Case Study – Anstey Hall Barns
This project involved the conservation and refurbishment of a group of historic barns to provide eight luxury conversions and a further four new homes on the site. The barns have been carefully designed and restored to blend seamlessly with their environment, staying true to their historic timber-framed structures. The new build parts of the project use CLT and simple building technologies, using local and reclaimed materials that are sympathetic to the original buildings, both visually and practically, without resorting to pastiche. It was an ambitious undertaking, given the dilapidated structures, dating back to the 17th and 18th centuries, with Grade II listings on some of the timber framing. This, together with the planning constraints of working in a conservation area, meant the project was looked on as high-risk and the site had sat empty for many years. The team’s collaborative approach, using innovation and advanced digital design and construction, brought significant benefits in design, programme and budget de-risking the project and making it feasible.
Applying digital techniques to conserve the barns, we have retained more original features than would have otherwise been possible because of the high level of understanding of the buildings and complex structures. Point cloud scanning allowed us to model the complexity accurately in 3D and so not over-simplify solutions. The site team recorded the condition and repairs to the historic buildings photographically through 360 Field, and tagged these to the 360 Glue models. This captured vital data for ongoing conservation, maintenance and future adaptation ensuring historic sustainability as well as enabling the speedy resolution of complex conservation issues and allowing timely approvals by the conservation officer.
Our model-based approach ensured that clear communication achieved maximum collaboration between the design team, client/contractor, supply chain, planners, conservation officers, neighbours and end users. This was essential in getting to grips quickly with a project already underway (the project already had planning permission) and using new technologies.
Early use of 3D models greatly facilitated communication of the scheme to potential residents. Hill were able to better test furniture layouts and produce marketing images encouraging early commitment with most of the homes sold off-plan.
Combining BIM Level 2 protocols with new technologies such as Point Cloud surveying, Autodesk BIM360 Field, Glue, Docs and Point Layout software, all design elements were digitally tagged. This allowed the contractor to take accurate subcontract and materials procurement directly from the model, thus reducing waste, costs and time.
Completed on time and on budget, the project not only transforms derelict agricultural buildings into high quality housing, but also demonstrates that digital design and construction are as applicable to complex conservation projects as to large new buildings.
“ Having gone some way to prove that the technology is wholly beneficial on this complex refurbishment project, we have developed processes for production and delivery of all future housing schemes.”
Mike Beckett – Director, Hill Bespoke
From an early and very clear EIR, we were able to establish BEP that could achieve the client’s very ambitious goals for the project.
The client was clear that a primary goal was the quantification of materials/construction elements in order to:
- Gain better control of the procurement process and avoid the costs associated with ‘lump sum’ subcontracts where quantities risk is transferred to the supply chain for a premium.
- Reduce cost and waste in the material ordering process.
We used seven effective techniques to improve the project design, delivery and operation.
- Extensive point cloud surveys – Raw laser scans were used by the architects to develop ‘as existing’ models as a starting point for the project. This permitted the forensic architectural and engineering design approach that the 8 unique existing buildings demanded.
- Cost Management – Subcontract procurement was facilitated using the common data environment 360 Docs. This was the first project in Europe to use 360 Docs and the team’s feedback has been incorporated into the product.
Key advantages experienced include:
• A faster procurement process
• Time saved by better communication
• Better coordination and scheduling benefits
The contractor / client undertook quantity take offs directly from the federated design model. This required the components within the model to be named and numbered in a structured way that was agreed in advance in order that the bills of quantities could be generated quickly.
In turn this allowed the team to firm up construction budgets more accurately and earlier and then de-risk subcontract procurement by avoiding inefficient ‘lump sum’ sub contracts.
All quantifiable elements were parted and converted to enable quantification using Navisworks. Site manager’s use of Navisworks has speeded up material requisitioning and saved time and money – especially as it did not require employing a separate quantity surveyor.
The supply chain members were brought in early to share and review models and discuss the elements they would be involved with. This informed the design significantly. In several cases, we were able to use suppliers’ BIM components such as sanitary-ware, lighting, kitchens, door components and windows, driving efficiencies and providing additional data to the model.
BIM made it easy to extract work-in-progress information that was used to get early stage costing and specialist input into details such as the external windows, curtain walling and doors. This enabled better, more coordinated design, reducing the likelihood of value engineering at a later stage.
We also shared models on Glue with Carpenter Oak and Woodland (Joiners) who used the models to tag and track the work they did to the existing timber using ‘before and after’ photographs attached to the Glue model. These were, in turn, shared with the Conservation Officer as evidence in discharging the listed building and planning conditions.
We also believe that there has been a reduction in wastage by eliminating the need for extra material to compensate for the inaccuracy of traditional material take-offs.
“Procurement to all of the sub-contractors would typically take around 6 months, however we will have managed to halve this time. Since Hill are taking the risk on the quantity information, we are finding that more sub-contractors are coming back with prices, and they are taking less time to do so.”
Mike Beckett – Director, Hill Bespoke.
- Clash avoidance – In addition to the usual coordination of the architecture, MEP and structure this project presented the challenge to coordinate with complicated existing structures. The existing historic timber frames have moved and bowed considerably over their lifetime, the model based approach de-risked the insertion of new structure and fabric.
- Visualisation – We were able to clearly communicate to all stakeholders using the WIP model in Navisworks or over the cloud with 360 Glue. This encouraged confident and timely decision-making. The model was also processed and used for marking purposes.
- Construction setting out and verification – was enabled through Autodesk Point Layout. Digital setting out points were embedded in the design model and shared over the cloud through the CDE. This drove the equipment on site that was used to set out the location of the new buildings and new elements within the existing buildings, which speeded up the process and improved accuracy. The system was also used in reverse to verify locations in the field and push them back into the design model.
- Programme management – BIM 360 Field software was used to manage and track all actions and deliverables for both the design and construction teams. Sub-contractor procurement was also managed through 360 Field. It was then used to manage the quality control checklist for trades on site ensuring standards of quality and giving a clear audit trail.
- Facilities Management Data – New homeowners are receiving iPads preloaded with the Model of their home, allowing them to log faults and provide post occupancy feedback.
Hill were able to control material ordering and avoided premiums associated with estimating and ordering along the supply chain. There are also the usual benefits to design, programme and cost. Best practice modelling processes and techniques have been established for use on projects going forward, and there have been benefits in marketing and customer engagement.
Timely approvals by the Conservation Officer were made simple with new technology. The site team recorded the condition and repairs to the historic buildings photographically through 360 Field, and tagged these to the 360 Glue models. This generated a comprehensive report on the works undertaken and, without the need for site visits, concerns were addressed and the programme protected.
Receiving an iPad with an ‘as built’ model of the property, homeowners have full information about their property allowing them to flag queries and feedback to Customer Care. The model will be used for efficient future operation and maintenance of the buildings and has full conservation information embedded into it.
David Miller Architects
The processes developed on Anstey Hall Barns have been integrated into the office’s ISO accredited Best Practice Management System for use on future projects.
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