Who did build the domes of the trulli and how?

Peasants were the builders of their own trulli. The knowledge of the constructive rules to adopt was transmitted from generation to generation. This fact implies that the trulli builders were not specialized worker but people occasionally involved in particular moments of their life for building their own home or for giving a contribute in the sister’s home, the cousin’s, the niece’s and so on. Due to this fact the constructive methodologies were very simple and they never evolved toward better technical solutions implying a more organised and systematic work. A clue of this fact is the methodology for building the domes of the trulli. After a first ring of squared stones was placed, a second ring followed simply leaned over the first. Being the stones originally squared on early stage, all the rings leaned on horizontal and parallel plains. The upper ring had just a diameter a bit shorter so that every single squared stone might be supported bending out a bit. A third, a fourth ring and so on was placed to form a roughly shaped dome, using smaller stones as rings grew up. Controlling the diminishing ratio of the diameters was quite simple posing a pole as vertical axis and then using a string. Sometimes a round keystone completed the dome on the top closing the last littlest ring. The inner surface was then shaped chiselling the edges poking out on the lower part of every single stone. This type of structure was self-bearing and no wooden outlining shapes where performed to build the dome.

Normally every stone or brick of a dome gives a contribute to react to forces weighting on it. To optimize its performance, experienced builders cut the stones as wedges and place the single stones leaned on the outlining shape with the right angle. Only after the placement of a last keystone the provisional outlining shape may be removed.

As you can imagine this technique is much more efficient than the peasants’ technique based on some simplifications: stones are all squared on early stage and they are placed without a precise angle. There was no aim of optimizing their adherence over their own weight. No refined woodworking was necessary to perform an outlining shape. The photos show the main dome of Trullo della Luna before and after the restoration. I will be back again about this topic as here my post finishes but I have many other things to explain about the constructive techniques of the trulli!