The Deanery and Treasury are on the eastern range of Tom Quad, built in 1525. It was built of Headington stone, much of which had eroded and suffered from heavy sulphate damage.
The elevation was steam cleaned then washed with nebulous water sprays. The stone was then surveyed. The main problem was extensive spalling that had been exacerbated by previous repairs in Roman cement, which were removed. Selected stones were replaced, including a number of mouldings and, particularly, ashlar stones. Hartham Park Bath limestone was used for replacement.