Roman Roofs Inverted

[Faustus]

Part One

A visual aerial survey^*1) of Pompeii allows us to see an important aspect of the living style of the residents of Pompeii at the moment of the eruption of Vesuvius; something we can

Edited August 5, 2008 by Faustus

[Northern Neil]

Thanks for a very illuminating and (for me) particularly useful post. Maybe this could be expanded into a featured article? I wonder wether or not the water collected would have fed into some sort of town-wide supply, and wether sluices operated to allow excess water to run off into the sewers in the event of a storm or sustained rain.

 

On some of the larger buildings in Pompeii I noticed that the pitch of some roofs faced outwards as well as inwards. I suppose a building with a single, inward sloped roof could only be built to a certain size before the outer wall became too high, so a roof with a 'standard' pitch would be then required (although I notice some roofs are flat).

 

In Britain and the other Northern provinces there was of course no need to exercise such water conservation methods, and things such as compluvia are not found. However, the Romans, being a traditional lot, still appeared to build houses and other structures with inward facing roofs - most principiae in forts are like this, and also many villas and larger houses in towns. Maybe what started as a water conservation measure became a specific style, and the provincials continued to build in this way so their houses echoed the style of those from the mediterranean?

 

Here is an example to illustrate what I mean...

 

 

Although there is an absence of an atrium with confluvium/impluvium, the 'Atrium' - in this case, the cross hall of this small principia - is still in evidence, and the inward facing roof of the collonade has become a style feature rather than the neccesity it started out as. The principia itself is (modelled on) that of a small auxilliary fort in Northern England. Plenty of rain, but the builders see it as important to maintain the mediterranean style.

Edited August 5, 2008 by Northern Neil

[Faustus]

Thanks NN, I have at least two more parts planned, but I may expand a little more than that.

 

The roof sloping into the interior space allowed for a lower breast wall and more sunlight which was one aim and important, I

[Faustus]

Part Two

What can we learn from taking a closer look at how the Romans and their antecedents managed these problems? This then takes us back to Pompeii where so much is preserved or at least has been faithfully restored . On the outside of the Roman domus or villa we see the simplest of roof terminations; simple systems were (and are still) usually the best and require the least attention for maintenance. There we see flat roof tiles (tegulae)^*5), and their joint-lapping half-circle covering tiles (imbrices)^*6) terminated at the lowest edge (eave) with the simplest of end cap closures (antefixae)^*7). These would have kept pests from taking up residence inside the roof itself, and present a more aesthetic view to viewers on the ground.

 

Once the roof section was visible from the inside of the domus, and perhaps after the refinement of the peristylium was added, we see a different motif example; now we have an amalgam of practical and aesthetic combined with status and culture. For instance on Greek temples^*8) like the Parthenon we see an elaboration of carvings at the roof line which we don

[ASCLEPIADES]

Salve, Amici.

Here comes Marcus Vitruvius Pollio, De Architectura, Liber IV, cp. II, sec. I:

... in aedificiis omnibus insuper conlocatur materiatio variis vocabulis nominata. ea autem uti in nominationibus, ita in re varias habet utilitates. trabes enim supra columnas et parastaticas et antas ponuntur, in contignationibus tigna et axes. sub tectis, si maiora spatia sunt, et transtra et capreoli, si commoda, columen et cantherii prominentes ad extremam suggrundationem. supra cantherios templa, deinde insuper sub tegulas asseres ita prominentes uti parietes proiecturis eorum tegantur.

 

"...In all buildings the timber framed work, which has various names, crowns them. The timbers vary as much in their uses as in their names. Those are called bressummers (trabes) which are placed over columns, pilasters (parastat

[Faustus]

[1] I wonder wether or not the water collected would have fed into some sort of town-wide supply, and wether sluices operated to allow excess water to run off into the sewers in the event of a storm or sustained rain.

 

[2] On some of the larger buildings in Pompeii I noticed that the pitch of some roofs faced outwards as well as inwards. I suppose a building with a single, inward sloped roof could only be built to a certain size before the outer wall became too high, so a roof with a 'standard' pitch would be then required (although I notice some roofs are flat).

 

[3] In Britain and the other Northern provinces there was of course no need to exercise such water conservation methods, and things such as compluvia are not found. However, the Romans, being a traditional lot, still appeared to build houses and other structures with inward facing roofs - most principiae in forts are like this, and also many villas and larger houses in towns. Maybe what started as a water conservation measure became a specific style, and the provincials continued to build in this way so their houses echoed the style of those from the mediterranean?

 

[4] Although there is an absence of an atrium with confluvium/impluvium, the 'Atrium' - in this case, the cross hall of this small principia - is still in evidence, and the inward facing roof of the collonade has become a style feature rather than the neccesity it started out as. The principia itself is (modelled on) that of a small auxilliary fort in Northern England. Plenty of rain, but the builders see it as important to maintain the mediterranean style.

 

[1] This would make perfect sense. I have read that little or no excavation has taken place to explore these kinds of possibilities; mostly the excavation has taken place as recent

[Faustus]

(Part three)

Although we seem to see the

[ASCLEPIADES]

Salve, Amici.

Here comes Caius Suetonius Tranquillus Vita Divi Augusti cp. XCII, sec. I:

 

Sed et ostentis praecipue movebatur. Enatam inter iuncturas lapidum ante domum suam palmam in compluvium deorum Penatium transtulit, utque coalesceret magno opere curavit.

 

But he was especially affected by prodigies. When a palm tree sprang up between the crevices of the pavement before his house, he transplanted it to the inner court beside his household gods and took great pains to make it grow.

Edited August 11, 2008 by ASCLEPIADES

[Faustus]

Salve, Amici.

Here comes Caius Suetonius Tranquillus Vita Divi Augusti cp. XCII, sec. I:

 

Sed et ostentis praecipue movebatur. Enatam inter iuncturas lapidum ante domum suam palmam in compluvium deorum Penatium transtulit, utque coalesceret magno opere curavit.

 

But he was especially affected by prodigies. When a palm tree sprang up between the crevices of the pavement before his house, he transplanted it to the inner court beside his household gods and took great pains to make it grow.

 

Thanks for that A.

 

The bolded references of

[Northern Neil]

In a landscaped area such as a horta^*14) the streams would cause erosion or be otherwise objectionable (who needs streams of water being thrown splashing about, except into an impluvium?) and so perhaps oftentimes they were just decorative.

 

Regarding erosion, I am surprised there is no sign of it even in the impluvia. The 'drop' for the captured water was considerable - in some cases 20 feet plus, and in a downpour there must have been some power by the time the water hit the impluvium. Further, the impluvia are often tesselated, which is quite a fragile construct given the power of the water falling into it. Another thought occurs: the impluvia are quite shallow, about 6 - 12 inches. In a strong downpour, the splash and spray in the atrium must have been considerable.

[Faustus]

In a landscaped area such as a horta^*14) the streams would cause erosion or be otherwise objectionable (who needs streams of water being thrown splashing about, except into an impluvium?) and so perhaps oftentimes they were just decorative.

Regarding erosion, I am surprised there is no sign of it even in the impluvia. The 'drop' for the captured water was considerable - in some cases 20 feet plus, and in a downpour there must have been some power by the time the water hit the impluvium. Further, the impluvia are often tesselated, which is quite a fragile construct given the power of the water falling into it. Another thought occurs: the impluvia are quite shallow, about 6 - 12 inches. In a strong downpour, the splash and spray in the atrium must have been considerable.

Well noted NN.

 

I don't think we often give much thought to the "dynamic" quality which would've been created in a rain shower. Also the amount of increase or concentration in a confined area like your roof for instance; the area of your compluvium (and inpluvium below) are but a fraction of the watershed area above. Water had to come down in a torrent in the whole of the caevaedium in a good rain shower. When the 'animal head downspouts' were present there had to be adequate "behind the fascia" storage space. I will give a schematic treatment of that in my next "part".

 

Of course the fact that the surroundings were masonry helped, but there must have been upholstered stuff there as well as wood too. One thing though, the presence of windy conditions to scatter the spray would have been minimized in the surrounding enclosed spaces of the domus.

 

I was aware of the shallow depth of the impluvium, which meant that there was not a whole lot of "demand" storage there. The means of draining it must have been fairly complex and reliable. It would be interesting to see a design or schematic rendering of it. We can think of the consequences in a failure.

Edited August 11, 2008 by Faustus

[ASCLEPIADES]

Thanks for that A.

 

The bolded references of

[Faustus]

(Part four)

When they were used how were the Downspout Heads made and what wre they made of? If they were of Terra Cotta then they must have been

Edited August 16, 2008 by Faustus