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Time lapse of modular eco-building built in Green Unit’s factory

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Watch our time lapse video below and read on to find out what’s involved in the offsite build process of our ARC eco-friendly, modular buildings.

This time lapse video shows the offsite construction of our 109sqm* ARC II building for The Vindolanda Trustan archaeological UNESCO World Heritage Site in Northumberland.

* Gross Internal Area

 

 Read about the new Archaeology Centre for the Vindolanda Trust.

The stages in the ARC offsite build process

The entire offsite build process for the ARC II for Vindolanda took just a few months – and when it was delivered it was installed at the client site in just six days. 

We designed and built Vindolanda’s low carbon, modular building in 5 road-transportable sections in our Oxfordshire factory.

 

Modular component fabrications and steel base frame

Component fabrication of ARC modular buildingThe ARC build starts out with timber component fabrication whereby drawings for the component pieces for the floor, wall and ceiling modules of our buildings are neatly ‘nested’ onto panelised timber boards.

The boards are then fed into CNC (computer numerical control) machines for precision cutting, routing and drilling. The CNC cutting process ensures high levels of accuracy as each component piece is cut to within half a millimetre tolerance of the component drawings - which makes the assembly stage in the build process highly efficient.

Alongside the component fabrication, the steel base frame and internal steel frames are assembled at our main offsite factory on our 6-acre site in Culham within the Oxfordshire Science Vale. Our wider building - the ARC II - requires an internal steel frame to support its wider span. 

Find information on the technical specifications of our ARC buildings here.

 

Timber frame construction

Timber frame and steel subframe of ARC modular buildingIn the next phase of the offsite build, the floor, wall, wall window, and ceiling cassettes are assembled using bespoke, curved jigs. The cassettes are then built onto the steel base frame to construct the building’s shell. At least 230mm of high performance wood fibre insulation is snuggly fitted into the floor, wall and ceiling cavities. The ARC II  Vindolanda building shell was completed in a matter of weeks, with the team working under cover of the factory throughout the winter months. Production timelines can however be flexed depending on the level of labour resource deployed.

The Vindolanda building has floor to ceiling glazing at both ends of the building, with one fascia end recessed to mitigate solar gain. The glass fascia is fitted in the later stages of construction (once the building's main shell is in place).

 

Waterproofing and cladding

External cladding in progress on ARC modular buildingWith the main structure built and all external and internal doorways and wall windows mounted, the waterproof and breather membranes are installed by our specialist roofing contractor. As the building is designed and built to be delivered in five transportable pod sections, the building needs to be separated mid-way through the build to allow the weathertight seals to be fitted at the connection points between the pods.

The external cladding – a thermally modified, sustainable, British Poplar - is then applied. So that the building can be transported to site in individual sections, there is a thin shadow gap between each pod-section. The finish on the interior walls is a painted, redwood cladding – the interior cladding is installed with the primer and undercoats, and the topcoat is sprayed at a later stage in situ.

 

Internal fit-out

With the build quickly coming together, the internal elements of the building are fitted out. This includes Mechanical Ventilation Heat Recovery (MVHR) units, airtightness membranes, bespoke internal cabinets and kitchenette units, and underfloor heating mats.

First and second fixes for all electrical and plumbing inside the building are carried out during the offsite build. There are very high-quality electrical male and female connections within the floor, wall and ceiling cassettes between each pod section. This means that when the building is delivered to the client site for installation, the electrics are simply a case of ‘plug and play’ which minimises the time we need to spend onsite. 

 

Pick-up, delivery and installation 

ARC modular section ready for deliveryOnce complete, the building is finally split into road-transportable sections, ready for transit. Robust, reusable covers are placed on both sides of each pod for protection during delivery and installation. Each pod section – in the case of the Vindolanda ARC II building, weighing about 8 tonnes each – is crane-lifted onto an articulated lorry. The lorries transport the sections of the ARC building to the client site (usually overnight) and the sections are craned into place over the course of the following day.

As we aim to complete 95% of the build offsite at our factory premises, there are just a few elements left that can only be completed onsite. The roof must be completely sealed for airtightness and waterproofing, and the green roofing is then installed. Internal flooring is laid, and a custom-made rubber seal is put in place to internally seal between the pod-sections. Connections are made to electricity and water services, as required. Finally, airtightness testing and Building Regulations surveys are completed.

Find out about sustainable, modular buildings for visitor centres and retail spaces