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Week 31 – The Romans’ Winter Coats Finally Come Off, and Efficiency in Ancient Roman Construction

April 12, 2010

 

Overlooking the center of Rome from beneath a rustic wood pergola in the Villa Sciara Parc, located on the Gianicolo.

 I thought spring arrived in Rome several weeks ago, when the weather warmed and the flowers started to bloom. But clearly, I see things through the eyes of a Bostonian, not a Roman. For the past few weeks, it’s mostly been warm and sunny, with flowers in bloom, and afternoon highs in the low to mid 60’s Fahrenheit, yet Romans have largely persisted in wearing their winter scarves and coats. Last autumn, on an unseasonably hot day, my wife saw a woman faint on the #44 bus. The woman was wearing a wearing a winter parka, zipped all the way up. The bus stopped, there was a lot of commotion, and several people attended to the woman to revive her, but no one thought to even unzip her parka, let alone remove it! After recovering, the woman still didn’t unzip her parka.

From casual observation, it appears that most Romans break-out their winter coat and scarf on a certain day in the early fall, and don’t stop wearing them until a certain day in the spring, regardless of the temperatures. It must be some sort of unwritten rule, like our American convention about “no white pants or shoes before Memorial Day, or after Labor Day”.

The day before Easter in the cortile of Chiesa di San Clemente

The day before Easter, it was warm and sunny, about 65 degrees, not a cloud in the sky – I was out in a local park without a jacket, and many locals were still in their winter jackets, zipped all the way up, with a scarf. The Tuesday after Easter weekend, with the exact same weather, I suddenly saw many locals wearing light spring jackets. Thus, I suspect that the unwritten rule or local tradition in Rome might be that after Pasquetta (“Little Easter”, the day after Easter); one puts away the winter coat and breaks-out the spring jacket.

Another sign that spring has truly arrived in Rome occurred last Friday; the strawberries began to arrive at the American Academy. With the Rome Sustainable Food Project, the food served in the dining hall here is made only from fresh, local, organic, sustainable foods from local farmers. All of our food is from Italy, and 80% is from Lazio, the region of which Rome is a part. Throughout the year, we’ve been able to chart the seasons through the produce which is most abundant in our meals – peppers, pears, apples in the fall; fennel, root vegetables and Clementine in the winter; and now, with the arrival of spring, asparagus, peas and strawberries are very abundant at the meals in the dining hall.

The capitol at the ancient Roman port of Ostia Antica, on a beautiful spring day.

If you were going to build as many buildings and structures as the ancient Romans built, all across a very vast empire, well then you certainly would have needed to be extremely efficient about manner in which you built. And the Romans were.  As often as I look at ancient Roman construction, I find myself continuously impressed with the efficiency of their construction.

Typical top chord connection in Roman style timber truss

Top chord to bottom chord connection in Roman style timber truss.

Stop for girts on sloped top chord of Roman style truss

In my week 21 blog, I described the simplicity, strength and efficiency of Roman connections in timber framing and trusses. The simplicity of these cuts and connections made them much simpler and faster to construct than the more complicated connections in structural timber framing we’ve traditionally used in the Anglo-American connection. With the connections they used, they were also far less inclined to weaken a member by cutting into it.

Roman style timber roof framing at San Giovanni dei Fiorentini, Rome

The Romans did not lack sophistication in their ability to make wood connections – they used complicated 3-dimensional joinery in their furniture, where the demands for a highly finished surface were greater, and the structural loadings were orders of magnitude lower. In the Romans trusses and other structural connections in heavy timber, however, it was all about speed, efficiency, and strength.

The Romans typically did not use temporary wooden formwork to construct their concrete walls.   This added efficiency by saving the time and effort and materials involved  in constructing the wooden formwork, and then stripping it away after the concrete cures (hardens).

Where the Romans DID use temporary wooden formwork or centering (i.e. curved formwork for an arch or vault) was where they really needed it. That tended to be on arches, their two dimensional equivalent (vaults), and their three-dimensional equivalents, domes. (N.B. – It wasn’t until Brunelleschi’s dome on the Duomo (Cathedral) in Florence that someone figures out how to build a large dome or arch without centering.) Even where the Romans used centering, they gained efficiency by:

• tending to minimize the number different sizes of arches on the same buildings , so they could reuse the centering  as often as possible

• using simple wedges to release the centering after the concrete sets, so the centering can be released and removed more easily

• allowing the supports for the wood centering to remain as a permanent part of the building or structure (and often, the impost supports for the centering, which are practical to the construction process, become aesthetically articulations as well)

Brick impost/capital at the springline of the arch supported the temporary wood centering during construction (Ostia Antica)

Travertine imposts at the springline of a failed arch at Ostia Antica supported the temporary wood centering during construction of the brick arch.

Last week I mentioned that the stone or brick facing on Roman concrete walls was not only the facing, but also part of the load-bearing structure, and also the permanent formwork for the walls (in other words, it held the concrete core in place while it cured or “hardened”).   This was a highly efficient form of construction, in that it omitted the need, time, and cost to build wooden formwork just to temporary support the walls during construction, (only to remove it after the concrete cures, the way we typically built concrete walls today).   Furthermore, if we construct stone faced walls today, we’d typically have a mason lay the brick or stone facing on the two outer shells, with mortar, and then after that is done and cured, they fill the core with concrete. 

Brick-faced Roman concrete wall at the Markets of Trajan, Rome

Architect Kiel Moe and I have been looking at many of these ancient Roman concrete walls, and from what we can tell from up-close examination, the triangular brick or wedge-shaped stone facings were NOT laid up in advance of the core –  rather, they were driven-into the very stiff concrete mix, concurrent with the construction of the core of the wall.  This technique of driving the facing into the core concurrently would only be possible with a very stiff concrete mix, like the Romans used – it wouldn’t be possible with the more watery concrete mixes we typically use today. Furthermore, driving the facings into a very stiff concrete mix would be far more efficient with wedge-shaped or triangular masonry facings, which the Romans clearly used.   In terms of physical evidence, if the brick or stone faces were laid-up in advance, there should be a “cold joint” between the concrete core of the wall and the concrete/mortar bonding the face brick or stones, but neither of us has seen a cold joint yet after looking at broken or open sections of many of these ancient walls.   

All these things lead Kiel and me to conclude that the facings were driven into the very stiff concrete mix of the core of the wall, concurrent with the construction of the concrete core.   All these techniques for the stone or brick facing/formwork must have saved time, and added efficiency (not to mention durability) to the wall construction.

Today, efficiency and speed of construction is sometimes thought of as being contrary to quality and durability of construction. The manner in which the ancient Romans built, however, shows us quite clearly that these virtues need not be mutually exclusive.

From the early 20th century to today, we’ve often tended to think of efficiency as deriving from specialization. Whether it’s Henry Ford’s much acclaimed and widely influential use of the assembly line for Model T’s, or today’s incredibly specialized NFL football teams, where each position player has very particular skills and physical attributes (size or speed) suited to a particular task, we often tend to focus on a model of efficiency whereby specialization of the many individual parts is key to the efficiency of the (relatively complex) whole.

That, however, is only one model of efficiency…  The ancient Roman examples of the multiple roles played by single elements – e.g., brick or stone wall facings (weathering facings, load-bearing structure, and permanent formwork) and the imposts of arches (supporting temporary centering, supporting permanent arches, and aesthetic articulation) demonstrates another model of efficiency – one of versatility, where fewer single elements each playing multiple roles that contribute to the efficiency of the (relatively simple) whole.

Brick-faced concrete structure at Ostia Antica

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3 Comments leave one →
  1. April 16, 2010 5:29 pm

    Thank you for your tutorials on Roman construction ! I find new things with each post. How fortunate you are to be able to study in Rome !
    Ed

  2. Shawn permalink
    July 9, 2010 4:52 pm

    I’ve just come across your blog, and your project is fascinating. I suppose you’re familiar with the work of Janet DeLaine and Lynne Lancaster? If not, check them out!
    Best,
    Shawn

    • mbronski permalink*
      October 1, 2010 6:40 pm

      Shawn-

      I don’t know Janet DeLaine’s work, but I will look into it. Thanks for the tip. I do know Lynne Lancaster’s work well, and in fact, I think her book “Concrete Vaulted Constructionin Imperial Rome; Innovations in Context” is absolutely fantastic. It should really be a “must read” for anyone interested in the topic. I had the pleasure of meeting Lynn last fall at the American Academy, and she is very kind and gracious, generous in sharing her knowledge and passion.

      -Matthew

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