86 THE BUILDING NEWS. Fes. 2, 1872.
steamship, and many other works to which
the term ‘ great”’ was not inapplicable if we
limit its meaning to size. Sir Isambard
Brunel was so confident of the use to be made
of brickwork in cement, strengthened with
hoop-iron bond, that he proposed to con-
struct arches without centreing, where there
was to be more than one, by beginning to turn
them by equal additions on each side of a
pier, inserting hoop-iron bond longitudinally
in the spandrels as the work proceeded. The
cement he used was one that set very quickly,
so that he was able to add course after course
with tolerable quickness, always preserving
on each side of the pier an equal number of
courses until he reached the crown of the
arch; and supposing another half-arch to have
been in progress from the opposite pier or
abutment to meet it, the arch would haye
been keyed in, or, rather, it would have re-
quired no key, for although in the form ofan
arch, the structure wasreallya beam, depend-
ing for its stability on the tensile strength of
the hoop-iron in the upper part, and on the
compressive strength of the brick at and near
the springing. de did not propose to turn
the arch of the full width at once, but to first
turn a rib of about four feet in width, using
a templet in the manner in which it is used
in building a curved wall, to preserve the form
of the arch, and, when the rib had been
turned, to add to its width on each side until
the required width had been attained.
Brickwork is measured by the cubic yard
in structures such as bridges, retaining walls,
and other large masses, and in the midland
and northern counties by the square yard of
walling, the thickness being stated as one
brick, brick and a half, two bricks, &c., for
each of which builders have their prices per
square yard. But in the London district
walling is measured by the rod, and builders
and contractors have become so accustomed to
measurement by the rod that other kinds
of work are sometimes measured also by the
rod. A cubic yard contains 27 cubicfeet; a
square yard 9 square feet, Arodis 53 yards
in length, or 163ft.; a square rod, therefore,
contains 272} square feet. A rod of brick-
work is 2724 square feet of the thickness of
a brick and a half, or 154in., and as the Ht.
is neglected in practice, the rod contains
272ft. x 1fft. = 306 cubic feet, = 111 cubic
yards. In walling of various thicknesses the
quantity is reduced to the standard thickness
of a brick and a half, and is estimated at
‘‘per rod reduced.” Thus, in measuring
three walls, one of which is 9in. thick, another
13fin., and the other 18in. thick, the area of
each is taken and multiplied into the number
of half bricks in the thickness ; the wall 9in.
thick by 2, the wall 14in. thick by 3, and
the wall 18in. thick by 4; the sum of these
divided by 3 shows the number of rods of
brickwork reduced to the standard thickness.
If odd feet remain over a number of rods the
quantity is stated in rods and feet, or in rods
and fractions of a rod, or in rods and
decimals. Thus, if a wall be measured as
50ft. long, 9ft. high, and one brick thick ;
another 30ft. long, 12ft. high, and a brick
and a half thick; and another 30ft. long,
18ft. high, and two bricks thick, the measure-
ment would stand thus—
30x 9X2 = 540 30 x 12 * 3 = 1080 30 X 18 x 4 = 2160 3) 3780
1260 square feet a brick and a half thick, and 1260 172 372 I79 212 LIZ 4-63 rods. Another method of reducing dimensions to the standard thickness is first to find the number of cubic feetin the work, and then to multiply them 8 times, and divide the product by 9, those being numbers which are proportionate to 12 and 13} respectively, rods, = 433 rods, 68
4rods 172ft. = 4
or, in other words, one-ninth is deducted from the number of cubic feet to reduce them to the standard thickness; thus, taking the former dimensions—
S0ft. SiS 9) an = 202'5 cub, tt
30,, X 12, X 134,, = 405 3
80,;, 18S), = SLO 4
14175,
8
9) 11340
1260 sq. ft.
a brick and a half thick, as before.
In some counties in England, where stone
walling is cheaper than brickwork, and also
in Ireland, the custom is to measire by the
perch. A perch is then understood to be a
length of wall of 7 yards, or 21ft., 1ft. high
and 18in. thick, that thickness being the
usual one for stone walls. If these dimen-
sions are reckoned up they come to 314 cubic
feet. When the standard thickness of walls
is 18in. it is convenient to take an even num-
ber of yards or feet, say 7 or 21, for each foot
in height, and to call that a perch—in some
places a rod, for in olden times a rod, pole,
or perch were synonymous terms for the same
quantity. But in measuring brickwork by
the same standard the difficulty has been that
it has been about twice as expensive, so, in
measuring brickwork, while adhering to the
standard of the perch, or rod of 7 yards, the
standard thickness has been proportionately
reduced, and for brickwork a perch or rod of
walling is taken to be Qin. thick, which gives
a cubical measurement of 153 cubic feet.
These local customs are very awkward, and
insuch aunited kingdomas this of Great Britain
and Ireland one would think some more
reasonable standard of measurement would
be established ; for not only do the different
counties in England differ, but, while we
adopt the Irish method of measurement by
the perch of walling in some counties, we
know nothing of it in others. Then in
measuring by the rod, as in the London dis-
trict, and reducing all thicknesses of walling to
one standard of a brick and a half, it is but a
rough method, for the proportion of face-
work to cubic contents is greater in thin than
in thick walls, and ought in some measure to
govern the price of the work. Then in re-
ducing thicknesses to 1} brick, a brick is as-
sumed to be Qin. long and 44in. wide,
but bricks of different sorts vary so much
in size that a wall may be considerably
thicker or thinner than the assumed
thickness, and the bricklayer’s work will
be influenced by that. Now, a yard is
understood all over the country to be 3 feet,
or 36 inches; why, therefore, should not a
cubic yard be the standard for all common
work, and a cubic foot for ornamental work,
adding in both cases the superficial measure-
ment of the face-work? A builder who has a
large business will probably be quite satisfied
with things as they are, because at the year’s
end he will have done a sufficient amount of
work of various kinds to bring to bear the
rule of averages, and if he should have lost
something in some cases he will probably
have gained as much in others; but that is
accidental to his large business, and ought
not to be reckoned upon in fixing standards
of measurement. A yard certainly has the
disadvantage of being small, perhaps petty ;
then let a name be invented for a measure-
ment of 10 eubic yards, which would ap-
proach in bulk nearly to a rod.
‘The number of bricks required to build a
given cubic capacity of work varies consider-
ably with the different kinds of bricks. It is
stated in Dobson’s treatise on the manufac-
ture of bricks and tiles that bricks are made
at Nottingham as large as 9} X 48 x 3 1-16,
and that they weigh Slb.; that Suffolk bricks
are 9F x 415-16 x 3} in the mould, and that
they shrink in drying 7 inch in the length.
If we take a proportionate shrinkage in the
width and thickness, the dimensions of the
brick would be 9 x 43 x 8. The weight is
stated to be 6lb. Staffordshire blue bricks
are stated to weigh 8lb. loz., and to have a
specific gravity of 1-861. It is stated that
London stock bricks are 83 x 41 x 23, and
that they weigh 5lb.
The average thickness of all bricks is pro-
bably 2} inches, and when that is the actual
average thickness of any particular sort of
bricks, four courses to the foot in height
makes the best work. In that case it requires
about 350 bricks per cubic yard of work ; but
taking London stocks at only 24 inches thick,
four courses to a foot in height would make
the bed joints too thick ; a greater number of
bricks, therefore, is required. A rod of brick-
work requires 4,500 stocks, allowing for
waste; but in house-building, the flues,
which are measured solid, and the bond
timber, wood bricks, &c., which are measured
in, sufficiently allow for waste, and in house-
building a rod of brickwork requires 4,300
stocks.
The weight of the brickwork varies, of
course, with the specific gravity of the bricks,
and is influenced by their individual size. If
we take the dimensions and weights before
stated, we find the specific gravity of Suffolk
bricks to be 1:398; of Nottingham bricks,
1:637 ; of London stocks, 1:°654, and of
Staffordshire blue bricks, 1-861.
On the whole the weight of brickwork in
mortar exposed to the weather may be said to
average 1 cwt. per cubic foot, or 27 cwt. per
cubic yard, or about 15 tons per rod.
The quantity of mortar is about one-fifth of
the whole mass when the bricks are straight
and square, and are well and closely laid, but
with the ill-shaped bricks sometimes used
one-quarter of the whole mass is mortar.
———
DECORATIVE PROCESSES.
GILDING.
By an Exrerrencep WorKMAN.
(Continued from page 50.)
ILDING in oil, as we have before said,
is not confined to frame gilding, but
has avery wide application. It requires a
different preparation of ground to that which
has been described as used by the frame
gilder, although gilding on the enrichments or
ornamental parts of a ceiling or cornice which
is finished in distemper willrequire to be in
some degree prepared in the same manner to
receive the oil gold size. When the ornamental
parts of a distemper ceiling have to be part-
gilt, those parts will have to be done once
with two or three coats of clear-cole or one
coat of strong size, in order to prevent the
oilfrom sinking into the body of the distem-
per, and to prevent its spreading and making
ragged edges. When the distemper size is
dry, the oil gold size should (in etching) be
cut in sharp and clear, and about a sixteenth
of an inch inside the margin of the coating of
parchment size previously laid on, so as to
prevent the danger of its running into the
distemper. When the gilding isdone it will
require to be backed or brushed over with a
coat of weak size and water.
Wenow come to gilding upon paint. The
grounds for gilding upon in these cases are
sometimes dead, i.e., without gloss, and some-
times with gloss, and polished, and varnished.
But whether the gilding has to be done
upon dead or gloss paint, it is essential that
the work should be got up as smooth as
possible. '’he smoother the surface to be
gilt the brighter will be the lustre of
the gold when finished. When the work to
be gilt is painted with flat or dead colour it
it will not require any parchment size as a
preparation ; but if the groundwork is a
gloss colour, a coating of egg-size will
be required, which is prepared as follows :—
Make a small hole in each end of an egg,
and blow with the mouth at one end, which,
if done carefully, will blow out the white of
the egg through the other, and into a pint
7
