HMP Millsike showcases a platform approach to concrete MMC

HMP Millsike is a new prison (main works contract value £400m) being built by Kier with precast concrete specialists PCE for the Ministry of Justice (MoJ). It is situated on a 53-acre site near York.  Due to open in 2025 is an excellent example of the Government Construction Playbook in action.  The project maximises Modern Methods of Construction (MMC), digital techniques and value for the local community, in line with the Playbook commitment to better, faster and greener delivery and is an excellent example of Design for Manufacture and Assembly (DfMA) using precast concrete.

The new prison will provide c.1,500 Category C resettlement places for adult male prisoners, providing a rehabilitative environment and preparing them for release. It will run solely on electricity, making it the first of its kind in the UK. Solar panels, heat pump technology and more efficient lighting systems mean it will use 68% less energy than even the most recent new build prison, HMP Fosse Way.

Precast Concrete Platform Solution

Reinforced concrete is an obvious choice of material to provide the durability and security necessary for a safe environment for prison inmates and staff. Like its predecessors, HMP Five Wells and HMP Fosse Way, HMP Millsike adopted a DfMA approach using precast concrete for the structure which included external and internal walls, floor, stairs, frame and ground beams.

The project utilised more than 16,500 precast components, manufactured in nine factories across the UK and Ireland. The performance of this robust supply chain, brought together by contractor PCE, was facilitated by an established UK precast concrete industry which in turn makes use of locally and responsibly sourced mineral products.

The platform approach with standardised installation methodology and common connection principles enabled the predictable and precise installation of 50,000 tonnes of concrete structural components, installing up to 220 tonnes daily. The bespoke moulds ensured consistency in manufacturing custodial components, integrating structural ties builders work openings, and cast in  M&E items.

The structure, for each houseblock within the prison, was installed in an average of 12 weeks by just 12 operatives, and completed in 46 weeks. With offsite manufacture removing many high-risk activities of site installation, including reductions in working at height and eliminating onsite hot works/drilling, PCE were able to achieve 200,000 RIDDOR free hours.

The Playbook in practice

Harmonise, digitise and rationalise demand

The blueprint for HMP Millsike is based on the design for HMP Five Wells, a new men’s Category C prison in Wellingborough, Northamptonshire that was successfully completed by Kier in November 2021. HMP Five Wells has won more than 15 industry awards, including for productivity and pioneering offsite techniques.

In line with Playbook principles, the project is demonstrating consistent, measurable improvement between the two projects.  This includes Monitoring Pre-Manufactured Value (PMV) with monthly reports to the client and currently achieving 84.2% PMV

The MMC installation is also showing improvement, measured as 15% more consistent than HMP Five Wells. This reduction in install time variance has provided additional certainty throughout each stage of the build, for example, providing greater certainty of when next phases will begin.  And despite significant design changes, such as moving from gas to electric heating, there has also been a 26% reduction in Requests for Information (RFIs) and Tender Queries (TQs). This demonstrates the benefits of adopting an established, robust design, with increased standardisation.

Further embed digital technologies

BIM and digital design have been used to enable DfMA, standardise designs and simplify traditional build elements. This has resulted in fewer deliveries, a smaller onsite workforce, reduction in waste, enhanced safety, and certainty of quality and delivery.  This has not only been applied to the concrete structure but also in the use of standardised mechanical, electrical and plumbing (MEP) components, which have reduced hours and operative numbers. A simple switch to press-fit jointing, rather than a traditional threading solution, saved 60% of labour costs. Standardisation will also make it easier to install, maintain and repair these MEP elements in future.

Additionally, HMP Millsike has made use of innovative new technology to create a real-time digital construction twin of the physical buildings. Using Bluetooth tags that connect back to the digital twin, the team can track offsite components from design through to manufacture and installation onsite. This has improved accuracy while reducing costs and saving carbon emissions, by removing the need to check each component at the factory. The automated system is less prone to human error. It has been welcomed by manufacturers and the supply chain and won the BIM/Digital Construction Award at the 2023 Offsite Awards. Use of digital twin technology is central to the Transforming Infrastructure Performance: Roadmap to 2030 and ensures Golden Thread compliance.

Delivery model assessments

HMP Millsike is the first of four new prisons to be built by the Alliance 4 New Prisons (A4NP). This industry-leading Alliance has seen Kier, other main contractors and key supply chain partners, such as PCE, pool their collective knowledge and experience. Together, they have established a shared, standardised and repeatable delivery model that can be used across all four sites. The model prioritises whole life costs, embodied carbon and social benefits.

A4NP workshops led to the creation of 126 Big Ideas, resulting in 355 improvements including use of precast elements and ways to reduce materials and waste. A4NP won the 2023 Collaborative Leadership Award from the Institute for Collaborative Working and is providing a model for other Government programmes.

Effective contracting and  Social Value

In addition to its achievements in sustainability, MMC and digital, HMP Millsike is delivering outstanding results for the local community. To date (as of September 2025)the project has provided 765 new local jobs, upskilling for 724 workers and prospective workers, and 88 apprentices and trainees. It is providing significant support for local businesses, with over 40% of construction orders coming from within 50 miles of the site.

Kier and MoJ are also working hard to create opportunities for prison leavers and those on ROTL (Release on Temporary Licence). This is being achieved through Kier’s Making Ground initiative, designed to support serving and ex-prisoners into sustainable employment within the construction industry. As of September 2024, Kier and their supply chain have provided employment for 36 prison leavers and 36 placements for men on ROTL, including in the installation process delivered by PCE. Kier aim to provide 50 sustainable job opportunities for prison leavers by the time the project is completed. PCE contributed to local communities in other ways too with charitable donations including a local park and gardening community.

Decarbonisation

The focus on decarbonisation across the recent new prisons programme included a Decarbonising Precast Concrete project carried out in 2021 (Akerlof, 2021. Decarbonising Precast Concrete: Tangible Innovation Through Partnership), that focused on establishing commercially viable incremental changes to achieve better carbon profiles.  Building upon improvements adopted at HMP Millsike demonstrated a 24% embodied carbon saving against the established baseline for ‘the precast concrete.  These achievements are now feeding into further cross disciplinary and supply chain collaboration to decarbonise still further.

A blueprint for the future

Driving standardisation across projects allows teams to get familiar with requirements and repeat in subsequent buildings. The platform approach will have long-term benefits for other projects and its techniques are already being adopted by other members of the MoJ Contractors’ Alliance. This will improve efficiency in operation, reduce costs and help the MoJ move towards the decarbonisation of the prison estate. 

But the successes and benefits here also provide tangible evidence of what could be achievable if applied to different type of construction projects – a potential blue print to support other sector transformations.

Images courtesy of PCE

Client: Ministry of Justice (MoJ

Lead Contractor: Kier

Superstructure and façade delivery partner: PCE Limited

Project Manager: Mace

Architect: Pick Everard

 Structural Engineer: Curtins

 M& E consultant: MZA Consulting