By recommendation, we were asked to provide an underpinning scheme for these two grade II listed cottages on the Crown Estate in Windsor.
These cottages had previously been repaired with masonry reinforcement, however, due to the shallow nature of existing foundations, the clay subsoil and adjacent vegetation, the movement persisted.
Due to this continued movement, a piled raft was required. This entailed the removal of the existing floor, reduced level dig and temporary works to support the superstructure. All of which allowed us to install a piled raft under the entirety of the original structure.
Uncommon for turn of the century properties, these cottages were built with cavity walls. This did not become a commonplace architectural feature until after the war. Adding to this increased width, these cavity walls also feature an external plinth. This meant the external walls of the primary structure were much wider than is traditionally seen and required additional support. Customarily, we would only need to install one stool per position, instead, our engineers designed a double stooling scheme in these areas. This involves two stools being installed adjacently, to prevent any risk of collapse to the superstructure or external plinths.
Piled Raft Design
Our engineers designed a 300mm uniformly thick slab on 16m deep piles of 250mm diameters. Due to the clay subsoil and mature vegetation so close to the properties, 160mm of Clayboard was allowed for under the slab as an anti-heave precaution.
One of the main challenges of this project for our engineers was the rear projection. Due to the exceptionally narrow design, access was limited and the end rooms were not wide enough for our mini- rigs to operate once through the door. To tackle this our engineers extended the raft to the exterior of the building, with piles supporting from outside the superstructure. This avoided any internal walls needing to be demolished to allow for the rig, allowing our client to maintain the properties to the utmost degree.
Treesafe was the ideal solution for this site because it minimised the amount of excavation needed, which was essential due to the close presence of the protected tree. By using a mini rig and hand augering before piling, we could ensure that no tree roots were damaged by the new foundations. Despite poor weather at the time of our works, we were able to continue working without delay.
Ben Wallace, Contracts Manager
The Comdeck product is such a simple but effective method. From design through to completion Abbey Pynford offer a second to none service with excellent health and safety.
Colm O’Boyle, T&B Contractors
Abbey Pynford’s system worked brilliantly for this project. They were quick, tidy and reduced our programme.