The "calade"

Surfacing with slabs does not appear to have been used before the 2nd century B.C. Until then roadways were surfaced with sand or pebbles.

It was the Romans, who were excellent builders and colonisers, who created the modern land based routes in order to enable speedy travel across their Empire.

The oldest paving known is that of the Appian Way (296 B.C.) between the Porte Capena and the Temple of Mars, a distance of one mile, which was extended in the 2nd century B.C. This route was surfaced with large slabs of lava at the exit to Rome.

Experts in the period tell us that in places where there was only pedestrian traffic, as around the Forum and the public areas, the surface was constructed with thin stone slabs, resting on a very carefully prepared and levelled base made up of a draining layer of gravel. Where the traffic could have resulted in the ground being churned up, the slabs were very much thicker, 30 to 50 cm, and bedded down onto one or several layers of pebbles, gravel or sand. Evidence of this can still be seen at archaeological sites such Pompeii, Ephesus and Glanum.

Within private areas, in town, the Romans used marble, ceramic mosaic and brick for the surfacing of the ground and walls. In ancient times, in the Middle Ages and still today, internal areas are of flattened or limed earth. Sometimes a soft lime, perhaps coloured, mortar gives a finished appearance to the surfacing. Where marble powder has been added, it is called stucco.


The characteristics of the old roads

The roadway was surfaced with slabs, which are long stones called calade in Provence, but only on those sections where the traffic was heavy or the presence of water would have resulted in the creation of a quagmire.

The other reason for paving a roadway was to facilitate traffic circulation in steep areas or even to demonstrate riches. Roadways were often paved close to monuments and at town gates.

The width of the paving was not subject to any regulation. At Vaison-la-romaine, the old road measured 4.5 m in width. Secondary and rural roads were, up to the start of the 19th century, 1.50 m to 4 m wide. The paved width did not, at times, allow two carts to pass.

The remnants of stone paving remaining in Provence illustrates the excellent quality of the constructions. The wheel tracks worn into the roadway with no disturbance to the embedded surface is evidence of the great care taken in its construction.

These paved roadways were nor intended for high speed travel, rather to enable traffic circulation in all seasons.

In Provence a calade is a roadway paved with long stones, placed vertically with their sides facing upwards.

 

The construction of a roadway

Technical recommendations for the preparation of the ground can be taken from chapter 1 book VII of the work by the Roman author Vitruve. These rule remain, broadly, valid today for the reconstruction of the traditional calades. According to Vitruve, the first thing is to put in place the statumen (a dry gravel footing). Next spread a layer of lime, sand and pebbles or gravel, which is a thick concrete: the rudus. Finally, a tile mortar as the base of the surfacing, this is the nucleus.

The preparation of the ground is essential to ensure good flexibility and enable even compression of the roadway while still providing drainage of the run off water.

Surfacing consists of a collection of stones placed dry and edgeways, sides facing up. The stones need to be placed very tightly together and well embedded into the bed of sand. The choice of surfacing stones is dependent on the local geology. There are slabs of sandstone, limestone, lava and schist. Stones must be frost resistant and have a smooth surface, not be too angular or have too prominent ridges. Stones, which are too round, are unsuitable as they are difficult to wedge in the sand.

In Provence and in the Forcalquier region, the calades are of limestone drawn from stone clearing of the fields or rivers. The border stones, which act as stretchers to block the roadway are made up of large stones 40 to 50 deep.

Filling between the stones is sometimes a mixture of sand and gravel.

Where there is a significant slope, steps are laid out across the roadway. These are, in general, around a maximum of 10 cm steps which enable the top to be reached. These roadways of long steps with flats 80 cm to 120 cm are called "donkey step" calades. The nose stones of the step, which are subject to lateral pressure, must be deeply embedded, to at least 30 cm.

Large stones placed around the edges of the stones form a block. These stones are called stretchers. The placement of these stones requires particular care. They are selected from amongst the biggest available and some can weigh hundreds of kilograms. A channel for water is sometimes provided between the edge of the roadway and a pavement raised above the level of the road.

 


Examples of the most frequent calade problems

Description of the problem
Cause of the problem
Remedy
Repair techniques for a simple problem
Stones missing
Stones removed,
Lack of maintenance,
Wedging not tight enough
Stones too small, inadequate penetration
Sand bed not adequately packed down
Take up
Relay

Stones loosened

Stone tails not adequately buried
Take up
Relay
Roadway loosened or deformed
Earth movement,
Footing not adequately packed down
Take up
Relay
Roots and bushes through the calade
Lack of maintenance

Clean out,
take up

Weeds encroaching Lack of maintenance Clean out,
take up