TABLE OF CONTENTS - The Professional Green Building Council

Theme B: Creating a livable, healthy and environmentally viable citiesProprietary lightweight aluminium alloy standing seam roofing system wasadopted in some projects as it could reduce structural loading and save buildingmaterials. The prefabricated system can also reduce material wastage on site.However, after the building occupation, there were reports of water penetrationafter heavy rainfall.Figure 1: Details of a typical roofing systemThe following causes of the problems were identified by the POE team:i. “Balloon-type” gratings to roof outlets at the gutters were installed as part ofthe standard system. Some of the inconspicuous gratings were found to beblocked by leaves and plastic bags blown onto the roof from surroundingareas.ii.Inadequate fall of the roof for maintenance requirements might have hinderedthe swift disposal of rainwater, especially after heavy rain during typhoonseasons in Hong Kong.iii. The standard upturn at the flashing cover was suspected to be too shallow andwater ingress was found at some of these locations.iv. Some damage caused by stepping on the roofing panels and the perimeterflashing by the contractors during construction and subsequently by themaintenance staff after the occupation were discovered. The provisions forthe protection of the metal roofing to cater for the routine inspection andmaintenance needed to be improved.The following solutions were adopted:i. Additional stainless steel mesh grating units of about 2m long were installedover the standard “balloon-type” gratings. Since the surface area of the529