With very large properties either side, the basement could not be excavated and constructed in the traditional manner. As a result, the perimeter of the basement firstly saw the installation of sheet piles, 80 metres in total, in order to support the ground and neighbouring houses. The Piling was carried out by specialist piling contractor, who worked with Beautiful Basements design and construction teams to install these piles 10 metres into the ground
Once the piling was in place, the challenge of installing 80 metres of reinforced concrete capping beams to the entire perimeter of the basement began. This capping beam was installed prior to the main dig beginning, to restrain the sheet piles from flexing at the top under the pressure of the ground the outside.
Next, the main excavation began, removing some 250 lorries of soils away from the site. The dig had to carried out in two parts, stopping half-way down to formation to install a set of hydraulic rams to the perimeter up against the now exposed piles. These rams, again, provided the additional strength required to ensure the piles did not flex from the middle. Once the hydraulic rams were in situ the dig commenced once again, this time going down to the formation level where the slab could be constructed.
From there a very complex basement was constructed with multiple levels, an elevator shaft, foul pumping stations, garages, patios and a swimming pool, all constructed in reinforced waterproof concrete walls and floor. Finally, the pre-cast concrete ground floor was laid in place to allow the main, above ground build to begin.
Waterproofing for the project was comprised of two systems to comply with 3rd party warranty requirements;
- Integral waterproof reinforced concrete walls and floor
- Internal cavity drainage membrane, linked to two pumping stations