A beacon of sustainable reuse built using reclaimed timber groynes

The Durley Chine Environmental Hub is a showcase of sustainable design using repurposed timber. Comprising a Passivhaus education building, a café kiosk and public toilets, this visionary building was designed by TDUK members Footprint Architects and WSP for BCP council.

On the promenade of one of Bournemouth’s popular Blue Flag beaches, the Durley Chine Environmental Hub sits in perfect harmony with its surrounding landscape. Its gently twisting roof, on which native plants grow, echoes the undulating movement of both the water’s tide and the sloping hills behind. The irregularity of the raking columns that prop up its canopy roof is reminiscent of driftwood washed up on the shoreline.

These poetic formal cues are deepened by the Hub’s material expression of its coastal environment. Weathered timber groynes (previously used as sea defences) are used extensively in the decked area and the exterior of the main building. The decking itself is also reclaimed (basralocus) timber – taken from a decommissioned German submarine base. The kiosk and toilet blocks are made from striated layers of concrete mixed with locally sourced sand, emulating the grading of the sedimentary cliff face.

A building to embody the council’s eco ethos

Images © Richard Chivers. The 2-storey Passivhaus block is built from CLT and insulated with recycled newspaper. The brise soleil at the front is made from timber groynes.

Before, the site had contained a temporary lifeguard station on the cliff, a delipidated concrete toilet block and some beach huts. These small structures sat just to the west of the council’s holding yard for waste and debris removed from the beach.

Seeking to renew the site’s function as a municipal compound for waste transfer, BCP council wanted to create a sustainable, multi-function building that would include welfare provision for staff collecting waste and an education venue to support their wider aims of reducing litter and single-use plastics along the seafront.

In response to this brief, Footprint Architects drew on their thirteen years of experience working across Passivhaus and fabric-first housing, sustainability-focused work, school and community spaces, and refurbishments of old buildings. “All this,” project architect Mike Ford explains, “has shaped our practice culture, so that reducing what we do and reusing what’s there has become our mantra.”

Ford recalls that the Footprint team began by asking themselves what a truly sustainable design would be. “The answer would usually be to reuse what is there, but this time we didn’t have a suitable existing structure to work with.”

Breaking up the brief

Instead, Footprint’s approach became focused on streamlining the design by reducing the creation of unnecessary indoor, heated spaces and maximizing the use of recycled and natural materials. A determining move was separating the highly diverse functions of the scheme into a series of smaller buildings; allowing each space to be most efficiently paired with its thermal and energy requirements. This meant that the new toilet block could be unheated and the building fabric uninsulated, while the welfare and education space could be triple glazed and highly insulated. The café seating and exhibition area would be provided for in the sheltered outdoor space created by the canopy roof, tying the whole scheme together.

The old rebar and concrete toilet block was ground down and reused as part of the piling matt for the new building’s foundations, and the cliffside lifeguard station was removed and the land rewilded.

The evolution of a low-carbon timber structure

WSP were the structural and MEP engineers, and their early involvement meant that they were able to shape the Passivhaus goals of the project and help reduce the design’s embodied and operational carbon.

As they started to develop the structural design of the canopy roof, both Footprint and WSP knew that they wanted it to be built using timber. Various approaches were being considered in terms of efficiency when the team came across a large council-managed stockpile of timber groynes just along the beach from the site. This discovery set in motion what would become the defining material intention of the project.

Reusing old marine timber

Previously used to protect local beaches from erosion, the better-quality groyne timbers were already earmarked to be sold to the Environment Agency. Ford explains that it was because they were happy to use the unwanted pieces – “with bolts, screws, holes and knots” – that they got approval for usage from the council.

From there, a multistage process of assessing, selecting and grading the timber was undertaken with the help of BM Trada. Once they knew the lengths and thicknesses of the available stock, the design of the canopy, as well as of the cladding and louvres, was adapted to correspond to the spans of the wood.

There was concern, especially on the part of BCP, about the remaining life span of the reclaimed timbers. As they had already completed one use-life in the water, it wasn’t possible to know, absolutely, how much durability they had left. Lead structural engineer Ben Moss explained that for structural components that would be well protected this wasn’t a problem – such as the rafters supporting the roof. But for the uprights and primary roof structure, it was decided to use 21 tonnes of sustainably sourced new ekki: an intervention that provided suitable reassurance to the client.

Overall, 45 tonnes of reclaimed groyne timber were used to create the secondary structure of the roof and the substrate of the decking, as well as some parapets and the (non-structural) cladding on the education building. Great effort was taken by WSP to minimise unnecessary resizing and machining, and ensure that as much strength was derived from the groynes as possible.

FSC-sourced ekki – known as ‘iron wood’ for its high strength and durability – forms the primary structure of the roof. Exposed connections allow the canopy to be demounted in the future.

Constructing the oversailing roof

The new 100% FSC-certified ekki for the canopy’s primary structure was sourced from Holland, where the pieces were designed and cut by Dutch company Hupkes Wijma before being transported by ferry and road to the site. The hyperbolic roof design meant that each post and beam, and many of the brackets and plates, were individual, and each pre-drilled hole had to be in exactly the right place for the pieces to fit together. Metal fittings were made locally in Poole, with a sample of each bracket and post sent to Holland to make sure the holes would fit.

Benefits of an in-house contractor

The roof going up – with new and reclaimed timbers. Image © Seascape South.

The project was delivered by Seascape South, the in-house construction team for BCP. Having previously worked on numerous projects along the seafront, and with experience delivering Passivhaus and timber buildings, Seascape South were well placed to meet the specific requirements of the Durley Chine construction. Their early involvement in the project – having been brought in from design stage 3 – and close relationship with the client and design teams meant that Seascape South were able to help develop the design and ensure the implementation of challenging aspects that might otherwise have been compromised – namely the significant use of local coastal materials and the sustainable sourcing of the ekki.

Now open to the public in all its silvered, salt- and sand-blown glory, the hub is an inspiring example of environmentally conscious construction, and a demonstration of what can be achieved through collaborative inter-disciplinary partnership.

Design for circular economy

Looking towards the end of the building’s lifecycle, Footprint considered ease of deconstruction and ability to recycle materials. The canopy roof is constructed with exposed fixings so that it can be unbolted and removed. The offsite-fabricated Passivhaus building is able to be disassembled and, in theory, reused elsewhere. It utilises screw-fixed cladding for easy removal, and formaldehyde-free plywood for the internal panelling which can be recycled.