Substrate preparation (by intended use)
Paving
Paving can be made of cobblestone or polygonal stone.
Cobblestone is installed in 3 ways:
on a sand bed
on a concrete bed
on a semi-dry screed
The bed for cobblestone depends on expected traffic, both in volume and type – pedestrian or vehicle. Based on this, trenches are dug 5 cm deep for pedestrian-traffic paving beds and 18-23 cm for vehicle-traffic paving beds. The trench is covered with gravel, crushed stone, or aggregate. A sand layer is then spread over the gravel base. It’s compacted, and cobblestone installation can then proceed.
For installation on a concrete bed or semi-dry screed, the base layer is prepared following the same instructions as for flooring.
Substrate preparation for polygonal stone installation is similar to that for cobblestone (the trench is shallower, and polygonal stone is most often installed on a concrete bed).
Flagstones and stepping stones are installed directly on the ground, on a sand bed.
Outdoor paths are meant for pedestrian or vehicle traffic. For pedestrian traffic, slate, marble, sandstone, or granite cobblestones are used, more rarely travertine, in a thin format (3-5 cm, even 7 cm) or polygonal stone; for vehicle traffic, granite or sandstone cobblestones are used, 8-10 cm thick.
Road paving is regulated under Law 10/1995 on construction quality and standard SR 6978/1995. Under these standards, cobblestone is used on streets (including those with major traffic flow) and on roads with medium to fairly heavy traffic, but not very heavy traffic. For heavy-traffic roads, cobblestone over 10 cm thick is used, and for medium traffic, blocks (cobblestone 8-10 cm thick) are used. Under the standards, medium traffic means pedestrian traffic of 3,501-8,000 people/day (400-1,000 people/hour) and vehicle traffic of 4,501-11,000 vehicles/day (3,501-8,000 vehicles/hour), representing two-lane roads.
Building a cobblestone road under the conditions above meets the following requirements:
a single slope for single-lane roads and for two-lane roads separated by a median strip. The same applies to parking areas and squares.
the slope is 2% for streets with a median strip, 1.5-2.5% for squares and parking areas
block paving needs a 2.5% slope
the maximum allowed unevenness is 10 mm, except where this would cause water to pool on the surface
joint width is 5-8 mm
Following these requirements, cobblestone can be installed in 3 ways.
1. On a sand bed – the standard, most commonly used option
Drainage conditions are checked – it’s essential that water doesn’t pool under the stones, so how water flows across the surface must be checked
A drainage system is built if needed; a hidden channel may be enough. On certain routes, a lower area can be paved along the side of the road for water runoff.
Utility routes are checked and must be avoided.
Excavation is done to the required installation depth, coordinated with the drainage system
Excavation continues until compact ground is reached, avoiding soft soil. For pedestrian traffic areas, a 5 cm gravel bed is needed, meaning digging to a depth of 18-23 cm. For vehicle traffic and around pools, an 18-20 cm bed is needed, increasing the digging depth. A wider excavation area is used if curbs will be installed on the sides.
The area is marked out with wooden stakes and string
The area is measured (length, width, depth), using a tape measure or folding ruler.
Gravel (crushed stone or aggregate) is chosen for the load-bearing layer, usually 1.5-2 cm in size. For two load-bearing layers, two different gravel sizes are chosen, with the coarser one at the bottom. Gravel and sand quantities are calculated based on the supplier’s information.
Cobblestone is chosen. For vehicle traffic over 3.5 tons, cobblestone over 8 cm thick is used; for traffic under 3.5 tons, 7 cm cobblestone can also be used. The amount of cobblestone needed is calculated, with some extra added.
The area is bordered with wood battens
The gravel base is laid and compacted (using a plate compactor). A 2-3 cm sand layer (fine sand) is spread over this base. The level is evened out with a straightedge. It’s compacted (tamped). A second, loose sand layer is spread.
Curbs are installed.
Cobblestones are laid on the second sand layer. Stones are set 2 cm higher than the final paving level.
They’re tapped down with a 25 kg hand rammer or a mechanical one, piece by piece, without wetting with water. Unevenness is corrected.
Sand is spread over the whole surface, generously wetted with water, and swept into the joints with a brush until they’re filled.
Depending on the result, a second round of tamping is done.
2. On a semi-dry screed
after building the base (gravel and sand load-bearing layer), the sand is compacted and leveled. The level reached is 7-8 cm lower than the desired final height.
the screed is poured, about 2 cm thick, with the slope needed for water drainage.
before the screed dries, cobblestones are placed and tapped down with a rubber mallet to seat them
the first row of stones is completed using guide strings, and flatness is checked.
the guide string is moved and the second row of stones is installed
flatness is checked along both axes
the gaps between stones are filled with a mix of quartz sand and cement, and the screed is left to set
joints are formed by cutting grooves between the stones, using a round tool (a screwdriver). These grooves let water drain in the direction of the screed’s slope, preventing the screed from cracking due to water pooling in the groove from the expansion and contraction of freeze-thaw cycles.
excess is removed with a brush
foot traffic is avoided until it dries
3. On a reinforced concrete bed
excavation is carried out after calculating the required depth
the reinforced concrete slab is poured, respecting the slopes needed for rainwater drainage
once the concrete has cured, installation continues with adhesive. Paving installation involves: spreading adhesive on the concrete slab, applying adhesive to the cobblestone, tapping the cobblestone into place with a rubber mallet until it reaches the flatness required by the rainwater drainage slope, and grouting the joints with waterproof grout.
