ADDING THE FOUNDATIONS
Place the foundations/sub-foundations at a depth of at least 25 cm. Work in layers of 20 cm at the most, and compact with a vibrating plate.
The foundations may consist of: lava, limestone rubble, porphyry rubble, or crushed concrete rubble (grain size: 16-32 mm or 20-40 mm), the voids (about 80%) are filled with topsoil. We advise against brick rubble, as it pulverises over time.