VITRUVIUS, BOOK II, CHAPTER 8
On walling



1. Structurarum genera sunt haec: reticulatum quo nunc omnes utuntur, et antiquum quod incertum dicitur. Ex his venustius est reticulatum, sed ad rimas faciendas ideo paratum, quod in omnes partes dissoluta habet cubilia et coagmenta. Incerta vero caementa alia super alia sedentia inter seque inbricata non speciosam sed firmiorem quam reticulata praestant structuram.

Translation

1. There are two kinds of walling; one like network, opus reticultatum, which all use now, and the old manner which is called opus incertum. Of these the reticulatum is more graceful, but it is likely to cause cracks because it has the beds and joints in every direction. The "uncertain" rough work, opus incertum, lying course above course and breaking joints, furnishes walling which is not pleasing but is tronger than the reticulatum.

2. Utraque autem ex minutissimis sunt instruenda, uti materia ex calce et harena crebriter parietes satiati diutius contineantur. Molli enim et rara potestate cum sint, exsiccant sugendo e materia sucum; cum autem superarit et abundarit copia calcis et harenae, paries plus habens umoris non cito fient evanidus, sed ab his continetur. Simul autem umida potestas e materia per caementorum raritatem fuerit exsucta calxque ab harena discedat et dissolvatur, item caementa non possunt cum his cohaerere, sed in vetustatem parietes efficiunt ruinosos.

Translation

2. Both kinds of walling are to be built with very minute stones; so that the walls, thoroughly saturated with mortar of lime and sand, may hold longer together. For since the stones are of a soft and open nature, they dry up the moisture by sucking it out of the mortar. But when the supply of lime and sand is abundant, the wall having more moisture will not quickly become perishable but holds together. When once, also, the moist power has been sucked out of the mortar, through the loose structure of the rubble, and the lime separates from the sand and is dissolved, the rubble also cannot cohere with them, but renders the walls ruinous with lapse of time.

3. Id autem licet animadvertere etiam de nonnullis monumentis, quae circa urbem facta sunt e marmore seu lapidibus quadratis intrisecusque medio calcata: structuris vetustate evanida facta materia caementorumque exstructa raritate, proruunt et coagamentorum ab ruina dissolutis iuncturis dissipantur.

Translation

3. This we may observe from some tombs which are built near the city, faced with marble or squared stone, and, in the interior, constructed with walling material pressed down. The mortar becomes perishable in time and is drawn out through the loose joints of the rubble. Hence the tombs collapse and disappear when the union of the joints is broken by settlement.

4. Quodsi qui noluerit in id vitium incidere, medio cavo servato secundum orthostatas intrinsecus ex rubro saxo quadrato aut ex testa aut ex silicibus ordinariis struat bipedales parietes, et cum his ansis ferreis et plumbo frontes vinctae sint. Ita enim non acervatim, sed ordine structum opus poterit esse sine vitio sempiternum, quod cubilia et coagmenta eorum inter se sedentia et iuncturis alligata non protrudent opus neque orthostatas inter se religatos labi patiuntur.

Translation

4. But if anyone does not wish to fall into this fault, let him keep the middle hollow behind the facings, and, on the inside, build walls two feet thick of red square stone or of baked brick or of lava, laid in proper courses, and let the facings be tied to these by iron clamps run in with lead. For thus the work is not built all of a heap but in order, and can last; because the beds and joints settling together and bound by ties do not thrust the work forward nor allow the facings bound in this way to give.

5. Itaque non est contemnenda Graecorum structura; utuntur e molli caemento polita, sed cum discesserunt a quadrato, ponunt de silice seu lapide duro ordinaria, et ita uti latericia struentes alligant eorum alternis coriis coagmenta, et sic maxime ad aeternitatem firmas perficiunt virtutes. Haec autem duobus generibus struuntur; ex his unum isodomum, alterum pseudisodomum appellatur.

Translation

5. Therefore the walling of the Greeks is not to be made light of. For the do not employ walling of soft rubble with stucco facing, but when they depart from ashlar, they lay courses of lava or hard stone, and, as with brick buildings, they bind their joints in alternate courses, and so they produce strength firm enough to last. Well these are built in two kinds. Of these one is called isodomum, the other is called pseudoisodomum.

6. Isodomum dicitur, cum omnia coria aequa crassitudine fuerint structa; pseudisodomum cum inpares et inaequales ordines coriorum diriguntur. Ea utraque sunt ideo firma, primum quod ipsa caementa sunt spissa et solida proprietate neque de materia, possunt exsugere liquorem, sed conservant ea in suo umore ad summam vetustatem; ipsaque eorum cubilia primum plana et librata posita non patiuntur ruere materiam, sed perpetua parietum crassitudine religata continent ad summam vetustatem.

Translation

6. It is called isodomum when all the courses are built of an equal thickness; pseudoisodomum when the courses are unequal and unlike. Both are firm, for the reason especially that the rubble itself is of a thick and solid property, and cannot suck out the moisture from the mortar; the rubble preserves the mortar with its moisture for a long time; and the bed-joints of the stone, being laid flat and levelled, do not allow the mortar to sink down; but the stones being bonded in the unbroken thickness of the walls, keep the mortar together for a long time.

7. Altera est quam enplecton appellant, qua etiam nostri rustici utuntur. Quorum frontes poliuntur, reliqua ita, uti sunt nata, cum materia conlocata alternis alligant coagmentis. Sed nostri celeritati studentes, erecta conlocantes frontibus serviunt et in medio faciunt fractis separatim cum materia caementis. Ita tres suscitantur in ea structura crustae, duae frontium et una media farturae. Graeci vero non ita, sed plana conlocantes et longitudines eorum alternis in crassitudinem instruentes, non media farciunt, sed e suis frontatis perpetuam et unam crassitudinem parietum consolidant. Praecaetera interponunt singulos crassitudine perpetua utraque parte frontatos, quos diatonous appellant, qui maxime religando confirmant parietum soliditatem.

Translation

7. The second is that which they call enplecton, which our country people still use. In this the facings are dressed; the rest of the stones are laid with mortar in their natural state, and they bond them with alternate joints. But people nowadays, being eager for speedy building, attend only to the facing, setting the stones on end, and fill it up in the liddle with broken rubble and mortar. Thus three slices are raised in this walling, two of the facings, and a middle one of the filling in. Not so the Greeks who lay the stones level and put the headers and stretchers alternately. Thus they have not to fill in the middle, but with their through facing stones they render solid the unbroken and single thickness of the walls. In addition to the rest, they insert special stones facing on either front of unbroken thickness. These they call diatonos (through-stones), and they, by bonding, especially strengteh the solidity of the wall.

8. Itaque si qui voluerit ex his commentariis animadvertere et elegere genus structurae, perpetuitatis poterit rationem habere. Non enim quae sunt e molli caemento subtili facie venustatis, non eae possunt esse in venustate non ruinosae. Itaque cum arbitrio communium parietum sumuntur, non aestimat eos quanti facti fuerint, sed cum ex tabulis inveniunt eorum locationes, pretia praeteritorum annorum singulorum deducunt octogesimas et ita - ex reliqua summa parte reddi pro his parietibus - sententiam pronuntiant eos non posse plus quam annos LXXX durare.

Translation

8. Therefore if anyone will from these commentaries observe and select a style of walling, he will be able to take account of durability. For those which are of soft rubble with a thin and pleasing facing cannot fall to give way with lapse of time. Therefore when arbitrators are taken for party-walls, they do not value them at the price at which they were made, but when from the accounts they find the tenders for them, they deduct as price of the passing of each year the 80th part, and so - in that from the remaining sum repayment is made for these walls - they pronounce the opinion that the walls cannot last more than 80 years.

9. De lactericiis vero, dummodo ad perpendiculum sint stantes, nihil deducitur, sed quanti fuerint olim facti, tanti esse semper aestimantur. Itaque nonnullis civitatibus et publica opera et privatas domos etiam regias a latere structas licet videre: et primum Athenis murum, qui spectat ad Hymettum montem et Pentelensem; item Patris in aede Iovis et Herculis latericias cellas, cum circa lapideae in aede epistylia sint et columnae; in Italia Arretio vetustum egregie factum murum. Trallibus domus regibus Attalicis facta, quae ad habitandum semper datur ei, qui civitatis gerit sacerdotium. Item Lacedaemone e quibusdam parietibus etiam picturae excisae intersectis lateribus inclusae sunt in ligneis formis et in comitium ad ornatum aedilitatis Varronis et Murenae fuerunt adlatae.

Translation

9. There is no deduction made from the value of brick walls provided that they remain plumb; but they are always valued at as much as they were built for. Therefore in some cities we may see both public works and private houses and even palaces built of brick: and first, the wall at Athens which looks to mount Hymettus and Pentelicus; also at Patrae, brick cellae in the temple of Jupiter and Hercules, while round the temple there are entablatures and columns of stone; in Italy at Arezzo there is an old brick wall excellently built. At Tralles there is a palace built for the Attalid kings, which now is always given for a houose to him who is the Priest of the City: also at Lacedaemon the bricks were cut through from certain walls, the paintings were removed and enclosed in wooden frames, and brought into the Comitium as an ornament for the aedileship of Varro and Murena.

10. Croesi domus, quam Sardiani civibus ad requiescendum aetatis otio seniorum collegio gerusiam dedicaverunt; item Halicarnasso potentissimi regis Mausoli domus, cum Proconnensio marmore omnia haberet ornata, parietes habet latere structos, qui ad hoc tempus egregiam praestant firmitatem ita tectoriis operibus expoliti, uti vitri perluciditatem videantur habere. Neque is rex ab inopia id fecit; in inftnitis enim vectigalibus erat fartus, quod imperabat Cariae toti.

Translation

10. There is the palace of Croesus, which the people of Sardis dedicated to their fellow-citizens for repose in the leisure of their age, as an Almshouse for the College of the Elders. At Halicarnassus also, although the palace of the mighty king Mausolus had all parts finished with Proconnesian marble, it has walls built of brick. And these to this day maintain a striking firmness, being so finished with plaster work that they seem to have the translucency of glass. Nor was it for lack of means that the king did this. For he was enriched by enormous revenues because he ruled over all Caria.

11. Acumen autem eius et sollertiam ad aedificia paranda sic licet considerare. Cum esset enim natus Mylasis et animadvertisset Halicarnasso locum naturaliter esse munitum, emporiumque idoneum portum utile, ibi sibi domum constituit. Is autem locus est theatri curvaturae similis. Itaque in imo secundum portum forum est constitutum; per mediam autem altitudinis curvaturam praecinctionemque platea ampla latitudine facta, in qua media Mausoleum ita egregiis operibus est factum, ut in septem spectaculis nominetur. In summa arce media Martis fanum habens statuam colossicam acrolithon nobili manu Leocharis factam. Hanc autem statuam alii Leocharis, alii Timothei putant esse. In cornu autem summo dextro Veneris et Mercuri fanum ad ipsum Salmacidis fontem.

Translation

11. We may thus consider his shrewdness and skill in providing buildings. For although he was born at Melisso, he observed at Halicarnassus a place naturally fortified, a suitable market, and a useful harbour, and he there established his palaca. Now that place is like the curvature of a theatre. The forum is placed at the lowest level along the harbour. But about the middle of the natural amphitheatre and, as it were, in a cross gangway, a street is constructed of ample width, in the middle of which the Mausoleum is built of such splendid workmanship that it is named among the Seven Sights of the World. In the middle of the top of the citadel is a temple of Mars having a statue of a colossus with marble extremities made by the famous hand of Leochares, others by Timotheus. On the right wing at the top is a temple of Venus and Mercury against Salmacis' fountain itself.

12. Is autem falsa opinione putatur venerio morbo inplicare eos, qui ex eo biberint. Sed haec opinio quare per orbem terrae falso rumore sit pervagata, non pigebit exponere. Non enim quod dicitur molles et inpudicos ex ea aqua fieri, id potest esse, sed est eius fontis potestas perlucida saporque egregius. Cum autem Melas et Areuanias ab Argis et Troezene coloniam communem eo loci deduxerunt, barbaros Caras et Lelegas eiecerunt. Hi autem ad montes fugati inter se congregantes discurrebant et ibi latrocinia facientes crudeliter eos vastabant. Postea de colonis unus ad eum fontem propter bonitatem aquae quaestus causa tabernam omnibus copiis instruxit eamque exercendo eos barbaros allectabat. Ita singillatim decurrentes et ad coetus convenientes e duro ferroque more commutati in Graecorum consuetudinem et suavitatim sua voluntate reducebantur. Ergo ea aqua non inpudico morbi vitio, sed humanitatis dulcedine mollitis animis barbarorum eam famam est adepta.

Translation

12. This fountain, however, by a mistaken opinion, is thought to afflict with an aphrodisiac disease those who drink from it. And why this opinion has wandered over the world through mistaken rumour it will not be inconvenient to set forth. For this cannot be because, as it is said, people are made effeminate and shameless by that water; the virtue of the spring is clearness and its flavour is excellent. Now when Melas and Arevanias led thither a joint colony from Argos and Troezen, they cast out the barbarians, Carians and Leleges. But these being driven to the hills, gathered together and made raids, and by brigandage they devastated the Greeks cruelly. But afterwards one of the colonists, for the sake of profit, fitted up an inn with complete supplies, near the spring, on account of the goodness of the water, and running the inn, he began to attract the barbarians. So coming down one by one, and mixing with society, they changed of their own accord from their rough and wild habits to Greek customs and affability. Therefore this water obtained such a reputation, not by the plague of an immodest disease, but through the softening of savage breasts by the delights of civilisation.

13. Relinquitur nunc, quoniam ad explicationem moenium eorum sum invectus, totam uti sunt definiam. Quemadmodum enim in dextra parte fanum est Veneris et fons supra scriptus, ita in sinistro cornu regia domus, quam rex Mausolus ad suam rationem conlocavit. Conspicitur enim ex ea ad dextram partem forum et portus moeniumque tota finitio, sub sinistram secretus sub montibus latens portus, ita ut nemo posset, quid in eo geratur, aspicere nec scire, ut rex ipse de sua domo remigibus et militibus sine ullo sciente quae opus essent, spectaret.

Translation

13. Since now I am brought to the description of these walls, it remains to outline it completely as they are. For just as on the right side there are the temple of Venus and the spring above described, so on the left wing is the royal palace which King Mausolos had built to his own plan. From it there is seen on the right side the forum and harbour and the whole circuit of the walls; under the left there is a secret harbour lying hid under high ground, in such a way that no one can see or know what is going on in it, so that the king from his own palace could see what is necessary for his sailors and soldiers, without anyone else knowing.

14. Itaque post mortem Mausoli Artemisiam uxorem eius regnantem Rhodii indignantes mulierem imperare civitatibus Cariae totius, armata classe profecti sunt, uti id regnum occuparent. Tum Artemisiae cum esset id renuntiatum, in eo portu abstrusam classem celatis remigibus et epibatis conparatis, reliquos autem cives in muro esse iussit. Cum autem Rhodii ornata classe in portum maiorem exposuissent, plausum iussit ab muro his darent pollicerique se oppidum tradituros. Qui cum penetravissent intra murum relictis navibus inanibus, Artemisia repente fossa facta in pelagum eduxit classem ex portu minore et ita invecta est in maiorem. Expositis autem militibus classem Rhodiorum inanem abduxit in altum. Ita Rhodii non habentes, quo se reciperent, in medio conclusi in ipso foro sunt trucidati.

Translation

14. Therefore when, after the death of Mausolos, his wife Artemisia began to reign, the Rhodians were indignant that a woman should rule over the cities throughout Caria, and equipped a fleet they set out to seize the kingdom. It was reported to Artemisia. She hid the fleet in the harbour, concealing the rowers and the marines she had got together, and ordered the rest of the citizens to man the walls. Now when the Rhodians had landed, with a fleet well equipped, in the greater harbour, she commanded the citizens to greet them from the walls and to promise to surrender the town. These left their ships unmanned and penetrated within the wall. Artemisia, using an artificial outlet into the sea, suddenly led out her fleet from the lesser harbour and thus sailed into the greater. She then landed her soldiers and took the empty Rhodian fleet away to sea. So the Rhodians, having no place of retreat, were surrounded and killed in the forum itself.

15. Ita Artemisia in navibus Rhodiorum suis militibus et remigibus inpositis Rhodum est profecta. Rhodii autem, cum prospexissent suas naves laureatas venire, opinantes cives victores reverti hostes receperunt. Tum Artemisia Rhodo capta principibus occisis tropaeum in urbem Rhodo suae victoriae constituit aeneasque duas statuas fecit, unam Rhodiorum civitatis, alteram suae imaginis, et ita figuravit Rhodiorum civitati stigmata inponentem. Id autem postea Rhodii religione inpediti, quod nefas est tropaea dedicata removeri, circa eum locum aedificium struxerunt et id erecta Graia statione texerunt, ne qui possit aspicere, et id abaton vocitari iusserunt.

Translation

15. So Artemisia, placing her own troops and rowers in the ships of the Rhodians sailed for Rhodes. But when the Rhodians saw their own ships wreathed with laurel, they thought their fellow citizen returned victorious and let the enemy in. The Artemisia took Rhodes, killed the leading citizens, and set up a trophy of her victory in the city of Rhodes, the other in her own likeness. She had the latter figured as settinga brand upon the city of Rhodes. But afterwards the Rhodians, being restrained by a religious scruple because it is forbidden for trphies once dedicated to be removed, erected a building round the spot and protected it with a Greek outpost to prevent anyone seeing, and ordered this to be called 'unapproachable'.

16. Cum ergo tam magna potentia reges non contempserint latericiorum parietum structuras, quibus et vectigalibus et praeda saepius licitum fuerat non modo caementicio aut quadrato saxo sed etiam marmoreo habere, non puto oportere inprobare quae sunt e latericia structura facta aedificia, dummodo recte sint tecta. Sed id genus quid ita populo Romano in urbe fieri non oporteat, exponam, quaeque sunt eius rei causae et rationes, non praetermittam.

Translation

16. Since, therefore, kings of very great power have not disdained walls built of brick (in cases where wealth gained by taxation and plunder allowed the use not only of rubble or squared stone, but even of marble), I do not think that buildings which are made of brick walls are to be disregarded so long as they are duly roofed. But why this fashion ought not to be followed out by the Roman people in the city I will set forth, and will not omit the causes and reasons of this.

17. Leges publicae non patiuntur maiores crassitudines quam sesquipedales constitui loco communi; ceteri autem parietes, ne spatia angustiora fierent, aedem crassitudine conlocantur. Latericii vero, nisi diplinthii aut triplinthii fuerint, sesquipedali crassitudine non possunt plus unam sustinere contignationem. In ea autem maiestate urbis et civium infinita frequentia innumerabiles habitationes opus est explicare. Ergo cum recipere non possit area planata tantam multitudinem ad habitandum in urbe, ad auxilium altitudinis aedificiorum res ipsa coegit devenire. Itaque pilis lapideis structuris testaceis, parietibus caementiciis altitudines extructae contignationibus crebris coaxatae cenaculorum ad summas utilitates perficiunt despectationes. Ergo moenibus e contignationibus variis alto spatio multiplicatis populus Romanus egregias habet sine inpeditione habitationes.

Translation

17. Public statutes do not allow a thickness of more than a foot and a half to be used for party walls. But other walls also are put up of the same thickness lest the space be too much narrowed. Now brick walls of a foot and a half - not being two or three bricks thick - cannot sustain more than one story. Yet with the greatness of the city and the unlimited crowding of citizens, it is necessary to provide very numerous dwellings. Therefore since a level site could not receive such a multitude to dwell in the city, circumstances themselves have compelled the resort to raising the height of buildings. And so by means of stone pillars, walls of burnt brick, party walls of rubble, towers have been raised, and these being joined together by frequent board floors produce upper stories with fine views over the city to the utmost advantage. Therefore walls are raised to a great height through various stories, and the Roman people has excellent dwellings without hindrance.

18. Quoniam ergo explicata ratio est, quid ita in urbe propter necessitatem angustiarum non patiuntur esse latericios parietes, cum extra urbem opus erit his uti, sine vitiis ad vetustatem, sic erit faciendum. Summis parietibus structura testacea sub tegula subiciatur altitudine circiter sesquipedali habeatque proiecturas coronarum. Ita vitari poterunt quae solent in his fieri vitia; cum enim in tecto tegulae fuerint fractae aut a ventis deiectae, qua possint ex imbribus aqua perpluere, non patietur lorica testacea laedi laterem, sed proiectura coronarum reiciet extra perpendiculum stillas et ea ratione servaverit integras parietum latericiorum structuras.

Translation

18. Now, therefore, the reason is explained why, because of the limited space in the city, they do not allow walls to be of sun-dried bricks. When it shall be necessary to use them, outside the city, such walls will be sound and durable after the following manner. At the top of the walls let walling of burnt brick be put beneath the tiles, and let it have a projecting cornice. So the faults which usually happen here can be avoided. For when tiles in the roof are broken or thrown down by the wind (where rain-water could pass through from showers), the burnt brick shield will not allow to brickwork to be damaged; but the projection of the cornices will throw the drippings outside the facing line, and in that way will keep intact the structure of brick walls.

19. De ipsa autem testa, si sit optima seu vitiosa ad structuram, statim nemo potest iudicare, quod in tempestatibus et aestate in tecto cum est conlocata, tunc, si est firma, probatur; namque quae non fuerit ex creta bona aut parum erit cocta, ibi se ostendit esse vitiosam gelicidiis et pruina tacta. Ergo quae non in tectis poterit pati laborem, ea non potest in structura oneri ferendo esse firma. Quare maxime ex veteribus tegulis tecta structa; parietes firmitatem poterunt habere.

Translation

19. But whether the baked brick itself is very good or faulty for building, no one can judge its strength off hand, because only when it is laid as a coping is it tested by weathering and lapse of time. For brickwork that is not made of good clay or is too little baked shows its faults on the work when wheatered by ice or hoar-frost. Therefore the brickwork which cannot stand the strain in the coping courses cannot be strong enough in the walling to carry loads. Wherefore the coping courses are specially built from old tiles, and the walls will be strong enough.

20. Craticii vero velim quidem ne inventi essent; quantum enim celeritate et loci laxamento prosunt, tanto maiori et communi sunt calamitati, quod ad incendia uti faces sunt parati. Itaque satius esse videtur inpensa testaceorum in sumptu, quam compendio craticiorum esse in periculo. Etiamque in tectoriis operibus rimas in his faciunt arrectariorum et transversariorum dispositione, Cum enim linuntur, recipientes umorem turgescunt, deinde siccescendo contrahuntur et ita extenuati disrumpunt tectoriorum soliditatem. Sed quoniam nonnullos celeritas aut inopia aut in pendenti loco dissaeptio cogit, sic erit faciundum. Solum substruatur, ut sit intactum ab rudere et pavimento; obruta enim in his cum sunt, vetustate marcida fiunt; deinde subsidentia proclinantur et disrumpunt speciem tectoriorum.
De parietibus et apparitione generatim materiae eorum, quibus sint virtutibus et vitiis, quemadmodum potui, exposui; de contignationibus autem et copiis earum, quibus conparentur, et ad vetustatem non sint infirmae, uti natura rerum monstrat, explicabo.

Translation

20. I could wish that walls of wattlework had not been invented. For however advantageous they are in speed of erection and for increase of space, to that extent are they a public misfortune, because they are like torches ready for kindling. Therefore it seems better to be at greater expense by the cost of burnt brick than to be in danger by the convenience of wattlework walls: for these also make cracks in the plaster covering owing to the arrangement of the uprights and cross-pieces. For when the plaster is applied, they take up the moisture and swell, then when they dry they contract, and so they are rendered thin, and break the solidity of the plaster. But since haste, or lack of means, or partitions made over an open space, somtimes require this construction, we must proceed as follows. Let the foundations be lais high up, so that it is untouched by the rough stones of the pavement; for when they are fixed in these, they become rotten in time; then they settle, and falling forward they break through the surface of the plaster.
With respect to walls and the use of material after its kinds, I have explained their excellences and faults as I have been able. Now with respect to floors and the material from which they are provided, so that they may not be weakened by lapse of time, I will explain as nature shows.

COMMENT

The general structure of this chapter once again shows the purposes of Vitruvius when he wrote his 'De Architectura'. It starts (sentences 1 - 9a) with an explanation of the different kinds of walling that were used in Roman architecture, their advantages and disadvantages, and a comparison to Greek building practices.
In sentence 9b he gives a lot of examples of cities where these building techniques were used in city walls. This enumeration of examples is interwoven with a few anecdotical remarks. And then he comes to Halicarnassos (sentences 10 - 15). This is the occasion to write a great digression about the layout of this city and of the history of a conflict with the Rhodians in which Artemisia, the wife of king Mausolos, played a prominent role. But before he comes to this history we hear about a certain fountain (sentence 12), the water of which should provoke veneral diseases. One can wonder what all this has to do with building technique and if the knowledge of these histories is advantageous to the architect and builder who has to construct a wall.
Te answer is simple: the 'De Architectura' was not meant for a public of experts but in the first place for a general public to which Vitruvius wanted to justify architecture as an art. It is obvious that such a book must contain the quintessens of architecture, but, on the other hand, to keep the attention of the reader and to make appeal on his curiosity it was also necessary to insert a number of anecdotes, mythological and historical digressions.
That this digression stands completely apart from his explanation about walling is proven by the ease with which in sentence 16 he comes back to his main discourse: he needs only three lines to come back to the walling techniques to which the rest of the chapter (sentences 16 - 20) is dedicated.

When we make abstraction from this digression we can see how this chapter falls apart in two sections. The first is about the kinds of Roman walling as compared to Greek walling (sentences 1 - 8), the second is about the properties of unbaked bricks in walls (sentences 16 - 19) with a little note on wattlework.

Vitruvius mades a distinction between opus incertum and opus reticulatum. Both kinds of walling were facings of a concrete or rubble core. Opus incertum consists of irregular blocks and gives a rather disorderly impression while opus reticulatum is made of regular square stones. Opus incertum appears in Roman architecture from the beginning of the 2nd century B.C. but it is quickly superseded by the more beautiful and more regular opus reticulatum.

Opus incertum

Opus reticulatum

Vitruvius compares this method to the Greek building technique which consist mainly of the superposition of horizontal layers of squared natural stones. According to the thickness of these layers he discerns opus isodomum in which all the layers are of a even thickness and opus pseudoisodomum in which the thickness of the layers can differ considerably. In contrast to Roman building practice the concept of this construction was a massive wall which was completely built up of stones. The concrete filling was unknown to the Greeks.

Opus isodomum

Opus pseudoisidomum

A third technique, which can roughly be compared to the Roman building practice, is the so called opus emplecton. This type of walling consists of two external facings composed of stones only worked on the visible site. The interior of the wall is filled with rubble. This type is known in Greek architecture from the end of the 7th century B.C.

In the illustrations below I give examples of a section of a wall in opus isodomum and pseudoisodomum as compared to opus emplecton.

Section of a wall
a) opus isodomum
b) opus pseudoisodomum

Section of a wall
in opus emplecton

The second section (sentences 16 - 20) is about the properties of walls in sun-dried bricks. It is obvious that water and rain as cause of erosion is the greatest enemy of this material. That's why Vitruvius gives the advice to cover sun-dried walls with a few layers of baked bricks and to construct a roof with a great outward projection. On the other hand Sun-dried bricks are not strong enough to support the great loads of a multi-storied building. Because of the lack of space Roman law forbade partition walls of more than 1,5 foot thick. On the other hand, also because of the lack of space, it was necessary to build dwellings with multiple stories. A wall with a thickness of 1 foot (or the length of 1 brick) could only support a roof. When one wished to add a second story it was necessary to construct a wall of 2 feet (or the length of 2 bricks), for a third story the thickness of an additional brick was needed, etc. But speculators wishing to get the highest possible profit, constructed always higher buildings with always thinner partition walls. This practice increased the danger of collapse of these buildings, and, indeed, collapses were a recurrent problem in antique Rome. In order to counter this phenomemen laws were voted from the middle of the 2nd century B.C. to limit the height of buildings. Infractions on this legislation were legion. Finally Augustus issued his Lex Iulia de modo aedificiorum urbis in which the height of a building, as seen from the street, was limited to 70 feet (20,65 metres) (the law said nothing about the parts of the building that were not adjacent to the public way). This law applied to all new buildings. Already existant buildings must be reduced to 70 feet. From this it may be clear that in late republican and early imperial Rome many tenement houses were higher and that passers by were endangered by a possible collapse of one of these constructions.

BIBLIOGRAPHY

Les dix livres d'architecture de Vitruve, Corrigés et traduits en 1684 par C. Perrault, Paris, 1684.
Vitruvius, De Architectura libri X, ed. F. Granger, London, 1962.
Ton Peters, Vitruvius, Handboek bouwkunde, Amsterdam, 1999.
L.Homo, Rome impériale et l'urbanisme dans antiquité, Paris, 1951.
R.Martin, Manuel d'Architecture Grecque, I, Matériaux et techniques, Paris, 1965.
A.Boëthius-J.B.Ward-Perkins, Etruscan and Roman Architecture, Harmondsworth, 1970.
A.McKay, Vitruvius, Architect and Engineer, London, 1978.
K.Sallmann, Bildungsvorgaben des Fachschriftstellers, Bemerkungen zur Pädagogik Vitruvs, in Vitruv-Kolloquium, Darmstadt, 1984.




Illustrations of the Cesariano Edition




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