Due to our experience in developing residential, commercial, and mixed-use projects, following planning permission was granted, AB Architects were selected to create the design development and technical design, and facilitate the construction stages to completion. The project consists of five residential units for private rent, two of which are duplexes. The building is articulated within 550 square meters of internal area over four levels to include a fully-habitable lower ground floor. The approved site for this five-unit new build was a constrained, sloping location with a set budget. As such, the overall project presented design and construction challenges with regards to the irregular nature of the land plot and the construction of an entirely subterranean habitable basement level. However, the design challenges presented by the constrained and ambitious planning approved scheme were resolved without compromising on spatial quality, construction budget, internal layouts or usable, habitable space. A collaborative approach with the Design & Build Team was necessary to respond to an ambitious design program while addressing design, technical, regulatory compliance, and construction cost efficiencies. Regular meetings and a continuous open dialogue throughout the design improvement process helped promptly answer questions, keep other disciplines consultants informed, and propose and integrate alternative design and construction solutions. We listened to our client carefully to understand objectives and priorities without imposing a one-size-fits-all approach. The client had a fixed budget and a set of guidelines for the finishes and aesthetics of the project. Due to the nature of the site and the original planning permissions, satisfying building regulation standards proved difficult. We reviewed and improved all flats layouts, making them more inviting and usable to prospective tenants while also ensuring building regulation compliance, improving the process's efficiency, and incorporating contributions from contractors and specialists. The building includes a fully-habitable lower ground floor, naturally lit by generous lightwells, and requiring a thorough waterproofing design for use as intended. The site's irregular triangle shape and multidirectional slope posed a challenge in the overall construction executions. Additionally, the depth of the light well had to be reduced to accommodate sheet piling and to avoid impacting the use of the pavement. This resolved a significant construction complexity for the general contractor and specialist subcontractors, cutting out costs and additional local authority approvals. We increased the amount of sunlight coming from the light wells, making the best use of the space. The approved scheme presented some challenges regarding roof constructability. Although the planning permitted scheme included a traditional roof design, the geometry proved problematic to build, and required a reassessment of the top floor flatlayout. Step-free access wasn't possible due to the constrained site, forcing us to explore several ramp options at the building's front and back. After reviews and discussions, building control accepted stepped access due to the impracticality of the ramps, saving further costs. During construction, the team discovered that the services crossover was higher than indicated on plans and surveys. We redesigned the parking area levels and drainage to suit the newly-discovered situation to avoid extra costs and delays. To elevate the scheme and create the highest possible level of spatial quality, we focused on reviewing layouts, such as changing the bathroom location, improving services distribution to minimise raisers space and services transfers, and implementing full-width shower trays and full-width mirrors where possible. This project offered us the opportunity to work closely with the construction team, subcontractors, and suppliers throughout, from design development to pre-construction and construction stages. We optimised design solutions to deliver cost and programme savings without compromising on quality or performance. The project has been completed on time, and on budget and was fully let upon completion.