On Architecture

3. We must also manage to discharge the load of the walls by means of archings composed of voussoirs with joints radiating to the centre. For when arches with voussoirs are sprung from the ends of beams, or from the bearings of lintels, in the first place they will discharge the load and the wood will not sag; secondly, if in course of time the wood becomes at all defective, it can easily be replaced without the construction of shoring.

4. Likewise in houses where piers are used in the construction, when there are arches composed of voussoirs with joints radiating to the centre, the outermost piers at these points must be made broader than the others, so that they may have the strength to resist when the wedges, under the pressure of the load of the walls, begin to press along their joints towards the centre, and thus to thrust out the abutments. Hence, if the piers at the ends are of large dimensions, they will hold the voussoirs together, and make such works durable.

5. Having taken heed in these matters to see that proper attention is paid to them, we must also be equally careful that all walls are perfectly vertical, and that they do not lean forward anywhere. Particular pains, too, must be taken with substructures, for here an endless amount of harm is usually done by the earth used as filling. This cannot always remain of the same weight that it usually has in summer, but in winter time it increases in weight and bulk by taking up a great deal of rain water, and then it bursts its enclosing walls and thrusts them out.

6. The following means must be taken to provide against such a defect. First, let the walls be given a thickness proportionate to the amount of filling; secondly, build counterforts or buttresses at the same time as the wall, on the outer side, at distances from each other equivalent to what is to be the height of the substructure and with the thickness of the substructure. At the bottom let them run out to a distance corresponding to the thickness that has been determined for the substructure, and then gradually

7. Furthermore, inside, to meet the mass of earth, there should be saw-shaped constructions attached to the wall, the single teeth extending from the wall for a distance equivalent to what is to be the height of the substructure, and the teeth being constructed with the same thickness as the wall. Then at the outermost angles take a distance inwards, from the inside of the angle, equal to the height of the substructure, and mark it off on each side; from these marks build up a diagonal structure and from the middle of it a second, joined on to the angle of the wall. With this arrangement, the teeth and diagonal structures will not allow the filling to thrust with all its force against the wall, but will check and distribute the pressure.

8. I have now shown how buildings can be constructed without defects, and the way to take precautions against the occurrence

9. As for the kind of material to be used, this does not depend upon the architect, for the reason that all kinds of materials are not found in all places alike, as has been shown in the first book. Besides, it depends on the owner whether he desires to build in brick, or rubble work, or dimension stone. Consequently the question of approving any work may be considered under three heads: that is, delicacy of workmanship, sumptuousness, and design. When it appears that a work has been carried out sumptuously, the owner will be the person to be praised for the great outlay which he has authorized; when delicately, the master workman will be approved for his execution; but when proportions and symmetry lend it an imposing effect, then the glory of it will belong to the architect.