This sloping plot, previously the site of a single property, has been re-designed to include three new-build homes. Due to the underlying highly shrinkable clay, a piled solution was needed. By recommendation, we were offered the opportunity to propose a foundation scheme for this interesting site.
The primary challenge of this project was operating on a terraced site. The level changes from the site entrance to the bottom unit were significant, posing the issue of rig access between terraces.
Working on a terraced site
To tackle this, we proposed the use of a smaller midi rig, our 13.5 tonne Klemm 709. Larger rigs would not have been suitable given the physical dimension constraints of the terraces and the potential for inducing slope movement. The 709 allowed our piling crew to install the piles easily and safely, positioned away from any slopes and accessing each level using ramps designed for the lightweight rig.
Design for a sloping site
The next challenge was to design a scheme that accommodated the different levels between slabs while keeping costs down.
Our engineers employed two large downstands on the second and third units. Totalling over 2.3m high, these downstands were designed to incorporate our patented Brick Support Units (BSU). These allow brickwork to be laid from the base of the downstands, creating an attractive brick wall finish and insuring the slab edges were not left exposed. Using downstands also eliminated the additional work of excavating and installing separate retaining walls between the properties.
The other foundation option considered was a piled beam scheme. However, by opting for Housedeck, our client avoided the extensive and unnecessary challenging work of excavating and installing deep beams on a sloped site. The use of the Housedeck foundations took away the additional operational challenges due to the amount of excavation and spoil removal. As well as avoid the increased costs and potential stability issues associated with Pile and Beam foundations.
Protecting surrounding trees
The choice of using the Housedeck system was also influenced by the requirement to prevent damage to the surrounding trees. This was achieved through designing an optimised number of smaller diameter piles installed by a lighter rig, to minimise the damage due to piling. Housedeck also reduced the damage caused by excavation due to the design requiring a nominal sub-slab void and the BSU edge detail.
“Abbey Pynford were a pleasure to work with on this rather challenging site and their design, management and site staff were all courteous and professional in every way making the difficult work seem much easier than it should have been. Sometimes a challenge is easier tackled head on with a good team behind you and that certainly was the case here.”
“We would recommend them to anyone and would certainly use them again.”
Paul Beeks, MD, Beeks Building Contractors and Developers