111 Dixon Apartments
111 Dixon bathrrom pod being lifted on site
This ground-breaking urban apartment building saves time and cost by incorporating 228 imported, ready-to-go bathroom pods. Benefits include reduced packaging waste while eliminating the need to coordinate utility sub-contractors at site. PrefabNZ case studies "How to prefab" includes 111 Dixon apartments, download the case study here
This 20-level residential project required a cost-efficient and top-quality outcome with fast construction. The design incorporates 228 apartments, 228 bathrooms, and six commercial units. The key issues to manage were around programme, cost, quality, and safety.
111 Dixon render
The downtown site posed the expected challenges that correspond with an inner city development such as heavy traffic management issues and restricted access for loading. Another consideration was the labour required for the construction of the 228 bathrooms. The head contractor, Arrow International, considered the number of plumbing companies in Wellington who could undertake a project of this scale. During the time of consideration, the availability of subcontractors for a project of this size was limited. This factor could have led to potential budget issues for the overall project. In response to project challenges, Arrow International adopted Design for Manufacture and Assembly (DfMA) principles for the design. This meant the design was integrated with prefabricated bathrooms in order to increase safety, quality and cost advantages during construction. This early decision cut approximately six months off the scheduled programme.
Arrow International researched the local and offshore markets for potential bathroom pod manufacturers. A range of prices were available with almost $10,000 per unit difference between the highest and lowest costings. Arrow International visited two factories (one in New Zealand and one in China), to view their manufacturing processes, capacity, materials used, construction techniques, quality assurance, and production programme. The offshore product was selected for its high quality and cost-effective value. Their Quality Assurance (QA) system and manufacturing capacity proved their delivery capability could meet the project’s programme. The pods’ walls and ceilings are made from a composite panel that is lined with steel on the exterior and interior, while the floor incorporates a stainless steel drainage tray. The interior walls and floor are tiled to full height. The shower empties into a slot-drain, and the fittings incorporated consist of a glass shower screen, toilet, vanity with handbasin, and mirror. Bathroom units in this project have enabled health and safety benefits, reduced the number of staff and has improved coordination on-site. These benefits justified Arrow International’s decision to proceed with importing the units.
Bathroom pod interior
The bathroom pods are shipped to Wellington from the German owned and run factory in China. The units are then transported to site on a delivery truck, lifted by tower crane and lowered into the building through the lift shaft as the floor levels are completed.
The singular units are then moved into their final position by trolley. Each pod requires a plumber to connect them to the building’s water and drainage infrastructure - this takes an hour. The exterior of the pod is lined with plasterboard and integrated into the apartment’s internal fitout.
The overall building construction continues around the pod installation. Not only does this contribute to safety, due to the limited tradesmen needed at site, but also has a positive benefit for Health Safety and Environment (HS&E), as waste in the form of packaging from bathroom components is virtually eliminated from site. Due to using offshore-sourced pods, Arrow International faced risks associated with the QA of the product, obtaining building consent and Code Compliance, delivery to New Zealand on time, as well as the possibility of hidden costs. These risks were successfully mitigated by undertaking due-diligence including three factory visits, a detailed shop drawing and checking process, construction of example pods for inspection prior to manufacturing approval, and pre-building consent application meetings with the local Building Consent Authority (BCA). Arrow International have said that a major benefit of prefabricated bathrooms was the minimal need for remediation of the pods. Out of 228 pods, only three units had minor defects. This compares to conventionally constructed bathrooms that risk numerous defects as a result of the multiple trades needed on-site.
111 Dixon under construction
The use of offshore-sourced pods at 111 Dixon has gained a lot of attention with an almost continual stream of visitors to the site since they were first loaded in August 2018. At time of writing, 216 bathroom pods had been lifted into the building and total of 192 pods were completely installed. Arrow International’s video of the bathroom installation has gathered 8,000 views on LinkedIn and hundreds of likes and comments.