation: Senarathne, H.N.Y.; Asmone, A.S.; Chew, M.Y.L. Developing a Waterproofing Decision-Making Model for High-Rise Building Projects in the Tropics. Buildings 2023, 13, 2328. https://doi.org/10.3390/ buildings13092328 Academic Editors: Jurgita Antucheviciene and S.A. Edalatpanah Received: 14 August 2023 Revised: 4 September 2023 Accepted: 8 September 2023 Published: 13 September 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). buildings Article Developing a Waterproofing Decision-Making Model for High-Rise Building Projects in the Tropics Helapura Nuwanshi Yasodara Senarathne 1 , Ashan Senel Asmone 1, * and Michael Yit Lin Chew 2 1 Department of Building Economics, Faculty of Architecture, University of Moratuwa, Moratuwa 10400, Sri Lanka 2 Department of Built Environment, College of Design and Engineering, National University of Singapore, Singapore 119077, Singapore * Correspondence: ashan.a@u.nus.edu; Tel.: +94-112-650-738 Abstract: The most severe problem in high-rise structures is a failure to achieve watertightness. Since the presence of water in a structure can have a detrimental impact, adequate consideration must be taken when selecting a suitable waterproofing system based on several factors. As a result, this research aims to examine the factors that affect the selection of the best waterproofing solution in high- rise building projects in the tropics. Preliminary observations were conducted to investigate typically occurring issues with high-rise buildings which contain commercial, office, and residential facilities. Data were collected through questionnaire surveys and semi-structured interviews with professionals in the waterproofing industry. This study provides a comprehensive understanding of the issues concerning waterproofing and suggests an effective solution for the same. The assessment of the best waterproofing selection criterion was analyzed by incorporating the Best Worst Method (BWM). Based on the global ranking reached, the decision-making framework was developed, and three main specifications, technical, construction, and product, were suggested to select an ideal waterproofing solution. This study provides insightful guidance for professionals in the waterproofing industry and their clientele towards an optimal solution, facilitating informed decision-making processes. Keywords: building defects; Best Worst Method (BWM); Multicriteria Decision-Making (MCDM); decision-making framework; waterproofing 1. Introduction Since the tropical environment has a distinct climate [1], including elevated temper- ature patterns and specific precipitation patterns, waterproofing is crucial for high-rise buildings in such a setting [2]. A monsoonal climate, which denotes high intermittent rainfall events, changing water tables, cyclical saturation level, and unsaturation with related chemical shifts and floods, is present in many tropical regions. This suggests that buildings in tropical areas have a propensity to deteriorate fast, particularly when it comes to external building materials that are exposed to factors including rain, wind, sunlight, UV radiation, and air pollution [3]. Major defects and persistent problems in high-rise buildings are caused by water [4,5]. Accessible water is carried into a building structure by a variety of mechanisms, including hydrostatic pressure, capillary forces, tension on the surface, air currents, and natural gravitation [5]. The main cause of moisture problems in buildings is leaks in structural elements such as the roof, wall, and ceiling [6]. There are several ways that water may enter a building, including through cracks, expansion joints, openings in the walls and roof, and solids that are porous in nature. Any surface area that comes into the path of water possesses the potential to let water in or potentially leads to water coming into a structure and must thus be waterproofed [4]. According to the definition of waterproofing, it is “a method to protect the structure from moisture on the surface or filtering water from groundwater, precipitation, or other Buildings 2023, 13, 2328. https://doi.org/10.3390/buildings13092328 https://www.mdpi.com/journal/buildings