On site at 188 Randolph, Chicago

Randolph Tower in the Loop, Chicago, is undergoing the largest ever removal and replacement of terracotta. Mark Kuberski, Central Building and Preservation, the Contractors on this almighty project, was kind enough to give me the grand tour of this 45 storey skyscraper.

With hard hats donned, we made our way to the site office, where Mark introduced me to some of the team and explained the scope of the project. The 1905 drawings by the original terracotta manufacturers Northwestern Terracotta have survived and will not only save a lot of time and money in surveying work, but also provide a fantastic historically accurate point of reference for the project going forward. I met Brett Laureys, Project Architect with Wiss Janney Elster Associates, the  the next day who showed me the work being done to reinstate as accurately as possible the ground floor terracotta and huge shield motif above the doorway, using archival photography and the drawings. I look forward to seeing the finished article as it promises to be wonderfully recreated.

We spent some time studying the plans and Mark explained how the blocks on the building were numbered in sets and within each set every piece identified. Central Building has created a spreadsheet which then correlates each set and how many times it repeats throughout the tower, giving total numbers of each block.

20,000 blocks have been identified as requiring replacement. Some will be removed and re positioned, others can be pinned to secure them, rather than be removed. Each block has been assesed and identified on the drawing and this information collected in the spreadsheet. A large number are of course sound and repointing is all that is required.

Up we went to the base of the octagonal tower that extends from the bulk of the builidng. Mark explained how the building has been at risk for some years and new owners are now thankfully restoring and converting the building to residential apartments. Although the sales market is quite depressed in Chicago as it is across the US and in England, the rental market is buoyant, particualy for desirable apartments in central locations such as this. The loop trains rattle their way literally outside the the 2nd storey windows! ChicAgo.

All blocks that needed to be removed on this portion of the tower now have been, and good progress was being made in reinstating those marked for going back up. Gladding McBean have been receiving all relevant samples and are hard at work making the blocks for replacement. My tour of Gladding McBean still seemed a way off at this point but I relished the opportunity to the same job from site to manufacture. I would see the blocks coming through Gladding McBean when I got the the West Coast before the first ones were due to arrive on site early in October.

With relief that I wear sensible shoes, rather than dress to impress, to meetings, we scrambled out onto the scaffold to take a look at work in progress:

You can see, above, blocks being replaced. Steel that is exposed is cleaned and painted to protect it from corrosion. Moisture ingress is the main cause of deterioration to terracotta. Corroded steel can expand by up to 6 times its volume, this expansion jacking causes cracking and damage to the terracotta. Once cracks start to appear more moisture gets into the steel frame causing more corrosion and the problem worsens rapidly.

The horizonal plate that you can see above replaces the old roughly cut steel plate. The new are laser cut to fit the profile of the terracotta block of that particular section. Flashing is used to protect the steels wherever possible (green coverings in the left photo). The image below describes how terracotta is fixed into the building using pins and anchors, as such work to be started halfway up, without any material supporting it from below.

Some terracotta is being replaced by alternative material, GFRC (Glass Fibre Reinforced Plastic). I found this surprising considering the scale of the project and the amount of investment evident. Each one of these panels (below) replaces several terracotta blocks. So by having one large repeating  panel made in GFRC rather than terracotta, the cost saving is large. Mark assured me of the attention to detail in colour matching and the process by which this material had been signed off. I find it hard, however, to think of this as anything other than a false economy. I imagine on a job of this scale, however, there must be some compromises.

There are 2 colours of terracotta on the building – the majority is a dry sand cream coloured glaze with several different textured effects. The second is a dark iron glaze, with a speckle to it.

The darker finish is found in decoration around the windows and in the mullions. It is a clever metallic, matt glaze and will certainly fool a few people on the ground into believing its metallic disguise.

The tower is gothick styled with vines, small creatures and faces embellishing the ogee window forms and blockwork.

I am very grateful to both Mark Kuberski and Brett Laureys who talked me through the project. I’ve worked with terracotta for so long, and having seen so many important and exciting sites in Chicago and across the States, it really has crowned my experience to see such detail on site.

Stay tuned to see the replacement blocks being made at Gladding McBean’s facility, from clay pit to glazing, firing and packing.

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