Notes and Sketches: Civil, Military, and Naval Architecture (1901) - Page 22

On the Foundations of Buildings

The earth that is most suitable for supporting the weight of a great structure is that which is composed of tufa (tufo) A type of porous rock formed from volcanic ash, common in Italian architecture or of very hard and compact gravel. If one must build upon sandy soil, it is necessary to dig until one finds the solid bed of the earth, or to use piles (pali) Wooden stakes driven into the ground to provide a stable foundation in soft soil made of oak or alder, driven deep and close together.

Water is the enemy of foundations

One must observe with great care the movement of the waters in the vicinity of the building. For if a stream or a hidden vein of water should pass beneath the foundations, it will, over time, carry away the finer parts of the earth, leaving the structure to lean or to crack.

Of the Proportions of the Walls

The thickness of the wall at its base should be determined by the height it must reach and the weight of the roof it must sustain. See the rule of the tenth part Leonardo often referenced the Vitruvian principle that the thickness of a foundation should be greater than the wall above it.

Observations on the Flow of Rivers

When a river strikes the bank, it does not remain there, but rebounds like a ball and strikes the opposite bank with equal force.

Type of Bank	Effect of Water	Necessary Remedy
Sandy	Rapid erosion	Stone reinforcement
Clay	Slow softening	Drainage channels
Rock	Minimal change	None required

original: "l'acqua che percuote la ripa"

The water that falls from a height into a basin will dig a deep hole at the point of its impact, and the earth that is removed from that hole will be deposited further down the stream, forming a sandbank or shoal?. This must be considered when building bridges, lest the central piers (pile) be undermined by the very force of the water they are meant to divide.

The center of the arch must be stronger than its sides