A precast basement, tunnel and pool shell in Oxfordshire
Glatthaar Keller's precast, eco friendly basement space for the Cooper residence
The Copper project began with a bold ambition: to start from a blank page and craft a highly sustainable, architect‑designed home that delivers both comfort and exceptional environmental performance.
The Cooper’s had long been committed to green living, wanting a house that generated more energy than it consumed.
They also wanted it to be integrated seamlessly into its woodland setting, preserving the mature trees that defined the site.
What was the process?
An early step of the project was the creation of a precast concrete basement, tunnel and pool shell.
This was engineered and installed by Glatthaar Keller, with the view for it to house the plant equipment, pool and the technology needed to manage it.
The basement provides a highly insulated, airtight foundation for the indoor pool and the wider energy strategy.
It enables the Cooper’s to realise their vision of a zero-energy, carbon-negative home offering a combination of sustainability, comfort and architectural quality.
Photo: Glatthaar Keller
The technical challenge of the project
The Cooper project demonstrates how a fully precast basement system can streamline the delivery of complex below-ground structures.
Even managing to integrate multiple functional zones into a single build sequence.
Designed by Baufritz and the pool contractor, the scheme required Glatthaar Keller to engineer and construct three connected elements: a plant-room basement, a linking tunnel and the outer shell of a swimming pool structure.
Although the architectural concept was fixed, Glatthaar was responsible for structural calculations, production drawings and the complete precast delivery. The team also constructed the ground-bearing slab.
The design
The basement measures 9.60m x 4.80m with a height of 2.68m.
From this space, a tunnel extended to a seperate pool box measuring 5m x 8m, housing an internal pool of approximately 4mx 3m.
This Z-shaped configuration was unusual for Glatthaar, as such facilities are typically integrated into a single basement volume.
Nevertheless, the geometry was accommodated within the company’s standard AquaSafe system, using 240mm reinforced concrete walls, 120mm insulation and a combined type A and B waterproofing.
The Glatthaar Keller precast walls manufactured off site and the L shaped basement. Photo: Glatthaar Keller
Manufacturing and installation timeline
Construction followed Glatthaar’s established sequence, with the basement, tunnel and pool slabs cast first.
This was followed by the walls and ceilings, and finally the external tanking. All three of the structures were erected in one continuous operation.
The precast elements were manufactured in just three days, cured in the factory and installed on site within another three days using a 120-tonne crane positioned 20m from the building line.
With excellent ground conditions and unrestricted access via a private road, the installation phase was straightforward and caused minimal disruption to neighbouring properties.
Overall, the basement, tunnel and pool shell were completed in four weeks – followed by three weeks of backfilling and a further three weeks to construct the 250mm ground-bearing slab for the house.
Glatthaar Keller coordinated closely with Baufritz, the pool company and RM Construction.
The pool contractor later installed all the internal linings, equipment, pipework and ventilation within the tunnel prepared by Glatthaar.
- Weeks 1-4: Basement, tunnel and pool shell installation
- Weeks 5-7: Backfilling operations
- Weeks 8-10: Construction of 250mm ground-bearing slab for house
Precast walls showing prefabricated panels. Photo: Glatthaar Keller
Quality assurance
The project was delivered with a 10-year structural and waterproofing warranty covering the basement, tunnel, pool shell and ground-bearing slab.
The Cooper residence illustrates how factory-controlled precast production and efficient on-site assembly can deliver technically complex basement geometries quickly, cleanly and with minimal impact on the surrounding community.
Colin and Trish Cooper, the clients in this projct, added: “The Glatthaar team and Thomas Salomon have always been very professional and did an excellent job for us.
“We had quite a complex set of foundations with an indoor pool, cellar and tunnel linking the two.
“But Glatthaar just made it seem easy, even though it was not – the sign of true professionals.
“It was also always good to work with the build team who were always friendly and kept the site clean.”
Baufritz house being erected on top of the Glatthaar foundations, showing project progressing to above ground phase. Photo: Glatthaar Keller
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