21 Arlington Street, designed by James Leoni and overlooking Green Park in central London, was built in 1740. It helped establish the area as a centre of London’s society, and since its construction, it has been the home to dignitaries such as Lord Middlesex, the Duke of Dorset, Lord Weymouth and the Marquess of Bath, Earl Gower, and the Earl and Dowager of Sefton.
Today, this historic building houses offices and particular care had to be taken with the refurbishment to ensure the character and original features were kept.
To ensure the original brickwork facades were maintained Harrison Waterproofing used Köster PUR Gel from Delta Membrane Systems for all vaulted ceilings and earth retaining walls.
Design Manager and Group Director Simon Harrison said: “When I was approached to help with the scheme, my original suggestion was to use the Delta membrane system along with a specialist render to cover the exposed brickwork.
However, the conservation officer working on the scheme was keen to ensure the original brickwork was maintained, so we then had to find a system that would meet this tough demand.” Simon discussed this with technical experts at Delta Membrane Systems, who suggested various options from Köster – specifically, Köster PUR Gel. Delta call this method of making the structure as watertight as possible prior to fixing the Delta system ‘locking down the structure’.
Walls and arches in the cellars of the building are built in brickwork with mortar joints varying in width from 5-20mm. The arch brickwork at the entrance to the cellars has mortar joints varying from 5-8mm.
To allow the use of a modified 13mm injection packer suitable for gel injection, holes were bored at 350mm staggered centres, with a frequency of 10 bore holes per m2. Work included a combination of ‘area’ and ‘curtain’ injection for the vaulted ceilings.
This method was preferred because it created a waterproof gel membrane at the back of the brickwork, filling any voids within the surrounding clay. It also fills the voids within the mortar joints, ensuring a robust, durable waterproofing solution.
Highly skilled bricklayers were called in to create new openings in the vaults that would complement the original brickwork. Again, the Köster product was injected behind these openings.
Köster PUR Gel is a solvent-free, water-activated polyurethane gel. Depending on the amount of water added, a highly elastic, waterproof hydro-gel is formed. After it has reacted in dilutions of up to 1:7, it is resistant to pressurised water. It does not contain free isocyanides and is chemically stable after reaction. It does not contribute to corrosion and does not emit groundwater polluting substances.
Koster PUR Gel
Delta System 500
Harrison Waterproofing was subsequently listed as the preferred specialist when a main contractor was sought. Simon Harrison explained: “As this is a new system to the market, there was something of a ‘learning curve’ that we had to go through in the application work, and there was the occasional need for re-injection to ensure the hidden side of the brickwork was totally sealed.”
Delta Membrane Systems offers a host of damp-proofing solutions for various applications. In this project, Delta has again brought its expertise and high-quality product range as part of the solution to this scheme.