Small amounts of water (e.g. surface run-off or boggy ground) were dealt with by means of drainage channels in the base of the curtain wall. Permanently running water would be channelled through culverts, like one noted at Denton Burn by Collingwood Bruce. Major rivers, such as the Eden, Irthing, and North Tyne were crossed by bridges large enough to carry a walkway and, later, even a road. What is not known is how the openings were blocked to prevent intruders getting through, although some sort of wooden or iron grille is a possibility.
Fragments of the curtain wall with what may be whitewash are known, as are collapsed sections of what appear to be rendering. Examples of rendered walls are known from the Roman world, sometimes scribed and painted with red lines to look like ashlar masonry, sometimes just painted.
However, the evidence for Hadrian’s Wall is by no means clear-cut, and so-called examples of whitewash could easily be due to leaching of lime from mortar whilst the rendering could be a type of pointing known as ribbon pointing. Examples of the possible types of external finish of the curtain wall are displayed on the west end of the reconstructed wall at Wallsend: ribbon pointed, rendered and scribed, rendered and painted, and whitewashed.
Further reading: Breeze 2006
Popular reconstructions that show soldiers patrolling the top of Hadrian’s Wall have a powerful effect upon the viewer, but it is worth asking what evidence exists for such an interpretation of the structure of the curtain wall. Frontier walls are known in Tunisia and southern Germany that never had walkways on top of them.
Hadrian’s Wall is certainly broad enough to have accommodated a walkway with a parapet. Chamfered stones from an external string course have been identified as being a decorative feature associated with such walkways, as at the legionary fortress at Chester, and such stones are known in relative abundance from Hadrian’s Wall. The existence of steps at Milecastle 48 and possibly Peel Gap tower are important circumstantial evidence for the use of a walkway too.
If the Wall had a walkway, it will almost certainly have been crenelated.
Crenelations are the indentations atop the battlements of a fortification. They enhanced its defensive capability so much that, in the medieval period in England, one needed a ‘licence to crenelate’ from the monarch. A crenelated parapet enables a defender to shelter behind the merlon (the higher part) and shoot or cast through the crenel (the gap between neighbouring merlons).
Roman crenelations are depicted on Trajan’s Column and survive embedded in the walls of the Castra Praetoria in Rome, as well as on the city walls of Dura-Europos in Syria. Other archaeological finds indicating their use (notably merlon caps and parapet footings) have been made in Britain, from the legionary fortress at Chester. No indisputable archaeological finds are known from the Wall, although the Rudge Cup has a stylised crenelated design on top of what appear to be turrets.
Scholars have long argued that Hadrian’s Wall was not used as a fighting platform and so the issue of the existence or not of crenellations on it has been a contentious one. The most important point to note about crenellations is that, if they were indeed used on Hadrian’s Wall, they imply the existence of a walkway.
It is thought that the men garrisoning the milecastles and turrets came from the neighbouring forts. We know the Roman army frequently practised outposting throughout the empire, which meant that any fort or fortress might have detachments of varying sizes sent off on various tasks. This is confirmed by the Vindolanda writing tablets – a strength report of the last decade of the 1st century AD (so about 30 years before the Wall) reveals that cohors I Tungrorum had 60% of its men outposted, rather than at Vindolanda itself. So, although direct evidence is lacking, it is likely that the forts provided the men for manning the Wall.
Further reading: Breeze and Dobson 2000
There is no clear answer to this question and we do not even know if men lived in turrets, or merely used them for cover and for signalling during patrols of the Wall. Hearths in turrets show that some form of occupation, perhaps even cooking, took place there, but its permanence is a matter for debate. It seems reasonable to assume that each milecastle was responsible for the neighbouring turret on either side, but that is only an assumption.
Turrets have been reconstructed as both flat-topped with parapets and roofed with a peripheral balcony (see figure above), the latter doubtless influenced by representations of signal towers on Trajan’s Column. Occasional finds of roofing material have been made in the vicinity of turrets but not enough for there to be certainty over this.
Further reading: Symonds and Mason 2009