Built early last century and situated in the heart of Surry Hills, Sydney, No 1 Lacey is an iconic former industrial building converted to a modern residential development. The existing post and beam system was designed to accommodate structural loads throughout the building’s industrial life and was constructed using local ‘ironbark’ mass timber column and beam members for the main structure with Douglass Fir deep floor joints. The identified heritage value of No 1 Lacey included the mass timber structure which was retained and expressed as exposed original timber through the application of a holistic fire engineering risk approach. Scientific Fire Services team of skilled engineers have extensive project experience in analysing existing structural timber in fire conditions. Occupant egress solutions were developed for the No 1 Lacey residential conversion and assessed on a performance basis to accommodate the egress design for residential use. Extensive structural analyses and human movement simulations were used to demonstrate that effective fire safety performance was achieved for occupants and fire fighters. Construction was completed in 2017 and is now part of the emerging Surry Hills heritage precinct.