Helmsley Place is a mixed-use commercial and residential scheme located in the London borough of Hackney, consisting of a core five-storey layout with additional basement and mezzanine levels to provide adequate, comfortable space to work and live. Above the offices in the lower two storeys are eight build-to-rent residential flats, each equipped with its own private terrace. To execute a design process that carefully met the client’s needs, we took a collaborative approach alongside the Design & Build team, where open dialogue and frequent meetings were necessary to respond to an ambitious proposal while address design, technical, regulatory compliance and construction cost efficiencies. The scheme is aiming for a BREEAM Excellent rating, certifying the sustainability of the build. Prior to undertaking the design work, we were appointed to review the scheme. We thoroughly assessed the plan, highlighting potential issues, flaws, and risks, as well as evaluating the standards of compliance for the project. Thus, the client selected AB Architects to design the mixed-use new build due to our expertise in consulting, design, technical work, and construction on residential, commercial, and mixed-use projects. This ambitious plan presented some design and construction challenges primarily due to the recessing massing on the upper floors, the required retention of the rear elevation wall, the integration of green roofs, the mixed-material structure, and the commercial mezzanines, subterranean levels, and basement floor. Both the fully-underground basement level, designed to house maintenance services and cycle storage, and the lower office mezzanine required a thorough waterproofing design to ensure the longevity of the build. The structure is designed with reinforced concrete on the lower floors and steel frames on the residential floors. Due to the fact that the structure is intended as a multi-use development, the design involved thorough plans for fire and building regulation compliance which were met through careful planning. Overall, the structure delivers eight residential units, two office floors, two mezzanine floors, and a basement level across 3500 sqm of internal space. With the best sustainability practices in mind, the roofing plans entailed all blue/green sedum roof systems that offer both aesthetic and environmental benefits which are preferred for storm-water performance and compatible with the PV panels of the main roof.