A key planning condition for this iconic renovation project was the repair of 348 linear metres of river wall. Today, flood defences that date back to the 1850s are showing the ravages not only of tide and time but of an infestation of buddleia, which has overrun a significant stretch of their length. Aggressive and invasive, this perennial shrub outcompetes native vegetation, taking a vice-like foothold in walls and causing deep, extensive damage. Producing up to 10 million highly dispersible seeds each winter; once established, buddleia is extremely difficult to eradicate.
The services of London-based property restoration expert Thomann-Hanry were enlisted to tackle the seemingly overwhelming task of eliminating the buddleia and rebuilding the damaged river wall. Undertaken in the past, mere pruning was not an option – cutting the plant back simply results in stronger root regrowth the following spring. Instead, a more robust and complete solution was called for. After cutting back the foliage, marine eco-safe herbicide will be applied, destroying an extensive dual root network that runs both horizontally and vertically across, through and behind the facing bricks. The entire root system will then be cut out of the wall, before all surfaces are cleaned under pressurised steam to ensure that all seeds (which can lie dormant for up to 10 years before germinating) are totally destroyed. The river wall comprises a one-and-a-half brick-thick English Bond, clad over the original Roman cement wall installed by the Victorians. The height of the wall has increased at least twice over the years.
Once the buddleia has been removed and the delaminated and damaged bricks carefully cut away, the wall will be sympathetically repaired using imperial size bricks to match the original. For additional strength, Thomann-Hanry has commissioned a small batch of marine grade stainless steel ties to retain the bricks and ensure the works will last for the next 150 years or more. This is no job for an ordinary bricklayer, as Thomann-Hanry is using a specialist mortar which cures skin-hard within 30 minutes. The mortar has been matched to the original, and small batches are prepared each week by Cornish Lime for "just in time" delivery, as the product has a short shelf life compared to mass-produced cement. Sourced from a location in the Alps, the lime continues to cure hard underwater as the tide rises without being washed out. No additional chemicals are added to the mix as Thomann-Hanry is obliged to protect the marine ecosystem and avoid doing anything that could affect this delicate balance.
In preparation for the project, staff were trained to commercial operator standard for working on the Thames – this included a professional responsibilities course, a VHF radio course, a rescue course and a boat handling course. The survey and safety boat was purpose-built for the project by Ribcraft in the UK. As the vessel has to be commercially registered as a workboat, safety features were only implemented after lengthy consultation with the Port of London Authority marine surveyors.
Thomann-Hanry Managing Director, Mark Styles, commented: “By making it a dual-purpose vessel, we are able not only to take the client and third parties to view the job and discuss the works close-up but also to photograph and survey from a very stable and agile platform. There has been considerable interest in the boat and, as a result, we expect to carry out future surveys for clients using this as a platform.”
A mammoth undertaking in a site of great historic importance called for a unique blend of equipment, coordination and expertise. With the entire length of the river walls to be surveyed by Concept Capture 3D software, augmented by reality mesh CAD, high-end supercomputing hardware capable of processing multiple terabytes of data was essential. The challenging tidal riverside environment ruled out conventional scaffolded solutions, so access could only be by way of agile truck-mounted platforms, supported by a licenced floating dock, site safety boat and survey vessel. In order to collaborate effectively with seven key authority stakeholders and coordinate a project of such extraordinary complexity, highly experienced management capabilities were an absolute prerequisite.
Above all, the project demanded extensive and wide-ranging expertise in sensitively restoring and repairing historic and heritage sites of global importance. Having worked on some of the world’s most famous buildings, from the Louvre and the Kremlin to King’s College, Cambridge, The Ritz and New York’s MetLife skyscraper, Thomann-Hanry brings not only the expertise, but all the hardware, equipment and management skills required for such a key element of the iconic Battersea Power Station redevelopment.