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A conversation between the artist and Deborah Lazarus, a structural engineer who worked in Arup’s Advanced Technology and Research group. She was involved in the assessment of a number of historic buildings in the path of Crossrail’s tunnel project, including the House of Saint Barnabas.
Navine G. Khan-Dossos: We both share a fascination for architectural structure, in your case from an engineering point of view, and mine from that of a mural painter. How important are your eyes, and what you see in front of you, in comparison to the readings and measurements you take using tools?
Deborah Lazarus: My eyes are certainly important. As structural engineers we tend to notice buildings in our surroundings—both their ‘positive’ features (which may of course be subjective) but also unusual aspects that may well include defects. I think it is always really important to use both visual information and also anything else that may inform the building’s behaviour. Readings can be misleading or even wrong on occasion and unexpected results need to be interrogated. Facades facing south, for example, may show movement during the day due to thermal effects even without ground movements.
NGKD: The Drawing Room is the ornate and fragile centre-piece of this building, which is why I chose to situate the paintings here. Could you tell me a bit about the damage assessment work you were involved in at the House of Saint Barnabas, and how this differed from the several hundred other historic buildings you had to review along the Crossrail 1 route?
DL: The House of Saint Barnabas is Grade 1 listed. It has notably ornate plasterwork and is acknowledged as a fine example of a Georgian interior. The house has been extended and altered over the years and has a lot of history associated with it.
A detailed condition survey was undertaken prior to work commencing. The survey was carried out by the House’s own specialists and provided an extensive photographic record for comparison on completion of the works. It captured of course that some degree of cracking and other minor defects existed at the outset—hardly surprising in a building of this age! This identified a few areas where preemptive mitigation works were recommended. These were undertaken before any works were started.
Extensive monitoring instrumentation was also installed. In addition to items such as prisms and tilt meters, and also hydrostatic levelling cells in the basement, instrumentation was installed below the floors to check more localised movements and devices were used to check any ‘lozenging’ of the Drawing Room which might lead to cracking in the ceiling plasterwork.
While other listed buildings were assessed and monitored in accordance with Crossrail requirements and agreements with local authority conservation officers, it is probably correct that the House received more attention than most if not all of the others. The Rev Dr Adam Scott, chair of the building committee, was significant in ensuring that it received detailed review and protection at all stages.
NGKD: Calibration targets are a major focus of my work, and always attract my eye when I’m visiting sites and monuments. I’ve seen the same laser targets on the Parthenon in Athens as I have in Soho, London. They inhabit a place between function and aesthetic, particularly when they are left behind and are no longer used. Do you place any aesthetic value on these markers? Have you ever thought of them as beautiful? Or as an eyesore?
I think markers left behind may have different stories. They tell us that at some stage—and we may not know when—someone was interested in what was happening to the building. These could be level markers, crackmeters, simple glass tell tales etc. They suggest that at some point in the building’s history there has been some kind of problem, or potential problem.
They may also leave a record of how the building was assembled, or even who did the work. Examples are the carpenters’ marks on timber members, as well as stone-masons’ marks. I see these as part of a building’s history that become part of its fabric over time. We should see them as something integral to the building and not simply as functional technical devices.
NGKD: Is there any consideration as to how these markers play an aesthetic role in the life of the building? In terms of where they are placed, their size, or colour?
DL: For Crossrail they were installed where needed to provide the best information and with the understanding that they would be removed on completion of monitoring. There is not much choice in colour or shape/size I think for a given function. They need to be visible and easily read whether manually or automatically. If it is intended that these should be left as a permanent record of this phase of the buildings life, or for future monitoring, then perhaps this could be an avenue to explore.
NGKD: So could you imagine a time when these markers and structures could be incorporated into the design of all buildings of the future so that they were already in place? A sort of pre-empting of future movement or instability? How would that look to you?
DL: There are obvious benefits in embedding sensors of some form as well as information about the structure such as material grade and specification, or the date of construction. The latter would perhaps encourage future reuse of the elements as their history would be clearly available and this has been under discussion.
NGKD: Are these marks and targets something you notice when you walk around cities? Do they tell you a story about the buildings that an untrained eye might not pick up on?
DL: I probably tend to notice marks and targets—although not necessarily all of course—as part of my general interest in buildings and other structures. These suggest that there has been some problem or potential problem in the past which someone has thought should be kept under observation. We may not know what or when this might have been but it is an additional facet of the building’s history. We have just been hiking in Maine. There is a particular type of marker cairn used on the trails and I found myself wondering what people in the future might make of these strange small structures which could perhaps be thought of as ritual stones. What will future generations make of the things that we leave behind?
Deborah Lazarus is a consultant at Arup having worked there for many years as a structural engineer working on all aspects of existing structures, with a particular focus on heritage-related work. Her fields of interest and expertise include the maintenance and re-use of historic buildings: she has spoken at national and international conferences and has published a number of papers on this subject. She is currently a member of the Historic England London Advisory Committee.