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The Fortress Baths at Isca

October 3, 2011

While I was writing my last blog, Roman Plumbing at Isca, I stumbled across something that was relative to an earlier blog regarding excavating at Caerleon. You see, I have found that the port is not first time that tegula walls have been excavated at Caerleon.

Brick that will not stand exposure on roofs can never be strong enough to carry its load in a wall. Hence the strongest built brick walls are those which are constructed out of old roofing tiles.

Marcus Vitruvius Pollio: de Architectura, Book II

Now it starts to make some sense, to me at least, on why there was so much wall construction using ceramic building material (CBM) at Caerleon – quite simply,  it was in one of their construction manuals.

Between 1977 and 1981, the Fortress Baths at Isca were excavated by J. David Zienkiewicz. The culmination of his work are two rather large volumes detailing his findings, and the impressive building preserving the excavated baths for the general public to view today. The first stone building within the fortress, it was constructed around 75AD and testament to Roman construction techniques, it was probably still standing in the 13C when it was demolished.

The building that concerns us here is called the natatio. This was an external pool holding some 80,250 gallons of water and measuring 135 feet in length. The shallow end measured 4 feet and this shelved down to 5 feet at the deep end. There was evidence of a fountain house at one end, constructed during the first phase, but this was demolished when the natatio underwent quite radical alterations about fifty years after it was first built.

Artists impression of the Fortress Baths at Caerleon

Artists impression of the Fortress Baths at Caerleon showing the natatio and fountain house

The buildings were huge, colossal even. The vaulted ceilings would have been as high as the abbeys that you can still see today. I think that the wall construction of the natatio is best read as the excavator intended.

Above this course, the wall was faced entirely with the flanges of roofing tegulae. None of these tiles were complete, and all were broken so that into a roughly triangular shape so as to maintain the complete length (generally 65cm) of a single flange on the longest side. The tiles were laid in regular courses, with their flanged edges facing upwards and to the wall face, so that their apices bonded them to the mortar core.

Sound familiar? The broken tiles are exactly the same as the port walls described in my first blog on Caerleon. Interestingly he goes on to say;

The tiles were not wasters, nor could accidentally broken tegulae have preserved so many complete flanges. The exclusive use of tegulae for this submerged walling indicates that the material was considered well-suited for the purpose.

Hence my quote from the de Architectura at the top of the page. None of the tiles bore the Legionary stamp which I find unusual, these were in abundance at this years excavations.

Speaking of which I had a very unusual conversation with a student while in trench four one day. The student explained to me that to find a Legionary stamp of the second Augustan Legion was on their preferences list. Ok, the student was young, incredibly focused but I like to find what I find, not what I want to. Nevertheless, I joined in. I explained that I would prefer to find a stamp of the Legio XX Valeria Victrix. This comment produced a very puzzled face for the student. It confused them. Flustered may be a better a word. An hour or so later we walked back from lunch. I asked if my statement had been talked about by their fellow students, it had, and all of them were in disagreement with what I had said. Asking if they were betting people, something I normally do not succumb to, I was told that they were. Now I had a moral dilemma, do I make a shed load of money by betting them five pounds each that I was right, or do I leave them be? I settled for the latter and I am not flushed with money by any means.

Usk also housed a Legionary Fortress. Unlike Caerleon, it was Pre-Flavian and built C55AD. By C64AD it is assumed that the Fortress was occupied by the XX legion. But the student(s) would not buy this train of thought. The Usk excavations were huge and they really help our understanding of the downfall of the Silures – the Iron Age tribe of the area. Systematically demolished after just 20 years it has been suggested that the timbers from the fort were then floated down the river Usk to be used at Caerleon.

As you have probably realised, there is the connection. The first stone buildings at Caerleon were the Fortress Baths – built using tegulae, the port was built using tegulae, was the port built prior to the baths or are they contemporary in date?

Its a big question, only the dating material for trench one may help us understand that.

I think that is enough of Italian Holiday Camps in Wales for now.

My next blog will be Medieval, back to the Cistercians, perhaps.



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