From The Schommunity Wiki
“What was the function of Hadrian’s Wall?”
Hadrian’s Wall is the most famous and iconic of all archaeological sites in Britain, but what was it for? Most sources will tell you it was for defence, but from whom? And how did it work? Why did the Romans invest so much effort in something that they abandoned before it was even finished!
Use the links below to research these questions (and post some of your own!)
The Roman Empire and Roman Frontiers: 
Wallnet Education Web Site: 
Britain Express: 
Life of Hadrian: 
Hadrian Quiz: 
Elements of the wall system (from North to South)
The Forward Ditch
This was in the standard V-shape of a roman military ditch. In the bottom was a small square slot, known as the ‘ankle-breaker’ - but is that what it was really for? What other function might it have had? In one place (Limestone Corner – pictured) the ditch had not been finished before the Wall was abandoned and the army moved north. In other places, along the Whin Sill ridge, there are long sections where the wall runs right up the edge of the cliffs and there is no forward ditch at all.
‘Berm’ is a military term to describe a flat open area between a ditch and a wall. How did this fit into the system as a whole? Was its purpose military or purely practical? Why does the wall not sit directly next to the ditch?
The Romans were famous for their roads and Hadrian’s Wall is no exception! This road ran parallel to the whole length of the wall. Yet the main east-west road across England from Newcastle to Carlisle (the Stanegate) lay just to the south. So why was it essential to have two roads? The photo shows the best preserved section of roman road in the UK – on Wheeldale Moor in North Yorkshire.
Running parallel to the wall to the south was a mysterious complex of banks and ditches called the vallum. A broad flat ditch flanked to both north and south by parallel mounds of earth and turf. Was this a defensive structure? Who was it defending? And from whom? The pictures show a stretch of the vallum as it is now (near Carrawburgh) and one of the vallum crossing points (at Benwell, Newcastle).
The ‘Broad Wall’ section
When building work began on Hadrian’s Wall it was originally 3 metres wide at its base. Building work had started and the foundations for a large part of the wall had been already laid when this width was reduced. Archaeologists disagree about why this might have happened and whose decision it was.
The ‘Narrow Wall’ section
Soon after building work had begun, the width of the Wall was reduced to just 2.5 metres. In some places it is even less. In some places turrets had been built with ‘wings’ to bond them into the wall on the old width gauge. At the same time there was a lot of building work on new forts. Does this give us a clue about the relative importance of the wall itself within the whole Hadrian’s Wall scheme?
The Turf Wall section
The western end of Hadrian’s Wall is very different in its construction to the familiar image of a stone barrier. This section of the wall system is 40 roman miles (61 km) long and was built of mounded-up turf. It was probably topped with a wooden walkway. Turf walls cannot be made with vertical edges and so this would have been tapered, or ‘battered’, inwards from a wide base. The picture shows an excavated cross-section through part of the turf wall section. It is 6 metres wide at its base.