in 1903, in response to an outbreak of bubonic plague, the hong kong government issued a set of new regulations for "tong lau" so as to improve the living condition of those in these buildings. new "tong lau" buildings needed to have a light well, have larger windows, and the buildings were limited to four floors so their residents can receive sufficient light. the frontage were set at 15 feet, and at the back there needed to have a 6-foot lane to remove back-to-back constructions. roof tiles were also replaced by flat concrete roofs.