Precast Basement, Tunnel and Pool Shell for the Cooper Residence in Oxfordshire

Case Study, March 2026 / Year of project 2025/2026

Glatthaar Keller Precast Basement

Tunnel and Pool Shell for the Cooper Residence in Oxfordshire

The Cooper project began with a clear ambition: to transition from a thoughtfully

constructed home that met the standards of its era into a highly sustainable,

architect-designed home that o;ers exceptional comfort while upholding strong

environmental performance.

Long committed to green living, the clients wanted a house that generated more energy

than it consumed, integrated seamlessly into its woodland setting, and preserved the

mature trees that defined the site.

A key early step was the creation of a precast concrete basement, tunnel and pool shell

engineered and installed by Glatthaar Keller to house the plant equipment, pool and the

technology needed to manage everything. The basement provides a highly insulated,

airtight foundation for the indoor pool and the wider energy strategy, enabling the clients

to realise their vision of a zero-energy, carbon-negative home that combines

sustainability, comfort and architectural quality.

 

The Technical Challenge

The Cooper project demonstrates how a fully precast basement system can streamline

the delivery of complex below-ground structures, even when multiple functional zones

must be integrated 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 already 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 9.60 m by 4.80 m with a standard internal height of 2.68 m.

From this space, a tunnel extended to a separate pool box measuring 5 m by 8 m,

housing an internal pool of approximately 4 m by 3 m. 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 240 mm reinforced concrete walls,

120 mm insulation, and combined Type A and Type B waterproofing.

 

Manufacturing and Installation Timeline

Construction followed Glatthaar’s established sequence. The basement, tunnel and

pool slabs were cast first, followed by the walls and ceilings, and finally the external

tanking. All three 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 20 m 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 250 mm

ground-bearing slab for the house. Glatthaar Keller coordinated closely with Baufritz,

the pool company and RM Construction. The pool contractor later installed all 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 250 mm ground-bearing slab for house

 

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 e;icient on-site assembly

can deliver technically complex basement geometries quickly, cleanly and with minimal

impact on the surrounding community.

 

“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.“

– Colin and Trish Cooper

 

The start and preparation of the groundworks

 

Excavation and foundation stage, Z-shape visible from above

 

Precast panels being craned into position

 

Installed walls and visible Z-shape

 

Finished slab handover point to Baufritz ready to assemble the house

 

House being erected on the Glatthaar foundations

 

Near-complete house with solar panels