PROJECT SUMMARY

Commissioned by Triodos Bank, this new office building embodies the clear investment values of the occupying organisation, creating a 21st century workplace with a long-term view of resource ownership and value.

Three compact towers are connected by a shared plinth at lower levels. Above a concrete basement, cores, floor and roof elements are CLT with sculptural glulam beams and columns radiating from around the cores at the centre of the upper floor pop-ups.

FIG 20.1 BIM view illustrating central cores and plinth below upper floor workspaces. The structure above ground floor slab is predominantly CLT with glulam columns and sculptural beams.

Mostly glazed externally with a flush curtain wall, a priority was creating a high-quality internal environment. A limited palette of materials is used alongside exposed timber elements with glulam columns and beams and CLT expressed to cores where vertical CLT panels form lift shafts anchoring other elements and to soffits, with screening from decorative timber elements and soffit-mounted service panels. CLT was also used for stairs and roof slabs.

Beyond the structural solutions, all CLT panels and major materials used were considered in terms of design for disassembly and maximum value reuse from the outset. This is a bank building that is also a materials bank and a very deliberate investment for the future: a great example of a low-impact building that reflects circular economy principles as well as any built to date.

FIG 20.2 CLT floors are partially masked by timber ceiling level ribs that allow access to chilled/radiant panels and services fed from risers within the CLT cores beyond.

PROJECT AMBITIONS

Minimising the carbon footprint of the building was a concern for the project team and as such, concrete use was limited to basement areas due to the proximity of ground water – it is never good practice to use CLT below ground level. Elsewhere, structural elements are virtually all mass timber. Glulam beams span from central cores creating generous floor heights and emphasising a free-form facade with full flexibility for glazing, shading and opening lights where required, maximising daylight penetration and visual connection to the surrounding woodland setting.

FIG 20.3 Four storey height panels were used to create stability cores and vertical shafts.

FIG 20.4 Once lifted into position, vertical panels require propping only until neighbouring panels are secured.

FIG 20.5 CLT shafts are typically better aligned than those made of other materials due to extremely tight tolerances and allow rapid fixing of lift installations and services.

EARLY COLLABORATION

From the outset, a collaborative approach was adopted to maximise potential gains and best address technical issues. Having previously worked for the same client, the architect and many of the team were brought together at the outset with construction advisors, the contractor and its subcontractors. This has been acknowledged as a key factor in delivering what is a ground-breaking building, in terms of initial construction, timber performance and future potential for demountability and maximum-value materials re-use.

FIG 20.6 CLT stability core and shafts with glulam columns and beams before the installation of first floor CLT slabs. All timber fixings were designed to be demountable and recorded (down to the last screw) to maximise future value and potential reuse of elements and materials.