Projects cont'd

The location of Whitelands House at the Sloane Square end of Kings Road, Chelsea, is one of the most prestigious in London. Set next to the Royal Hospital and the Duke of York's Barracks, it is close to the shops and restaurants in Knightsbridge and Belgravia as well as Chelsea, and is also within easy reach of Battersea Park, Green Park, Hyde Park and Kensington Gardens.

Originally built in 1936, Whitelands House comprises 120 luxury apartments in an eleven storey 'X' shaped building. At ground floor level on its Kings Road frontage it also had, as stated in the original promotional literature, "high-class shops, a branch of the National Provincial Bank and an up-to-date car service station with large garage in the basement."

High street closure
The bank eventually became part of the NatWest Group following the merger of the National Provincial with the Westminster Bank. However, recent banking practices have led to more centralisation, with increased use of remote facilities via telephone and electronic card systems. An unfortunate side-effect of this has been the closure of many smaller high street branches, and the bank at Whitelands House became a casualty of this in early 1996.

Being located in such a prime position, however, the building was ripe for redevelopment, and a plan was put together by Martin's Properties, who were responsible for the site.

When converting any property to a potentially high-earning retail use, it is imperative to maximise as much floor area as possible to gain maximum return from investment. One major problem with all banks is that the buildings in which they are housed invariably have secure vaults and strong rooms, usually located in the basement. As would be expected, walls, floors and ceilings in secure areas such as these are extremely thick and are constructed in reinforced concrete. This bank was no exception, the walls and the ceiling above the basement being 500 mm thick. To maximise the retail floor space in the basement, these walls and ceiling would have to be demolished, and this presented two major problems, one being cost and the other the environmental impact caused during the course of the work itself.

Regarding cost, a method had to be developed which would ensure that the floor area 'released' by the demolition would ensure a profitable return within a reasonable amount of time. This was accentuated by the fact that the work itself was very restricted in terms of working space and time-scale, since the concrete walls were not only heavily reinforced, but contained flint aggregate, a particularly difficult material to cut.

The environmental impact was perhaps even more of a problem, since the bank was situated underneath some of the most expensive residential property in London. Disturbance to residents would have to be almost non-existent and allowable working times would be restricted throughout. This precluded the use of conventional demolition methods involving jack-hammers and similar percussive tools.

Minimal noise and vibration
Coincidentally, Martin's Properties had just completed the construction of four penthouses on the roof of Whitelands House. Part of this had involved diamond sawing and drilling for minor demolition works. The specialist diamond cutting subcontractors for this, Concrete Cutters Concrete Drilling & Sawing Co. Ltd, had performed the work very much to Martin's Properties satisfaction, causing very little noise or vibration and completing on time. The two companies, therefore, discussed the possibility of employing diamond cutting methods for this work.

Before commencing, however, it was decided to call in a structural engineering consultant to ensure that the demolition did not interfere with the structural integrity of the building. Croydon-based Andrews, Kent & Stone were appointed to this task, having worked previously with Concrete Cutters on similar jobs. Between them a programme of work was developed which would ensure the job would be completed within the 12 week timescale and would be carried out with the minimum of impact to the residents.

The plan of the demolition is shown in the diagram above. The concrete walls and slabs were removed by a combination of diamond drilling and bursting, coupled with diamond track sawing at the extremities. In areas where space was restricted by structural members, diamond stitch drilling was employed.

SDA Plus Series
Concrete Cutters used Frischmuth + Freitag FF301 drill rigs, with Van Moppes diamond core bits, 107 mm diameter for stitch drilling and 110 mm for bursting holes. A Hydrostress hydraulic burster completed the job. For sawing, Nimbus 750 and 900 mm diameter X182 blades were used in two passes. The core bits and sawblades were fitted with segments impregnated with synthetic diamond abrasive from De Beers SDA Plus Series, the ideal grit for the aggressive lint aggregate, steel-reinforced concrete that had to be cut.

In total, just under 100 tonnes of this concrete were removed from the basement area and the job was easily completed within the 12 week timescale.
The work enabled a basement area of approximately 80 sq. m. to be made available for redevelopment as retail space, thus adding considerably to the profitability of the conversion. And, just as important in this case, no complaints were received from residents or neighbours during the whole duration of the works.

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