Artificial lightweight and porous materials (i.e., architectural greening soils and materials) are often used in the rooftops and wall greening of buildings. It is important for the designers of the system to understand the physical properties of architectural greening soils and materials to save the amount of water and fertilizer used, which directly affects maintenance costs. The aims of this study were to assess the pore size distribution of architectural greening soils and materials for wall greening based on their physical properties. According to water retention measurements, rapid drainage will occur at particular matric potentials for certain architectural greening soils and materials. The pore size distributions of architectural greening soils and materials estimated from water retention curves suggested that the architectural greening soils and materials used in this study can be classified into two groups: (i) materials that include only relatively large pores with diameters from 0.001 to 0.01 cm, (ii) materials also include relatively small pores with diameters from 0.0002 to 0.001 cm. The classification of architectural greening soils and materials by pore size distribution could be affected by their manufacturing processes. The values of saturated hydraulic conductivity of the materials ranged from 10^0 to 10^{-2} cm s^{-1}. Furthermore, hydraulic conductivity tended to increase with total porosity of the architectural greening soils and materials except that whose pores were made by forming.