[Footnote: A recent lecture delivered at Carpenters' Hall, London Wall,
E.C.--_Building News_.]
By Professor T. ROGER SMITH, F.R.I.B.A.
Timber, stone, earth, are the three materials most used by the builder
in all parts of the world. Where timber is very plentiful, as in Norway
or Switzerland, it is freely used, even though other materials are
obtainable, and seems to be preferred, notwithstanding the risk of fire
which attends its use. Where timber is scarce, and stone can be had,
houses are built of stone. Where there is no timber and no stone, they
are built of earth--sometimes in its natural state, sometimes made into
bricks and sun-dried, but more often made into bricks and burned.
London is one of the places that occupies a spot which has long ceased
to yield timber, and yields no stone, so we fall back on earth--burnt
into the form of bricks. Brick was employed in remote antiquity. The
Egyptians, who were great and skillful builders, used it sometimes; and
as we know from the book of Exodus, they employed the forced labor of
the captives or tributaries whom they had in their power in the hard
task of brick making; and some of their brick-built granaries and stores
have been recently discovered near the site of the battle of
Tel-el-Kebir.
The Assyrians and Babylonians made almost exclusive use of brickwork in
erecting the vast piles of buildings the shapeless ruins of which mark
the site of ancient Nineveh and of the cities of the valley of the
Euphrates. Their bricks, it is believed, were entirely sun-dried, not
burnt to fuse or vitrify them as ours are, and they have consequently
crumbled into mere mounds. The Assyrians also used fine clay tablets,
baked in the fire--in fact, a kind of terra cotta--for the purpose of
records, covering these tablets with beautifully executed inscriptions,
made with a pointed instrument while the clay was soft, and rendered
permanent by burning. We don't know much about Greek brickwork; but it
is probable that very little brick, if any, was made or used in any part
of Greece, as stone, marble, and timber abound there; but the Romans
made bricks everywhere, and used them constantly. They were fond of
mixing two or more materials together, as for example building walls in
concrete and inserting brickwork at intervals in horizontal layers to
act as courses of bond. They also erected buildings of which the walls
were wholly of brick. They turned arches of wide span in brickwork; and
they frequently laid in their walls at regular distances apart courses
of brick on edge and courses of sloping bricks, to which antiquaries
have given the name of herring-bone work.
The Roman bricks are interesting as records, for it was customary to
employ the soldiers on brick making, and to stamp the bricks with names
and dates; and thus the Roman bricks found in this country give us some
information as to the military commanders and legions occupying
different parts of England at different periods. Flue bricks, for the
passage of smoke under floors and in other situations, are sometimes
found. The Roman brick was often flat and large--in fact, more like our
common paving tiles, known as foot tiles, only of larger size than like
the bricks that we use. They vary, however, in size, shape, and
thickness. Not a few of them are triangular in shape, and these are
mostly employed as a sort of facing to concrete work, the point of the
triangle being embedded in the concrete and the broad base appearing
outside. After the Roman time, brick making seems to have almost ceased
in England for many centuries.
It is true we find remains of a certain number of massive brick
buildings erected not long after the Norman conquest; but on examination
it turns out that these were put up at places where there had been a
Roman town, and were built of Roman bricks obtained by pulling down
previous buildings. The oldest parts of St. Albans Abbey and portions of
the old Norman buildings at Colchester are examples of this sort.
Apparently, timber was used in this country almost exclusively for
humble buildings down to the 16th century. This is not surprising,
considering how well wooded England was; but stone served during the
same period for important buildings almost to the exclusion of brick.
This is more remarkable, as we find stone churches and the ruins of
stone castles in not a few spots remote from stone quarries, and to
which the stone must have been laboriously conveyed at a time when roads
were very bad and wheel carts were scarce.
About the time of the Tudors, say the reign of Queen Elizabeth, the
making of bricks was resumed in England, and many dwelling houses and
some few churches were built of good brickwork in that and succeeding
reigns. We find in such buildings as Hampton Court Palace, St. James'
Palace, and Chelsea Hospital examples of the use of brickwork in
important buildings near London at later dates. The fire of London, in
1666, gave a sudden check to the use of timber in house building in the
metropolis. Previous to that date the majority of houses had been of a
sort the most ornamental examples of which were copied in "Old London"
at the Colonial Exhibition. The rebuilding after the fire was largely in
brick; and in the suburbs, in the latter part of the 17th and the 18th
centuries, many dignified square brick mansions, with bold, overhanging
eaves and high roofs and carved ornaments, entered through a pair of
florid wrought iron high gates, were built, some few of which still
linger in Hampstead and other suburbs. The war time at the beginning of
this century was a trying time for builders, with its high prices and
heavy taxes, and some of the good-looking brick buildings of that day
turn out to have been very badly built when they are pulled about for
alterations. With the rapid, wonderful increase in population and wealth
in this metropolis during the last 50 years a vast consumption of bricks
has taken place, and a year or two back it was reported by the
commissioners of police that the extensions of London equaled in a year
70 miles of new house property, practically all of brick. Brick were
heavily taxed in the war time which I have referred to, and the tax was
levied before burning.
There was a maximum size for the raw brick, which it was supposed served
to keep bricks uniform, and the expectation was entertained that when
the duty came off, many fancy sizes of bricks would be used. This has
not, however, turned out to be the case. The duty has been taken off for
years; but the differences in the size of bricks in England are little
more than what is due to the different rate of shrinkage of brick earth
under burning. It must not, however, be supposed that they have always,
and in all countries, been of about the same dimensions.
The size and proportions of bricks have varied extremely in different
countries and in the same country at different periods. Some bricks of
unusual shapes have also been employed from time to time. Other
countries besides England possess districts which from various
circumstances have been more or less densely built on, but do not yield
much stone or timber; and, accordingly, brickwork is to be met with in
many localities. Holland and Belgium, for example, are countries of this
sort; and the old connection between Holland and England led to the
introduction among us, in the reign of William III., of the Dutch style
of building, which has been in our own day revived under the rather
incorrect title of Queen Anne architecture. Another great brick district
exists on the plains of Lombardy and the northern part of Italy
generally, and beautiful brickwork, often with enrichments in marble, is
to be found in such cities as Milan, Pavia, Cremona, and Bologna.
Many cities and towns in Northern Germany are also brick built, and
furnish good examples of the successful treatment of the material. In
some of these German buildings, indeed, very difficult pieces of
construction, such as we are in the habit of thinking can only be
executed in stone, are successfully attempted in brick. For example,
they execute large tracery windows in this material. Great brick gables,
often with the stepped outline known as crows' feet, are an excellent
architectural feature of these German brick-built towns. In parts of
France, also, ornamental brickwork was from time to time made use of,
but not extensively. It is not necessary to go very minutely into the
manufacture of bricks; but perhaps I ought to say a word or two on the
subject. Good brick earth is not simple clay, but a compound substance;
and what is essential is that it should burn hard or, in other words,
partly vitrify under the action of heat. The brick earth is usually dug
up in the autumn, left for the frosts of winter to break it up, and
worked up in the early spring.
The moulding is to a very large extent done by hand, sometimes in a wet
mould, sometimes in a dry sanded mould, and the bricks are first
air-dried, often under some slight shelter, as the rain or frost damages
them when fresh made; and then, when this process has made them solid
enough to handle, they are burned, and sorted into qualities. The
ordinary or stock brick of London and the neighborhood presents a
peculiarity the origin of which is not known, and which is not met with,
so far as I know, in other parts. Very fine coal or cinders is mixed
with the brick earth, and when the bricks are fired these minute
particles of fuel scattered through the material all of them burn, and
serve to bake the heart of the brick. Stock bricks are burnt in a clamp
made of the raw bricks themselves with layers of fuel, and erected on
earth slightly scooped out near the middle, so that as the bricks shrink
they drop together, and do not fall over sideways.
Most other varieties of bricks are kiln burnt. A very large number of
inventions for making bricks by machinery have been patented. If you
have occasion to look through the specifications of these patents, you
will find four or five main ideas appearing and reappearing, and only
here and there an invention which is to some extent different from the
others. A great majority of these inventions include machinery for
preparing the clay or brick earth, so that it may be dug up and filled
into a receptacle and worked up, screened from pebbles, and made fit for
use in a short time, so as not to have to wait a whole winter. This is
done in some sort of pug mill. A pug mill is a machine consisting of a
large cylinder with a central shaft passing through it from top to
bottom. Knives or blades are arranged spirally on the shaft, and other
blades project into the interior of the cylinder from the walls of it.
The material, after being screened, is fed into this at the top, and
properly moistened. The shaft is caused to rotate, and the blades divide
and subdivide the material, forcing it always downward, so that it at
last escapes at the bottom of the pug mill in a continuous stream of
moist, well worked up clay, issuing with some force. In one type of
machine this clay stream is forced through a square orifice, from which
it comes out of the section of a brick, and by a knife or wire or some
other means it is cut into lengths.
In another type of machine there is a large revolving drum working on a
horizontal axis, with open moulds all round its edge. The clay enters
these moulds, and there is an arrangement of plungers by which it is
first compressed within the mould and then forced out on to an endless
band or some other contrivance that receives it. A third type of machine
has the moulds in the flat top of a revolving table, which, as it turns,
carries each mould in succession first to a part where it is filled from
the pug mill, next to where its contents are compressed, and lastly to
where they are pushed out for removal. However made, the brick, when
moulded, dried, and burnt, and ready for market, belongs to some one
sort, and is distinguished from other sorts by its size, color, quality,
and peculiarities.
The sorts of brick that are to be met with in the London market are very
varied. To enumerate them all would make a tedious list; to describe
them all would be equally tedious. I will endeavor, however, to give
some idea of the most conspicuous of them. We will begin with that
family of bricks of which the London stock brick is the type. It has
been said these are clamp burnt, and almost all the internal
brickwork--and not a little of the external--of the metropolis is of
stock brickwork. A good London stock brick is an excellent brick for
general purposes, but cannot be called beautiful.
Considering the vast quantity of brickwork done in the metropolis, it is
a matter for congratulation that such sound materials as good stock
bricks, stone lime, and Thames sand are so easily procurable, and can be
had at a price that puts them within the reach of all respectable
builders. When a clamp has been burnt its contents are found to have
been unequally fired, and are part of them underburnt, part well burnt,
part overburnt. They are sorted accordingly into shuffs, grizzles,
stocks of two or three qualities, shippers, and burrs. Several sorts of
malm stocks, which are superior in color and texture, are made, and are
used for facing bricks and for cutting; and what are called paviors,
which are dark and strong bricks, are also made. The London stock is
erroneously, but usually, described as gray. It is really of a pie crust
yellow of various tones. Sometimes it is the same color when cut, but
the hardest stocks are of a dark, dirty purple or brown, or sometimes
nearly black inside. A stock brick is rarely quite square or quite true;
its surface is often disfigured by black specks and small pits, and a
stack of them often looks uninviting; yet a skillful bricklayer, by
throwing out the worst, by placing those of bad colors or much out of
shape in the heart of the wall, and by bringing to the front the best
end or side of those bricks which form part of the face, can always make
the bricks in his work look far better than in the stack. Another
important group is the group of Suffolk and Norfolk bricks, red and
white. These are very largely employed as facing bricks and for arches
and cut mouldings.
Moulded bricks are also to a large extent made of the same material.
These bricks are brought to London in large quantities. They have a
sanded face, are mostly square, true, and of uniform color, but they are
usually porous, soft, and absorbent. Still, they are in great demand as
facing bricks, and the moulded bricks enable the architect to produce
many architectural effects at a moderate outlay. These fields furnish
many sorts of bricks, which are called rubbers, and which are employed
(as malm stocks also are) for arches of the more elaborate sort, where
each brick is cut to its shape and rubbed true, and for mouldings, and
even sometimes for carving.
Mouldings that are formed by cutting the bricks can be got more
perfectly true than when moulded bricks are used; but the expense is
greater, and when it is done the material is less durable, for the
softer sorts of brick are naturally used for cutting, and the moulded
face is less sound than the original burnt face of any brick. Red bricks
are to some extent made in fields within easy reach of London; but the
best come from some distance. Red Suffolk bricks have been alluded to.
There is a considerable importation of red Fareham bricks, brought all
the way from the vicinity of Portsmouth; these are good both in quality
and color. Good red bricks are also now made at Ascot, and are being
used to a considerable extent in the metropolis. A strawberry-colored
brick from Luton has been extensively used at Hampstead. It is hard, and
of a color which contrasts well with stone, but not very pleasing used
alone. Glazed bricks of all colors are obtainable. They are usually very
hard and square, and the use of them where an impervious glazed face is
required, as, for example, in a good stable, is better than the
employment of glazed tiles, in the employment of which there is always a
possibility of part of the lining becoming loose or falling off. There
is a difficulty in obtaining a large quantity (of some colors, at least)
exactly uniform in tint. Bricks with a very hard face, but not glazed,
are obtainable. What is called a washing brick is now made in various
colors, adapted for the lining of interiors, and there are hard bricks
of a very pale straw color, known as Beart's patent bricks, made, I
believe, of gault clay, which were some years ago bought up by the Great
Northern Railway in large numbers. These bricks have the peculiarity of
being pierced with holes about ½ in. in diameter, passing quite through
the brick, and they are extremely hard, partly because these holes
permit the hot air and smoke in the kiln to approach very near to the
interior of the brick. I am of opinion that the glazed or dull qualities
of hard bricks might with great advantage be often introduced into
London streets. What we want is something that will wash. The rough
surface of stocks or Suffolk facing bricks catches the black in the
London atmosphere and gradually gets dark and dull. A perfectly hard
face is washed clean by every shower. A good many years ago I built a
warehouse with stock bricks, and formed the arches, strings, etc., of
bricks with a very hard face, and, as I expected, the effect of time has
been to make these features stand out far better than when they were
fresh; in fact, the only question is whether they have not now become
too conspicuous. To return to the bricks in the London market: we have
firebricks made of fireclay, and almost vitrified and capable of
standing intense heat. These are used for lining furnaces, ovens, flues,
etc.
Then we have almost, if not quite, as refractory a material in
Staffordshire blue bricks, used--in various forms--for paving channels,
jambs of archways, etc. There are also small bricks called clinkers,
chiefly used for stable paving. Dutch clinkers, formerly imported
largely from Holland, were small, rough bricks, laid on edge, and
affording a good foothold for the horse. Adamantine clinkers, made of
gault clay, are much used; they must have chamfered edges, otherwise
they make too smooth a floor for a stable. Many other varieties are
obtainable in London, and are more or less used, but these are the most
prominent. In many parts of England special varieties of brick are to be
found, and every here and there one falls upon a good brickmaker who is
able to produce good moulded or embossed or ornamental bricks, such as
those which have been supplied to me years ago by Mr. Gunton, and more
recently by Mr. Brown, both of Norwich, or by Mr. Cooper, of Maidenhead.
It is of importance to those whose business it is to look after or
engage in building operations, that they should early learn what to look
out for in each material. Of course, a man only becomes a judge of
bricks, or timber, or stone by experience; but he is far better able to
take the benefit of experience when it comes to him if he knows from the
first to what points to direct attention. Wherefore I make no apology
for trying to put before you the points of a good brick, and in doing so
I shall partly quote from a memorandum published now a good many years
ago by the Manchester Society of Architects.
A good brick is uniform in size; standard, 9 by 4½ by 2½ in.; weight
about 7 lb. each = 110 lb. per foot cube; is rectangular, true faced,
but only one end and one side need be smooth; has no print sinking on
either face, but a hollow on one or both beds. When saturated with
water, a brick should not absorb more than 20 per cent, of its own
weight of water, should absorb it reluctantly, and part with it freely
at ordinary temperatures. It should be uniformly burnt, should be sound,
free from cracks, flaws, stones, lumps of any kind, but especially lumps
of lime, should be of a good color for its sort (whether red, yellow, or
white), should have a metallic clang when two bricks are struck
together; when broken should be sound right through, should be tough and
pasty in texture, not granular, and should require repeated blows to
break it, rather than one hard blow (such bricks will withstand cartage
and handling best). So much for bricks. To make brickwork, however,
another ingredient is required--namely, mortar or cement.
All mortars and, in fact, all the cementing materials used (except
bituminous ones) in bricklaying have lime as their base, and depend upon
the setting quality of quicklime, which has to be mixed with sand or
some suitable substitute for it, to make mortars. Limes and cements are
far too wide a subject to be dealt with as part of an evening's lecture
on another topic, and no doubt they will hereafter form the subject of a
lecture or lectures. To-night I propose only to remind you that there
are such substances as these, and that they possess certain qualities
and are obtainable and available for the bricklayer's purposes, without
attempting an investigation into the chemistry of cements, or their
manufacture, etc. Ordinarily, brickwork may be divided into brickwork in
mortar and in cement; but there are many qualities of mortar and several
sorts of cement. Mortar made with what are called fat or rich
limes--that is to say, nearly pure lime, such as is got by calcining
marble or pure chalk--sets slowly, with difficulty, and is rarely
tenacious. Burnt clay or brick reduced to powder improves the setting of
such lime, especially if the two materials be calcined together; so will
an admixture of cement. Mortar made with what is known as slightly
hydraulic lime, that is to say, lime containing a small proportion of
clay, such as the gray stone lime of Dorking, Merstham, and that
neighborhood, sets well, and is tenacious and strong. Mortar made with
hydraulic lime, that is to say, lime with a considerable admixture of
clay, such as the lias lime, sets under water or in contact with wet
earth. It is best to use this lime ground to powder, and not to mix so
much sand with it as is used with stone lime. A sort of mortar called
selenitic mortar, the invention of the late General Scott, has been made
use of in many of the buildings of the School Board for London, and was
first employed on a large scale in the erection of the Albert Hall. The
peculiarity consists in the addition of a small dose of plaster of Paris
(sulphate of lime) very carefully introduced and intimately mixed. The
result is that the mortar so made sets rapidly, and is very hard.
It is claimed that a larger proportion of sand can be used with
selenitic lime than with ordinary, thus counterbalancing the extra
expense occasioned by royalty under the patent and special care in
mixing. When a limestone contains 20 to 40 per cent, of clay, it becomes
what is called a cement, and its behavior is different from that of
limestones with less clay. Ordinary limestones are, as you know,
calcined in a kiln. The material which comes from the kiln is called
quicklime, and, on being dosed with water, it slakes, and crumbles to
powder, and in the state of slaked lime is mixed up with mortar. Cement
stones are also calcined; but the resulting material will not fall to
pieces or slake under water. It must be ground very fine, and when
moistened sets rapidly, and as well under water as in air, and becomes
very hard and is very tenacious. Brickwork in mortar will always settle
and compress to some extent. Not so brickwork in cement, which
occasionally expands, but is never to be compressed. This quality and
the rapid setting, tenacity, and strength of brickwork in cement make it
a most valuable material to use in those buildings or parts of a
building where great steadiness and strength are wanted, and in sewage
and dock work, where there is water to contend with. A good many cements
made from natural stones used to be employed, such as Medina, Harwich,
Atkinson's, or Roman cement. The last named is the only one which is now
much employed, except locally. It has the quality of setting with
exceptional rapidity, and is on that account sometimes the best material
to employ; but for almost every purpose the artificial compound known as
Portland cement is preferable.
Portland cement is made largely near Rochester. Its materials are simple
and cheap. They may, without much departure from the truth, be said to
be Thames mud and chalk; but the process of manufacture requires care
and thoroughness. The article supplied, when of the best quality, has
great strength, and is quick setting, and is far better than what was
manufactured from stones in which the ingredients existed in a state of
nature. In England we slake our lime and make use of it while it is
fresh; but it may interest you to know that the custom in Italy and
parts of France is different. There it is customary to slake the lime
long before it is wanted, and to deposit it in a pit and cover it up
with earth. In this condition it is left for months--I believe in Italy
for a year--and when taken out it is stiff, but still a pasty substance.
It is beaten, and more water added, and it is then made into mortar with
sand. It is claimed for mortar made in this way that is exceptionally
strong.
Now that we have considered bricks and partly considered mortar, it
remains to pay some attention to brickwork. The simplest and most
familiar work for a bricklayer to do is to build a wall. In doing this
his object should be to make it as stout as possible for the thickness,
and this stoutness can only be obtained by interlacing the bricks. If
they were simply laid on the top of each other, the wall would be no
more than a row of disconnected piles of bricks liable to tumble down.
When the whole is so adjusted that throughout the entire wall the joints
in one course shall rest on solid bricks and shall be covered by solid
bricks again--in short, when the whole shall break joint--then this wall
is said to be properly bonded, and has as much stability given to it as
it can possibly possess. There are two systems of bonding in use in
London, know as English bond and Flemish bond. English bond is the
method which we find followed in ancient brickwork in this country.
In this system a course of bricks is laid across the wall, showing their
heads at the surface, hence called "headers," and next above comes a
course of bricks stretching lengthways at the wall, called stretchers,
and so on alternately. With the Dutch fashions came in Flemish bond, in
which, in each course, a header and a stretcher alternate. In either
case, at the corners, a quarter-brick called a closer has to be used in
each alternate course to complete the breaking joint. There is not much
to choose between these methods where the walls are only one brick
thick. But where they are thicker the English has a decided advantage,
for in walls built in Flemish bond of one and a half brick thickness or
more there must be a few broken bricks, or bats, and there is a strong
temptation to make use of many. If this takes place, the wall is
unsound.
Many of the failures of brickwork in London houses arise from the
external walls, where they are 1½ bricks thick, being virtually in two
skins; the inner 9 in. does the whole of the work of supporting floors
and roof, and when it begins to fail, the outer face bulges off like a
large blister. I have known cases where this had occurred, and where
there was no header brick for yards, so that one could pass a 5 ft. rod
into the space between the two skins and turn it about. This is rather
less easy to accomplish with English bond, and there are other
advantages in the use of that bond which make it decidedly preferable,
and it is now coming back into very general use. There are some odd
varieties of bond, such as garden bond and chimney bond. But of these I
only wish to draw your attention to what is called cross bond. The name
is not quite a happy one. Diagonal bond is hardly better. The thing
itself is to be often met with on the Continent, and it is almost
unknown here. But it would be worth introducing, as the effect of it is
very good.
French cross bond, otherwise diagonal bond _(liaison en croix)_, is
English bond, but with the peculiarity that in every fourth course one
header is made use of in the stretcher course at the quoin. The result
is that the stretchers break joint with each other, and all the joints
range themselves in diagonal lines, and if in any part of the work
headers of a different brick are introduced, the appearance of a cross
is at once brought out; and even without this the diagonal arrangement
of joints is very perceptible and pleasing.
Besides wall building, the bricklayer has many other works to perform.
He has to form fireplaces, flues, chimneys, and the flat trimmer arches
which support the hearth, and has to set the stove, kitchen range,
copper, etc., in a proper manner. He has to form various ornamental
features and much else, some of which we shall have an opportunity of
noticing rather later. The strangest business, however, which is
intrusted to the bricklayer is building downward--by the method known as
underpinning--so that if a foundation has failed, a sounder one at a
greater depth may be reached; or if a basement is required under an
existing building which has none, the space may be excavated and the new
walls built so as to maintain the old.
This work has to be done with great caution, and bit by bit, and is
usually left to experienced hands. The mode in which the mortar joints
of a brick wall are finished where they show on the external or internal
face is a matter worth a moment's attention. It is important that the
joints of the work shall be so finished as to keep out wet and to be as
durable as possible, and it is desirable that they should improve, or at
any rate not disfigure, the appearance of the work.
The method which architects strongly advocate is that the joints shall
be struck as the work proceeds--that is, that very shortly after a brick
is laid, and while the mortar is yet soft, the bricklayer shall draw his
trowel, or a tool made for the purpose, across it, to give it a smooth
and a sloping surface. This is best when the joint is what is called a
weather joint--i.e., one in which the joint slopes outward. Sloping it
inward is not good, as it lets in wet; finishing it with a hollow on the
face is often practiced, and is not bad. Bricklayers, however, most of
them prefer that the mortar joints should be raked out and pointed--that
is to say, an inch or an inch and a half of the mortar next the outer
face be scratched out and replaced with fresh mortar, and finished to a
line.
In cases where the brickwork is exposed to frost, this proceeding cannot
be avoided, because the frost damages the external mortar of the joints.
But the bricklayers prefer it at all seasons of the year, partly because
brickwork is more quickly done if joints are not struck at the time;
partly because they can, if they like, wash the whole surface of the
work with ocher, or other color, to improve the tint; and partly
because, whether the washing is done or not, it smartens up the
appearance of the work. The misfortune is that this pointing, instead of
being the edge of the same mortar that goes right through, is only the
edge of a narrow strip, and does not hold on to the old undisturbed
mortar, and so is far less sound, and far more liable to decay. There is
a system of improving the appearance of old, decayed work by raking out
and filling up the joint, and then making a narrow mortar joint in the
middle of this filling in, and projecting from the face. This is called
tuck pointing. It is very specious, but it is not sound work.
Brick arches are constantly being turned, and of many sorts. An arch
consists of a series of wedge shaped blocks, known as voussoirs,
arranged in a curve, and so locking one another together that unless the
abutments from which the arch springs give way, it will not only carry
itself, but sustain a heavy load. It is a constant practice to cut
bricks to this shape and build them into an arch, and these are
sometimes cut and rubbed; sometimes, when the work is rougher, they are
axed. But in order to save the labor of cutting, arches are sometimes
turned with the bricks left square, and the joints wedge shaped. In this
case the rings should be only half a brick each, so that the wedge need
not be so very much wider at back than at face, and they are set in
cement, as that material adheres so closely and sets so hard. Arches of
two or more half-brick rings in cement are good construction, and are
also used for culvert work.
A less satisfactory sort of arch is what is called the flat arch. Here,
instead of being cambered as it ought to be, the soffit is straight; but
the brickwork being deep, there is room enough for a true arch that does
the work, and for useless material to hang from it. These arches are
generally rubbed or axed, and are very common at the openings of
ordinary windows. But no one who has studied construction can look at
them without a kind of wish for at least a slight rise, were it only two
inches. Sometimes when these straight arches are to be plastered over
they are constructed in a very clumsy manner, which is anything but
sound, and from time to time they give way. The weight of brickwork, of
course, varies with the weight of the individual bricks. But stock
brickwork in mortar weighs just about one hundred weight per cubic foot,
or 20 cubic feet to the ton. In cement it is heavier, about 120 lb. to
the cubic foot.
The strength of brickwork depends of course on the strength of the
weakest material--i.e., the mortar--though when it is in cement the
strength of brickwork to withstand a weight probably approaches that of
the individual bricks. Some experiments quoted in Rivington's Notes give
the following as the crushing weight per foot--that is to say, weight at
which crushing began--of piers having a height of less than twelve times
their diameter:
Tons per
foot.
Best stocks, set in Portland cement and
sand 1 to 1, and three months old. 40
Ordinary good stocks, three months old. 30
Hard stocks, Roman cement and sand 1 to 1,
three months old. 28
Hard stocks, lias lime, and sand 1 to 2,
and six months old. 24
Hard stocks, gray chalk lime, and sand,
six months old. 12
The rule given in popular handbook, that brickwork in mortar should not
have to carry more than three tons per superficial foot, and in cement
more than five tons, is probably sound, as in no building ought the load
to approach the crushing point, and, indeed, there are many sorts of
foundations on which such a load as five tons per foot would be too
great to be advisable.
It is a rather interesting inquiry, whenever we are dealing with a
building material, if we ask what can we best do with it, and for what
is it ill fitted. The purposes for which brick can be best used depend,
of course, upon its qualities. Speaking generally, such purposes are
very numerous and very various, especially the utilitarian purposes,
though rich and varied ornamental work can also be executed in
brickwork.
Perhaps the most remarkable quality of brickwork is that it can be
thrown into almost any shape. It is in this respect almost like a
plastic material, and this peculiarity it owes chiefly to the very small
size of each brick as compared with the large masses of the brickwork of
most buildings. Stone is far less easily dealt with than brick in this
respect. Think for a moment of the great variety of walls, footings,
piers, pilasters, openings, recesses, flues, chimney breasts, chimney
shafts, vaults, arches, domes, fireproof floors, corbels, strings,
cappings, panels, cornices, plinths, and other features met with in
constant use, and all formed by the bricklayer with little trouble out
of the one material--brickwork! A little consideration will convince you
that if the same material furnishes all these, it must be very plastic.
As a limitation we ought to note that this almost plastic material
cannot be suddenly and violently dealt with--that is to say, with the
exception of some sorts of arches, you cannot form any abrupt or
startling feature in brickwork, and you are especially limited as to
projections.
If you wish to throw out any bold projection, you may support it on a
long and sloping corbel of brickwork. But if there is not room for that,
you must call in some other material, and form the actual support in
stone, or terra cotta, or iron, and when you have gained your
projection, you may then go on in brickwork if you like.
Brick cornices should be steep, but cannot be bold, and so with other
ornamental and structural features. A noteworthy property of brickwork,
and one of immense value, is that it is thoroughly fireproof; in fact,
almost the only perfectly fireproof material. There is an interesting
account of the great fire of London by one of the eye witnesses, and
among the striking phenomena of that awful time he notes that the few
brick buildings which existed were the only ones able to withstand the
raging fire when it reached them.
In our own day a striking proof of the same thing was given in the great
fire in Tooley street, when Braidwood lost his life. I witnessed that
conflagration for a time from London Bridge, and its fury was something
not to be described. There were vaults under some of the warehouses
stored with inflammable materials, the contents of which caught fire and
burnt for a fortnight, defying all attempts to put them out. Yet these
very vaults, though they were blazing furnaces for all that time, were
not materially injured. When the warehouses came to be reinstated, it
was only found necessary to repair and repoint them a little, and they
were retained in use. The fact is that the bricks have been calcined
already, so has the lime in the mortar, and the sand is not affected by
heat, so there is nothing in brickwork to burn. Against each of these
good qualities, however, we may set a corresponding defect.
If brickwork is easily thrown into any shape, it is also easily thrown
out of shape. It has little coherence or stability, less than masonry
and very considerably less than timber. If any unequal settlement in the
foundation of a brick building occurs, those long zigzag cracks with
which we in London are only too familiar set themselves up at once; and
if any undue load, or any variation in load, exists, the brickwork
begins to bulge. Any serious shock may cause a building of ordinary
brickwork to collapse altogether, and from time to time a formidable
accident occurs owing to this cause. The fact is, the bricks are each so
small compared to the mass of the work, and the tenacity or hold upon
them of even fairly good lime mortar is so comparatively slight, that
there is really but little grip of one put upon another.
Persons who have to design and construct brick buildings should never
forget that they have to be handled with caution, and are really very
ticklish and unstable. One or two of the methods of overcoming this to
some extent may be mentioned. The first is the introduction of what is
called bond. At the end of the last century it was usual to build in, at
every few feet in height, bond timbers, which were embedded in the heart
of the walls. If these had always remained indestructible, they would no
doubt have served their purpose to some extent. Unfortunately, timber
both rots and burns, and this bond timber has brought down many a wall
owing to its being destroyed by fire, and has in other cases decayed
away, and caused cracks, settlements, and failures.
The more modern method of introducing a strong horizontal tie is to
build into the wall a group of bands of thin iron, such as some sorts of
barrels are hooped with--hence called hoop iron. The courses of bricks
where this occurs must be laid in cement, because iron in contact with
cement does not perish as it does in contact with mortar.
If in every story of a building four or five courses are thus laid and
fortified, a great deal of strength is given to the structure. Another
method, which has rather fallen into disuse, is grouting. This is
pouring liquid mortar, about the consistency of gruel, upon the work at
about every fourth course. The result is to fill up all interstices and
cavities, and to delay the drying of the mortar, and brickwork so
treated sets extremely hard. I have seen a wall that had been so treated
cut into, and it was quite as easy to cut the bricks (sound ones though
they were) as the mortar joints.
Grouting is objected to because it interferes with the good look of the
work, as it is very difficult to prevent streaks of it from running down
the face, and it is apt to delay the work. But it is a valuable means of
obtaining strong brickwork. Another and a more popular method is to
build the work in cement, now usually Portland cement. This, of course,
makes very strong, sound work, and does not involve any delay or dirt
like grouting, or the introduction of any fresh material like hoop iron.
But it, of course, adds to the expense of the work considerably, as
cement is much more costly than lime. I ought to add that the advocates
of Scott's selenitic mortar claim that it not only sets quickly and
hard, but that it is extremely tenacious, and consequently makes a much
more robust wall than ordinary mortar. I dare say this is true; but I
have not happened to see such a wall cut into, and this is the best test
of solidity.
The second deficiency in brickwork which I am bound to notice is that,
though it is very fireproof, it is far from being waterproof. In an
exposed situation rain will drive completely through a tolerably stout
brick wall. If water be allowed to drop or fall against it, the wall
will become saturated like a sponge. If the foot of a wall becomes wet,
or if the earth resting against the lower parts of it be moist, water
will, if not checked, rise to a great height in it, and if the upper
part of the wall be wet, the water will sink downward. With most sorts
of brick the outer face absorbs moisture whenever the weather is moist;
and in time the action of the rain, and the subsequent action of frost
upon the moisture so taken up, destroys the mortar in the joints, which
are to be seen perfectly open, as if they had been raked out, in old
brickwork, and in some cases (happily not in many) the action of weather
destroys the bricks themselves, the face decaying away, and the brick
becoming soft.
Against this serious defect in our staple building material a series of
precautions have been devised. Damp rising from the foot of the wall, or
from earth lying round its base, is combated by a damp course--a bed of
some impervious material going through the wall. Damp earth may be kept
off by surrounding the walls with an open area or a closed one--usually
termed a dry area. Damp against the face of the walls may be partly
combated by a careful selection of a non-absorbent brick with a hard
face and by struck joints. But it is most effectually kept at bay by the
expedient of building the wall hollow; that is to say, making the
external wall of the house to consist of two perfectly distinct walls,
standing about 2 in. apart, and held together by ties of earthenware or
iron. The result is that the moisture blowing through the outer skin
does not pass the cavity, but trickles down on the inner face of the
outer wall, while the inner wall remains dry. The ties are constructed
of shapes to prevent their conducting water themselves from without to
the inner wall. In addition to this, a series of slates forming an
intermediate protection is sometimes introduced, and forms an additional
and most valuable screen against weather. Sometimes, the two skins of
the wall are closer together--say ¾ in.--and the space is filled with a
bituminous material.
A substance of a bituminous nature, called hygeian rock, has been of
late years introduced, and is being extensively used for this purpose;
it is melted and poured into the open space hot, and quickly hardens.
The use of such a material is open to the objection that no air can pass
through it. The rooms of our houses are receiving air constantly through
the walls, and much of the constant current up our chimneys is supplied,
to our great advantage, in this very imperceptible manner. The house
breathes, so to speak, through the pores of its brickwork. When this is
rendered impossible, it seems clear that fiercer draughts will enter
through the chinks and crevices, and that there will be a greater demand
upon flues not in use, occasioning down draught in the chimneys.
Another mode of keeping out weather is to cement the face of the
brickwork. But this hides up the work, and so tends to promote bad work,
besides being often very unsightly.
Among other peculiarities of brickwork are the facilities for
introducing different colors and different textures of surface which it
presents, the ease with which openings and arches can be formed in it,
the possibility of executing ornament and even carving, and the ease
with which brickwork will combine with other building materials. It
cannot be well made use of for columns, though it may readily enough be
turned into piers or pilasters. It cannot, generally speaking, with
advantage be made use of for any large domes, though the inner dome of
St. Paul's and the intermediate cone are of brick, and stand well. But
it is an excellent material for vaulting arcades and all purposes
involving the turning of arches.
Brickwork must be said to be durable, but it requires care. If not of
the best, brickwork within the reach of the constant vibration caused by
the traffic on a railway seems to be in danger of being shaken to
pieces, judging from one or two instances that have come under my own
observation. The mortar, and even in some cases the bricks themselves,
will rapidly deteriorate if moisture be allowed to get into the heart of
a brick wall, and in exposed situations this is very apt to happen. Care
should always be taken to keep the pointing of external brickwork in
good order, and to maintain all copings and other projections intended
to bar the access of water coming down from above, and to stop the
overflowing of gutters and stack pipes, which soon soaks the wall
through and through.
Of course, if there is a failure of foundations, brickwork, as was
pointed out earlier, becomes affected at once. But if these be good, and
the materials used be sound ones, and if the other precautions just
recommended be taken, it will last strong and sturdy for an immense
length of time. In some cases, as for example in the Roman ruins, it has
stood for 1,500 years under every possible exposure and neglect, and
still shows something of a sturdy existence after all, though sadly
mutilated. If we now return to the question, What can be well done in
brickwork? no better answer can be given than to point to what has been
and is being done, especially in London and within our own reach and
observation.
Great engineering works, such as railway viaducts, the lining of railway
tunnels, the piers and even the arches of bridges, sewage works, dock
and wharf walls, furnace chimneys, and other works of this sort are
chiefly done in brickwork. And notwithstanding that iron is far more
used by the engineer for some purposes and concrete for others now than
formerly, still there is a great field for brickwork. The late Mr.
Brunel, who was fond of pushing size to extremes, tried how wide a span
he could arch over with brickwork. And I believe the bridge which
carries the G.W.R. over the Thames at Maidenhead has the widest arch he
or any other engineer has successfully erected in brick. This arch has,
it is stated, a span of 128 ft. It is segmental, the radius being 169
ft., and the rise from springing to crown 24 ft., and the depth of the
arch 5 ft. 3 in. Nowadays, of course, no one would dream of anything but
an iron girder bridge in such a position. Mr. Brunel's father, when he
constructed the Thames Tunnel, lined it with brickwork foot by foot as
he went on, and that lining sustained the heavy weight of the bed of the
river and the river itself.
If you leave London by either of the southern lines, all of which are at
a high level, you go for miles on viaducts consisting of brick arches
carried on brick walls. If you leave by the northern lines, you plunge
into tunnel after tunnel lined with brickwork, and kept secure by such
lining. Mile after mile of London streets, and those in the suburbs,
present to the eye little but brick buildings; dwelling houses, shops,
warehouses, succeed one another, all in brickwork, and even when the eye
seems to catch a change, it is more apparent than real.
The white mansions of Tyburnia, Belgravia, South Kensington, and the
neat villas of the suburbs are only brickwork, with a thin coat of
stucco, which serves the purpose of concealing the real structure--often
only too much in need of concealment--with a material supposed to be a
little more sightly, and certainly capable of keeping the weather out
rather more effectually than common brickwork would.
More than this, such fine structures, apparently built entirely of
stone, as are being put up for commercial purposes in the streets of the
city, and for public purposes throughout London, are all of them nothing
more than brick fabrics with a facing of masonry. Examine one of them in
progress, and you will find the foundations and vaults of brickwork, and
not only the interior walls, but the main part of the front wall,
executed in brickwork, and the stone only skin deep. There are, however,
two or three ways of making use of brickwork without covering it up, and
of gaining good architectural effects thereby, and to these I beg now to
direct your attention.
The architect who desires to make an effective brick building, which
shall honestly proclaim to all the world that it is of brick, may do
this, and, if he will, may do it successfully, by employing brickwork
and no other material, but making the best use of the opportunities
which it affords, or he may erect his building of brickwork and stone
combined, or of brickwork and terra cotta. Mr. Robson, till lately the
architect to the School Board for London, has the merit of having put
down in every part of the metropolis a series of well contrived and well
designed buildings, the exterior of which almost without exception
consists of brickwork only.
If you examine one of his school-houses, you will see that the walls are
of ordinary stock brickwork, but usually brightened up by a little red
brick at each angle, and surmounted by well contrasted gables and with
lofty, well designed chimneys, rising from the tiled roof. The window
openings and doorways are marked by brickwork, usually also red, and
sometimes moulded, and though I personally must differ from the taste
which selected some of the forms employed (they are those in use in this
country in the 17th and the last centuries), I cordially recognize that
with very simple and inexpensive means exceedingly good, appropriate,
and effective buildings have been designed.
Among examples of architecture wholly, or almost wholly, executed in red
brick, I cannot pass over a building built many years ago, little known
on account of its obscure situation, but a gem in its way. I allude to
the schools designed by Mr. Wilde, and built in Castle street, Endell
street.
Of buildings where a small amount of stone is introduced into brickwork
we have a good many fine specimens in London. One of the best--probably
the best--is the library in Lincoln's Inn Fields. This is a large and
picturesque pile, built under Mr. Hardwick, as architect, in red brick,
with patterns in the blank parts of the walls done in black brick. It
has splendid moulded brick chimneys, and the mullions of the windows,
the copings, the entrances, and some other architectural features done
in stone. The building is a good reproduction of the style of building
in Tudor times, when, as has been already mentioned, brickwork was taken
into favor.
Another building of the same class, but not so good, is the older part
of the Consumption Hospital, at Brompton. Brickwork, with a little
stone, has been very successfully employed as the material for churches,
and in many such cases the interior is of unplastered brickwork. Such
churches often attain, when designed by skillful hands, great dignity
and breadth of effect. St. Albans, Holborn; the great church designed by
Mr. Butterfield, in Margaret street; Mr. Street's church near Vincent
square, Westminster; and several churches of Mr. Brooks', such as he was
kind enough to enable me to illustrate tonight, may be mentioned as
examples of the sort. Mr. Waterhouse has built an elaborate
Congregational church at Hampstead, which shows the use with which such
effects of color may be obtained in interiors, and has kindly lent some
drawings. Mr. Pearson's church at Kilburn may also be referred to as a
fine example of brick vaulting. Brick and terra cotta seem to have a
natural affinity for one another. Terra cotta is no more than a refined
brick, made of the same sort of material, only in every respect more
carefully, and kiln baked. Its similarity to brick is such that there is
no sense of incongruity if moulded or carved brickwork and terra cotta
are both employed in the same building, and this can hardly be said to
be the case if the attempt is made to combine ornamental brickwork and
stone ornaments.
At South Kensington, a whole group of examples of brickwork with terra
cotta meet us. The Natural History Museum, the finest of them all, is
hardly fit for our present purpose, as it is as completely encased in
terra cotta as the fronts of the buildings in this avenue are in stone.
But here are the Albert Hall, a fine specimen of mass and effect; the
City and Guilds Institute; the College of Music, and some private houses
and blocks of flats, all in red brick with terra cotta, and all showing
the happy manner in which the two materials can be blended. In most of
them there is a contrast of color; but Mr. Waterhouse, in the Technical
Institute, has employed red terra cotta with red bricks, as he also has
done in his fine St. Paul's School at Hammersmith, and Mr. Norman Shaw
has, in his fine pile of buildings in St. James' street. This
combination--namely, brick and terra cotta--I look upon as the best for
withstanding the London climate, and for making full use of the
capabilities of brickwork that can be employed, and I have no doubt that
in the future it will be frequently resorted to. Some of those examples
also show the introduction of cast ornaments, and others the employment
of carving as means of enriching the surface of brick walls with
excellent effect. Here we must leave the subject; but in closing, I
cannot forbear pointing to the art of the bricklayer as a fine example
of what may be accomplished by steady perseverance. Every brick in the
miles of viaducts or tunnels, houses, or public buildings, to which we
have made allusion, was laid separately, and it is only steady
perseverance, brick after brick, on the part of the bricklayer, which
could have raised these great masses of work. Let me add that no one
brick out of the many laid is of no importance. Some time ago a great
fire occurred in a public asylum, and about £2,000 of damage was done,
and the lives of many of the inmates endangered. When the origin of this
fire came to be traced out, it was found that it was due to one brick
being left out in a flue. A penny would be a high estimate of the cost
of that brick and of the expense of laying it, yet through the neglect
of that pennyworth, £2,000 damage was done, and risk of human life was
run. I think there is a moral in this story which each of us can make
out if he will.
* * * * *
A fireproof whitewash can be readily made by adding one part silicate of
soda (or potash) to every five parts of whitewash. The addition of a
solution of alum to whitewash is recommended as a means to prevent the
rubbing off of the wash. A coating of a good glue size made by
dissolving half a pound of glue in a gallon of water is employed when
the wall is to be papered.
* * * * *