Terracotta, magic dust and cracks at Cardiff Central Railway Station

Cardiff Central station is the Grade II listed main railway station in Cardiff (and thus the busiest in Wales). It’s historically valuable as the single best example of a mostly intact mid-war station. It’s the architectural equivalent of a common toy that is a collectors item because all of the accessories are still in the original packaging. It was built 1932-1934s using Great Western Railway’s kit of parts – so despite appearance it’s a steel frame building with a thin stone cladding. The platform buildings and subways are predominantly terracotta: glazed doultonware with cast signage that has outlasted some of the platforms!

There’s a few elements of interest to the designer. Terracotta, being a hard brittle material, is vulnerable to chipping on the sharp edges. Fortunately, terracotta blocks before they are fired are soft and carvable, so its possible to shape and shape them to go around a curve. The radius of the curve isn’t really big enough to improve eyelines or crowd flow, but it does neatly make the corner more resilient. (not perfectly, there’s some poorly replaced tiles at the bottom). It’s a nice design detail. Other minor design defects include the grey mortar leak just visible at the top from the platform retopping, and the anti-slip/bottom of stairs marker.

Lets have a look at the detail of the station platform buildings.

Don’t you love that false arch keystone detail above each window frame? And then along the bottom, the left is an integrated flat arch over the door, the right just merges back into the wall. Nearly every block in that photo is different! That brown dirt is very characteristic. It’s very fine iron oxide dust from train brake pads. It’s magnetic, clingy, UV proof, It is such a long lived, persistent stain that I’ve heard it was a reason British rail chose red-brown for the livery, just to hide the omnipresent dust! In theory, since this is glazed terracotta, the iron oxides should wash right off with rain, but this area is well sheltered under the canopy, but high enough that no-one really wants to get on a stepladder (by a railway) to sponge it down. It would be interesting to try and identify surfaces differences for why some of blocks show much more than others. The canopy was recently repainted, so it may be just inconsistent access for the cleaning.

Below is a composite photo of another station building shows ‘the kit of parts’ a little more. On the left there’s a small intermediate canopy support truss, with the steel column buried in the terracotta. On the right there’s a bigger arched truss landing on a little plinth that (presumably) ties straight back into the steel stanchion behind the terracotta. If you take a closer look at the top of the picture, there’s clear cracking across the entire top, with slightly more around the ‘C’. The doorway that used to be on the left (lintel detail as previous photo) has been closed up with nicely chosen reproduction tiles. I’ve outline the best guess at cracks on the lower detail. Some may be water tracks. If I had to guess, I’d say the central portion of wall is settling slightly, but that is a low confidence guess.