Oxford Method Research Programme

Foundations

Trial holes revealed that the existing ground had a very high clay content. The foundations were therefore designed as pads and beams with a suspended insitu power-floated slab spanning across the beams. Allowance for future loading from an additional first floor was included.

Existing drains outside the existing building created considerable problems. Some had to be diverted, and others were allowed to pass through the foundations.

Columns

It was not necessary, or indeed possible, for the main structural grid of the new building to coincide with the structural grid of the existing building. The 600mm planning grid was maintained, but the structure of the new building was designed to be completely independent of the existing structure. The nearest columns are therefore approximately 2 metres from the face of the existing building, and the new roof beams cantilever up to this face.

The columns themselves are 180mm square hollow section steel, slightly larger than existing. These are encased in 15mm Glasroc S Frameless Encasement System to give one hour fire protection. Above ceiling level, all structural steelwork is treated with Nullifire System S607 to continue the one-hour fire protection. (The reason for this is explained under "ceilings").

Beams

All beams at roof level are designed to allow for possible future floor loading. The principle of double beams with a gap between for services to pass through was not considered economically justifiable. Single lattice beams were therefore employed, but universal steel beams were used around the perimeter. These allowed air intake and extract ducts to reach the external walls by passing below the beams rather than through them, thereby giving greater flexibility over the size of the ducts and the exact positions for the external louvres.

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