Unpainting a Courtyard
How decisions made in the mid-20th century caused unintended effects today
Knyff and Kip’s architecturally and topographically accurate engraving of Wytham Abbey — published in Britannia Illustrata in 1707 — shows a collection of buildings arranged around two courtyards.
A century later, the southern courtyard disappeared during Thomas Cundy’s major alterations, while the northern courtyard, which was initially a space surrounded by a grouping of separate buildings, evolved — through in-filling and extension — to become a true quad with a relatively tight sense of enclosure.
Unlike all of the building's main outward-facing elevations, which are built with limestone, the walls of this small courtyard were constructed with brick; later, in the 20th century, white paint was applied. In late 2021, Dr. Duncan Phillips noted in his survey of the building that the paint, which was the wrong type, was causing damaging moisture retention.
By late summer 2022 we had begun the paint removal with a gel-like product which works by softening the coating to a water-soluble residue. The paint itself proved relatively easy to remove, but unfortunately it became evident during the work that other, even more problematic — and indeed tenacious — coatings had been applied in the postwar period. One is bitumen-based and the other is Snowcem, which is thin cement in paintable form. As Darren McLean, a building conservator, says, “Snowcem is white cement, which is harder than normal grey cement. I wouldn't use a cement-based paint on anything you care about.”
As The Society for the Protection of Ancient Buildings (SPAB) writes, “Much of the guidance given by the SPAB concerns the 'undoing' of well-intentioned but ill-conceived work carried out from the mid-20th century to historic buildings. Such work has frequently involved the replacement of lime renders on external walls with highly unsuitable modern cement coverings – a serious time bomb.” So why has cement been so widely used in historic buildings? As the SPAB notes, its use was often well-intentioned – cement is extremely hard and (initially) waterproof, and the belief that this hardness is beneficially protective of the much softer underlying brick or stonework was, and remains, stubbornly widespread. And convenience doubtless also plays its part – compared to lime, cement is easy to mix and work with, and it is very fast-drying too.
In February 2023, we began to explore how to remove the Snowcem with Jody Wyatt of The Breathable House, whose specialism is lime plasters and renders for historic buildings. In his brief report, Jody describes how the removal of the Snowcem — which we agree is essential for the building’s long-term health — will itself damage or even remove the outer fire skin of the bricks, exposing their softer internal mass, then accelerating their deterioration.
Jody’s proposed solution is that after the Snowcem is removed the brickwork be covered with sacrificial lime render, and we’re happy that this pragmatically balances the many factors in this knotty project, whose roots extend to some well-intentioned but misplaced decisions taken six decades or so ago — a common theme whenever cement is present in a historic building. In the next stage of this work, we'll ensure that the local authority’s conservation officer, and Historic England, agree with the expert advice we’ve received so far.