Yet another example of Roman skills can be found in their understanding and use of stones to create foundations for buildings and some very large buildings that still stand today on what we consider to be ‘ancient methods’. In fact the Romans were ahead of us in many aspects of construction techniques.
Roman foundation construction didn’t use tonnes of concrete like we do today, damaging our ecology by ripping up acres of the earth for quarry stone and then releasing millions of tonnes of carbon into the atmosphere when we ‘cook’ it.
Roman cobble was their answer to distributing loads and providing a solid base for heavy buildings. By using river and sea washed tumbled stone, they would excavate a trench (as shallow as 400mm) and fill the bottom with larger cobbles, then infill any voids with smaller cobbles, then bind it with sand and clay. The next layers would be similar, using smaller stones to infill voids and a final slab over the stone/sand/clay foundation.
Imagine a large box with footballs in the bottom, with the gaps in between filled with tennis balls, and the smaller gaps between them filled with ping-pong balls and then marbles, all then all in-filled with sand and clay.
Cobbles were so valuable and of course difficult to transport it was common to dig out some existing buildings foundation and pinch the stones for a new building and modern archaeologists have christened the voids that were left ‘robber trenches’.
The long abandoned rubble (cobble) trench foundation was brought back to life and popularized by Frank Lloyd Wright in the late 1800’s and early 1900’s. Rubble trench foundations utilize rubble and loose stone in a similar way to the Roman method but also to improve drainage. The method is rarely used today.