Think Brick

No perfect match: wall of a church in Breda in original Belgian white stone (below) has been completed with much more sharp-edged Reffroy limestone. (Photo: Wido Quist)

Architects engaged in restoration projects should choose their materials more consciously, says Dr Wido Quist in his PhD thesis.

Many of the churches and cathedrals in south-western Netherlands were built with white Belgian sandy limestone, which was mainly imported during the 14th and 15th centuries. Nowadays, however, only the occasional lump of this limestone is found as a by-product of sand mining. Meanwhile, the old churches erode, their extended parts, like statues and tympana, especially so, and need to be repaired or replaced. But with what?
Sandstone cannot be used because of a law (Zandsteenbesluit, 1951) prohibiting the use of this stone, as it poses a health hazard to workers. Sandstone’s fine dust, created when the stone is being processed, is said to cause silicosis, or ‘dust lungs’.

As a PhD student, Dr Wido Quist (33), of the faculty of Architecture, researched the selection process for restoration materials in four historic buildings over long periods of time – the entire 20th century. Dr Quist wanted to know the reasons why specific materials had been chosen; however, often there was no documentation available about the choices of materials. Moreover, it seemed that external circumstances had dictated the choices, such as, for example, when supply routes were cut off during the First World War, or a building contractor simply preferring to use up his old supplies first. In later years, the choices often seemed to be based on fashion or faith in the claimed quality of a stone, like its durability. Nowadays, it’s mostly Portland limestone, imported from the UK, that’s being used. However, when the Portland is used to complete a structure originally made from Bentheimer sandstone, the Portland sticks out against the grey and weathered Bentheimer like a sore thumb.

Dr Quist argues that the restoration architect is responsible for the choice of materials, and that choosing the materials shouldn’t be a matter of taste or convention. Instead, he argues, one should make explicit choices about colour, texture, historic unity, aesthetics and durability. A simple table in his PhD thesis should make this decision-making process more transparent.

Wido Quist, ‘Vervanging van witte Belgische steen – Materiaalkeuze bij restauratie’, 14 February 2011, PhD supervisor Professor Rob van Hees.