The Ten Books on Architecture
think that one ought not to reject buildings made of brick-work,
provided that they are properly "topped." But I shall explain why this
kind of structure should not be used by the Roman people within the
city, not omitting the reasons and the grounds for them.
17. The laws of the state forbid that walls abutting on public property
should be more than a foot and a half thick. The other walls are built
of the same thickness in order to save space. Now brick walls, unless
two or three bricks thick, cannot support more than one story; certainly
not if they are only a foot and a half in thickness. But with the
present importance of the city and the unlimited numbers of its
population, it is necessary to increase the number of dwelling-places
indefinitely. Consequently, as the ground floors could not admit of so
great a number living in the city, the nature of the case has made it
necessary to find relief by making the buildings high. In these tall
piles reared with piers of stone, walls of burnt brick, and partitions
of rubble work, and provided with floor after floor, the upper stories
can be partitioned off into rooms to very great advantage. The
accommodations within the city walls being thus multiplied as a result
of the many floors high in the air, the Roman people easily find
excellent places in which to live.
18. It has now been explained how limitations of building space
necessarily forbid the employment of brick walls within the city. When
it becomes necessary to use them outside the city, they should be
constructed as follows in order to be perfect and durable. On the top of
the wall lay a structure of burnt brick, about a foot and a half in
height, under the tiles and projecting like a coping. Thus the defects
usual in these walls can be avoided. For when the tiles on the roof are
broken or thrown down by the wind so that rainwater can leak through,
this burnt brick coating will prevent the crude brick from being
damaged, and the cornice-like projection will throw off the drops beyond
the vertical face, and thus the walls, though of crude brick structure,
will be preserved intact.
19. With regard to burnt brick, nobody can tell offhand whether it is of
the best or unfit to use in a wall, because its strength can be tested
only after it has been used on a roof and exposed to bad weather and
time--then, if it is good it is accepted. If not made of good clay or if
not baked sufficiently, it shows itself defective there when exposed to
frosts and rime. Brick that will not stand exposure on roofs can never
be strong enough to carry its load in a wall. Hence the strongest burnt
brick walls are those which are constructed out of old roofing tiles.
20. As for "wattle and daub" I could wish that it had never been
invented. The more it saves in time and gains in space, the greater and
the more general is the disaster that it may cause; for it is made to
catch fire, like torches. It seems better, therefore, to spend on walls
of burnt brick, and be at expense, than to save with "wattle and daub,"
and be in danger. And, in the stucco covering, too, it makes cracks from
the inside by the arrangement of its studs and girts. For these swell
with moisture as they are daubed, and then contract as they dry, and, by
their shrinking, cause the solid stucco to split. But since some are
obliged to use it either to save time or money, or for partitions on an
unsupported span, the proper method of construction is as follows. Give
it a high foundation so that it may nowhere come in contact with the
broken stone-work composing the floor; for if it is sunk in this, it
rots in course of time, then settles and sags forward, and so breaks
through the surface of the stucco covering.
I have now explained to the best of my ability the subject of walls, and
the preparation of the different kinds of material employed, with their
advantages and disadvantages. Next, following the guidance of Nature, I
shall treat of the framework and the kinds of wood used in it, showing
how they may be procured of a sort that will not give way as time goes
on.
CHAPTER IX
TIMBER
1. Timber should be felled between early Autumn and the time when
Favonius begins to blow. For in Spring all trees become pregnant, and
they are all employing their natural vigour in the production of leaves
and of the fruits that return every year. The requirements of that
season render them empty and swollen, and so they are weak and feeble
because of their looseness of texture. This is also the case with women
who have conceived. Their bodies are not considered perfectly healthy
until the child is born; hence, pregnant slaves, when offered for sale,
are not warranted sound, because the fetus as it grows within the body
takes to itself as nourishment all the best qualities of the mother's
food, and so the stronger it becomes as the full time for birth
approaches, the less compact it allows that body to be from which it is
produced. After the birth of the child, what was heretofore taken to
promote the growth of another creature is now set free by the delivery
of the newborn, and the channels being now empty and open, the body will
take it in by lapping up its juices, and thus becomes compact and
returns to the natural strength which it had before.
2. On the same principle, with the ripening of the fruits in Autumn the
leaves begin to wither and the trees, taking up their sap from the earth
through the roots, recover themselves and are restored to their former
solid texture. But the strong air of winter compresses and solidifies
them during the time above mentioned. Consequently, if the timber is
felled on the principle and at the time above mentioned, it will be
felled at the proper season.
3. In felling a tree we should cut into the trunk of it to the very
heart, and then leave it standing so that the sap may drain out drop by
drop throughout the whole of it. In this way the useless liquid which is
within will run out through the sapwood instead of having to die in a
mass of decay, thus spoiling the quality of the timber. Then and not
till then, the tree being drained dry and the sap no longer dripping,
let it be felled and it will be in the highest state of usefulness.
4. That this is so may be seen in the case of fruit trees. When these
are tapped at the base and pruned, each at the proper time, they pour
out from the heart through the tapholes all the superfluous and
corrupting fluid which they contain, and thus the draining process makes
them durable. But when the juices of trees have no means of escape, they
clot and rot in them, making the trees hollow and good for nothing.
Therefore, if the draining process does not exhaust them while they are
still alive, there is no doubt that, if the same principle is followed
in felling them for timber, they will last a long time and be very
useful in buildings.
5. Trees vary and are unlike one another in their qualities. Thus it is
with the oak, elm, poplar, cypress, fir, and the others which are most
suitable to use in buildings. The oak, for instance, has not the
efficacy of the fir, nor the cypress that of the elm. Nor in the case of
other trees, is it natural that they should be alike; but the individual
kinds are effective in building, some in one way, some in another, owing
to the different properties of their elements.
6. To begin with fir: it contains a great deal of air and fire with very
little moisture and the earthy, so that, as its natural properties are
of the lighter class, it is not heavy. Hence, its consistence being
naturally stiff, it does not easily bend under the load, and keeps its
straightness when used in the framework. But it contains so much heat
that it generates and encourages decay, which spoils it; and it also
kindles fire quickly because of the air in its body, which is so open
that it takes in fire and so gives out a great flame.
7. The part which is nearest to the earth before the tree is cut down
takes up moisture through the roots from the immediate neighbourhood and
hence is without knots and is "clear." But the upper part, on account of
the great heat in it, throws up branches into the air through the knots;
and this, when it is cut off about twenty feet from the ground and then
hewn, is called "knotwood" because of its hardness and knottiness. The
lowest part, after the tree is cut down and the sapwood of the same
thrown away, is split up into four pieces and prepared for joiner's
work, and so is called "clearstock."
8. Oak, on the other hand, having enough and to spare of the earthy
among its elements, and containing but little moisture, air, and fire,
lasts for an unlimited period when buried in underground structures. It
follows that when exposed to moisture, as its texture is not loose and
porous, it cannot take in liquid on account of its compactness, but,
withdrawing from the moisture, it resists it and warps, thus making
cracks in the structures in which it is used.
9. The winter oak, being composed of a moderate amount of all the
elements, is very useful in buildings, but when in a moist place, it
takes in water to its centre through its pores, its air and fire being
expelled by the influence of the moisture, and so it rots. The Turkey
oak and the beech, both containing a mixture of moisture, fire, and the
earthy, with a great deal of air, through this loose texture take in
moisture to their centre and soon decay. White and black poplar, as well
as willow, linden, and the agnus castus, containing an abundance of
fire and air, a moderate amount of moisture, and only a small amount of
the earthy, are composed of a mixture which is proportionately rather
light, and so they are of great service from their stiffness. Although
on account of the mixture of the earthy in them they are not hard, yet
their loose texture makes them gleaming white, and they are a convenient
material to use in carving.
10. The alder, which is produced close by river banks, and which seems
to be altogether useless as building material, has really excellent
qualities. It is composed of a very large proportion of air and fire,
not much of the earthy, and only a little moisture. Hence, in swampy
places, alder piles driven close together beneath the foundations of
buildings take in the water which their own consistence lacks and remain
imperishable forever, supporting structures of enormous weight and
keeping them from decay. Thus a material which cannot last even a little
while above ground, endures for a long time when covered with moisture.
11. One can see this at its best in Ravenna; for there all the
buildings, both public and private, have piles of this sort beneath
their foundations. The elm and the ash contain a very great amount of
moisture, a minimum of air and fire, and a moderate mixture of the
earthy in their composition. When put in shape for use in buildings they
are tough and, having no stiffness on account of the weight of moisture
in them, soon bend. But when they become dry with age, or are allowed to
lose their sap and die standing in the open, they get harder, and from
their toughness supply a strong material for dowels to be used in joints
and other articulations.
12. The hornbeam, which has a very small amount of fire and of the
earthy in its composition, but a very great proportion of air and
moisture, is not a wood that breaks easily, and is very convenient to
handle. Hence, the Greeks call it "zygia," because they make of it yokes
for their draught-animals, and their word for yoke is [Greek: zyga].
Cypress and pine are also just as admirable; for although they contain
an abundance of moisture mixed with an equivalent composed of all the
other elements, and so are apt to warp when used in buildings on account