Main ContractorGalliford Try
ArchitectCullinan Studio
Structural EngineerScott Hughes Design
Creating a completely new type of facility for the NHS as well as Liverpool's world leading paediatric hospital, 'Alder Hey in the Park' breaks the mould of the institutional appearance to our NHS landscape, with the architects's vision for the latest phase complementing nature and planting - both inside and outside the buildings - with the sensitive and creative use of engineered timber.

B&K Structures' experience in steel as well as CLT was instrumental in constructing two new healthcare units for the famous children's hospital, alongside one another in a verdant setting, that has been acclaimed as creating a 21st century 'Health Campus' and possible blueprint for future NHS projects. Signficantly, the specialist children's mental health unit and outpatient units have been designed with the biophilic benefits of timber centre stage - a timeless natural material with multiple attributes including sustainability.

The twin buildings - The Catkin Centre and Sunflower House - surround landscaped courtyards with consulting rooms, bedrooms and play spaces, to provide a healthcare setting that simply doesn't look or feel like a hospital. The concept evolved through extended consultation involving both patients and health professionals, with Cullinan Studio being the architectural practice responsible for the initial designs, and 10Architect responsible for delivery.

B&K Structures (BKS) was shortlisted for its pre-eminence in the offsite market and selected under competitive tender to deliver a package which harnesses the biophilic, health, and well-being benefits of wood to help create a landmark healthcare project.


A value engineering exercise had previously led to the original plans for a reinforced concrete structure being switched to one featuring prefabricated steelwork and engineered timber: with BKS's expertise delivering substantial cost savings in terms of speed of erection, predictability and finishing trades, while reducing weight and environmental impacts.

A further benefit of hybrid engineered timber and steel combined structural package was the ability to ensure a reduced number of just-in-time deliveries to a restricted location, compared to conventional construction techniques. This helped maintain a rapid build programme as well as high build quality, with reduced health & safety issues on site.


The final form of the Catkin Centre and Sunflower House presents a truly hybrid design solution answering multiple technical as well as healthcare challeneges, with B&K Structures' comprehensive and multi-faceted package being pivotal to the project's delivery.

As an offsite specialist widely experienced in providing packages which combine a variety of different prefabricated systems, BKS worked with several members of its established supply chain to deliver a seamlessly coordinated solution. This included 223 tonnes of steelwork for the podium at entrance level, which extends to 1,855 m2 of steel decking. The engineered timber encompassed 263 tonnes or 4,379 m2 of CLT from Stora Enso and 15 tonnes or 42 m3 of glulam, with Curzon Clarke Engineering undertaking the installation of all three with the assistance of BKS joiners. BKS partnered with Ramboll to carry out the detailed design of the timber structural elements and connections.

All were enabled by digitalised collaborative design for manufacture and the assembly process, with information exchanged via 3D models between the manufacturer, Stora Enso, B&K Structures, Galliford Try, Scott Hughes, and others.

The self-finished nature of CLT avoids the need for plastering or other wet trades, and although the 'industrial visual' grade of CLT was selected over the residential grade alternative as a cost consideration, the appearance the appearance of smoothness of the surface have been perfect for the application. Meanwhile, precision routing in the factory facilitated the speedy installation of pipes and cables or larger M&E equipment as the fit-out proceeded. Aided by the BIM Level 2 modelling and computer-controlled machining to a tolerance of 0.5 to 1.0 mm, the completed structure achieves the highest standards of accuracy.

The decision to utilise engineered timber as an offsite solution further ensured predictability of cost and high levels of accuracy in thhe factory setting, while programmed deliveries mitigated the restricted site storage facilities and optimised the use of available cranage.

Having B&K Structures as a single specialist coordinating a hybrid package connsolidated responsibility, effectively offering a one-stop shop for the structure, while all component parts were fully identified to speed up the installation sequence. In addition to its strength and accuracy of manufacture, the manner in which CLT is produced with small sections of timber being jointed using advanced formaldehyde-free adhesives, guarantees they offer excellent airtightness: thereby helping to cut heat loss through the building envelope or between different areas of the building.


According to the design team, every design decision relating to the two buildings has been shaped by a concern for reducing stress and promoting positive effects on health and wellbeing. The result is a unique space for healing, which also encompasses a host of wider environmental benefits.

Both embodied and operational carbon have been fully considered, with the CLT elements to the envelope delivering very high standards of airtightness, cutting heating loads within a facility which features a variety of renewable and low energy technologies. As well as PV panels, the two buildings are connected into a central energy hub with a 500kWe gas-fulled CHP and air source heat pumps.

BKS and Ramboll optimised the timber deisgn to keep material use low and wastage minimal, resulting in the project overall containing a total of 668m3 of engineered timber, all of which was sustainability sourced and delivered with a 100% PEFC certified full chain of custody claim: earning maximum points at MAT03 of BREEAM. The greenhouse gases captured in the trees as they grew totalled 508 tonnes of CO2e, while the responsible management of European forests ensures that the timber used on this project can be calculated to have been completely replaced by new growth in just two minutes and twenty-six seconds.

Any offcuts on site are collected and converted into pellets which go to generate heat at the production plant. When the end of the building's life is eventually reached, engineered timber structures are relatively easy to dismantle and re-use or recycle, contributing to a circular economy.

However, in a Healthcare facility, the most striking benefit of engineered timber as the dominant material in Alder Hey's Catkin Centre can be measured in its health impacts. According to Buro Happold: "The design team was able to reassure the NHS that cross laminated timber walls would prove suitable in terms of the infection control needs of a climical setting. Our specialist acoustics and fire engineering teams also fed into the design, helping to reliase a timiber building in this unusual medical setting."


The Structural Timber Awards - Healthcare Project of the Year (2022)

Design in Mental Health Awards - Project of the Year Shortlist (2019)

The project is an exciting opportunity for our specialist community and mental health services to work together to ensure our children, young people and families with complex conditions can access a range of specialist services in a child friendly environment. For our children and young people with mental health and neurodevelopmental conditions, this will ensure that their needs are met in an environment that equally supports both mental and physical health.
Lisa Cooper
Alder Hey's Community and Mental Health Services
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