It was great to see both familiar and new faces at Friday’s site visit to St Patrick’s Cathedral and St Matthew-in-the-City.
The tour, given by Peter Reed, centred around the philosophy of strengthening iconic buildings. Peter described two contrasting methods for strengthening. The first, which he referred to as the “honest” method, involves adding visible bracing (usually steel) to the interior and/or the exterior of the structure. The honesty of this approach is that the strengthening doesn’t pretend to be part of the original fabric. It’s also more reversible if and when new technology emerges. In contrast to this approach, what Peter called the “concealed” method involves inserting bracing into the fabric of a structure, and then making the insertions as invisible as possible.
St Patrick’s contains both methods–in the main body of the church, steel has been inserted into the walls and hidden. In the tower, which some site visitors scaled, the steel bracing is not concealed. This is partly because it wouldn’t be possible to create a straight path from the tip of the spire, and partly because this area is not accessible to most visitors. Some of our crew made it into the belfry, though!
Next, the tour moved to St Matthew-in-the-City. (If you didn’t make it onto the tour, and you’ve never been there, do yourself a favour and drop in there one day. It’s simply stunning. I don’t believe there’s anything like it in this country. When you go, GO INSIDE.) Structurally, says Peter, the building is identical to a Gothic cathedral of the 12th through 15th century — apart from the Portland cement mortar which holds the blocks together. And herein lay the crux of the talk–how on Earth can we strengthen something as unique as this? “Honest” bracing would have to be pretty exceptional to escape severely defacing the building, and “concealed” bracing requires extensive drilling, which would be ground-breaking, very tricky, potentially in contravention of heritage principles, and, last-but-not-least, outrageously expensive. In fact, best practice might be to do nothing and wait for technology to catch up with the problem, hoping nothing too seismic happens in the meantime.