Trullo conical rooves, flat stones, no mortar

This video contrasts modern roofing with ancient Italian construction, exploring how roofs on the italian peninsula, built 600 years ago without mortar or nails, still stand strong. It's a fascinating look at history and home maintenance, demonstrating durable building techniques that challenge contemporary architecture.

I know parts of Italy get strong earthquakes, and looking at that teaser pic I cannot for the life of me see that holding up in a tremor.

I saw a show last night that featured several homes with that kind of roof that have withstood the test of time.

Beautiful!

The video has details of conical structures lasting 600 years.
The image at the start is not clear, but it actually shows a section through the structure.

I don't know enough about building with rocks, but I do know a bit about how Japan built homes out of wood that were designed to "wiggle" rather than collapse during an earthquake.

Is it possible to design with rock in such a way that it will "shift towards stability" rather than away?  When Hubby built a base to park a trailer on, he used a vibrator machine (OK, there's bound to be a technical name for it, but I don't know it) and the theory was that it would compact the gravel to make it more solid. He was doing it nice and neatly going north-south repeatedly. I sent my son up and asked him to do it east-west and then on the diagonals. I had to explain to Hubby my rational... but he seemed to agree with it.

The size of the earthquake is everything. There is plenty of evidence of severe earthquakes collapsing ancient and modern buildings alike. Did these roofs just get lucky, or is there clear evidence of significant earthquakes not damaging them?

Since I don't really have a lot of confidence in this particular Youtube channel as a primary source, I went looking and found this:

https://www.mdpi.com/2075-5309/15/17/3195

Evidently, these buildings do use lime mortar and organic matter in the infill mix. That would make them a lot more resilient when they start to shake.

Phil Stevens wrote:Since I don't really have a lot of confidence in this particular Youtube channel as a primary source, I went looking and found this...

Well done Phil!

I had seen photos of the buildings on travel sites, so I knew that the buildings seemed to exist for real, but that doesn't make the video accurate regarding the claims they make.

The building do not appear to have chimneys, so I wonder how people traditionally cooked, unless they did cooking outside.

I also wonder about the video's claim that the people were miserably cold in the winter. Unless wood was unavailable for heating, I would expect that the stone walls acting as thermal mass would have a very positive effect at keeping the building warm in the winter. Humans have known how to stay warm for thousands of years.  

Jay Angler wrote:
I also wonder about the video's claim that the people were miserably cold in the winter. Unless wood was unavailable for heating, I would expect that the stone walls acting as thermal mass would have a very positive effect at keeping the building warm in the winter. Humans have known how to stay warm for thousands of years.  

The article talks about the thermal break provided by the infill layer, and also suggests that the organic matter incorporated in the rubble helps insulate as well. The verdict seems to be that they're comfortable enough in a Mediterranean climate. I don't think they would work in a place with serious winters.

Phil, I cannot see where the second reference talks about the older buildings having used lime mortar to construct the roof?

Have a look in section 2.1 (Case Study):

The structural scheme is reported in Figure 2. The base structure comprises a 40 cm thick external layer of dressed limestone blocks, a 30 cm thick internal layer of similar stone construction, and a 40 cm thick core of rubble stone with lime mortar infill. The conical roof system utilizes a different configuration with external covering of chiancarelle (thin limestone slabs 3–7 cm thick), structural cannele forming concentric rings of shaped stones, and core filling of mixed stone fragments with organic materials including straw. The construction technique demonstrates remarkable sophistication in managing structural forces through geometry rather than material strength, with the conical form distributing vertical loads efficiently while thick walls provide lateral stability.

Also see passages in section 3 where they discuss the model development, particularly this bit:

The core material properties were estimated based on the heterogeneous composition documented through endoscopic analysis, with reduced stiffness values reflecting the composite nature of rubble stone, lime mortar, and organic materials

And this part of section 4.2:

Void detection within the core material revealed approximately 8% void content distributed non-uniformly throughout the structure. Higher void concentrations occur in the upper cone sections where core material consists primarily of loose stone fragments and organic matter. The base sections show lower void content due to the presence of lime mortar that provides better consolidation of rubble stone core material.

Apparently there's quite a bit of mortar down low, and then as they went higher it turned more to grass, leaves, and twigs mixed in with the rubble.

Thanks Phil, but I still dont see mention of mortar use.