Ground Sun Limited was commissioned to design and build bespoke annex foundations. A structure requiring a robust, low-impact foundation system due to the presence of adjacent trees. The chosen solution: AB Chance Helical Screw Pile foundations. The project entailed designing and installing a reliable substructure for a 17 x 5m annex, with minimal disruption and high structural integrity.
Site Preparation and Preliminaries
To initiate the project, Ground Sun deployed a two-man crew along with a bobcat excavator to clear the site and prepare 13 excavated pockets for piling. This allowed piles to terminate below ground and provided space for cast reinforced concrete (RC) pile caps.
Annex Foundations Design
Pile design was carried out by our Chartered Structural Engineer, utilising Helicap design software informed by local borehole data. This ensured compliance with engineering standards and building control regulations.
Key design steps included:
– Preparation of torque correlation logs post-installation.
– Structural engineering of the steel frame, deck, and pile caps.
– Fabrication drawings to guide the construction process.
Helical Screw Pile Installation
Ground Sun installed AB Chance solid steel shaft helical pulldown screw piles with a 150mm grout column. Piles were installed to a depth of circa 5m, with 2 additional raked piles installed for added stability as the site was on a hill at the edge of a forest. The piles offer an ultimate capacity up to 240kN, with a safety factor of 300%, resulting in a conservative 80kN working load per pile.
This method provided a clean, efficient, and vibration-free solution ideal for sensitive environments.
Pile Cap and Reinforcement
Following pile installation, Ground Sun supplied and cast reinforced concrete pile caps, designed to distribute loads from the annex frame evenly to the pile heads. Reinforcement was designed and supplied to meet structural specifications and site conditions.
Steel Grillage
A custom hot-dip galvanised steel grillage was supplied and installed, including:
– 203x203x46kg/m steel sections
– Tie beams and stub columns
– Estimated 2.5 tonnes of structural steelwork
This steel framework formed the critical interface between the groundworks and the above-ground annex structure.
Concrete Beam and Block Floor
The concrete beam and block floor was manufactured offsite by a specialist company and lifted into position.
Ground Sun successfully delivered technically sound system of cost-effective foundations for an annex within tight timeframes. The use of AB Chance helical screw piles provided minimal environmental impact, high load capacity, and adaptability to unpredictable ground conditions. Client satisfaction was achieved through precise execution, professional design coordination, and sustainable construction methods.
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As an experienced London Piling Contractor Ground Sun delivers precision screw pile installations across London and the South East. Whether it’s a new build, extension, or commercial structure, our screw piling solutions offer you speed, stability, and minimal environmental impact. Get a fast no-obligation quote today and discover how helical screw piles can save you time, money, and disruption on your next project.
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Certified AB CHANCE Helical Screw Pile Installations
As an experienced Piling Contractor, Ground Sun delivers technically robust screw piling solutions using AB CHANCE® Helical Screw Piles. The system is supported by established technical data and can be designed to meet relevant structural and Building Regulations requirements, subject to site-specific engineering design and approval by the appointed Building Control body.
Suitable for both residential and commercial projects, screw piling is particularly effective in urban locations, restricted-access sites and environmentally sensitive areas. Installation data, pile calculations and testing information can be provided to support the design and approval process, helping to demonstrate performance and long-term structural suitability.