Civil Engineering Reference
In-Depth Information
vertically perforated, sand or grog
faced, shades from white through red
to blue-black (Figure 2.3) - far too
numerous to provide a complete
listing here, let alone a description
of properties.
the southern brick of some 10 mm
less. Since the UK adopted the metric
system, it will be found that the
metric brick when used for
replacement purposes needs wider
joints than its predecessors.
Patterns of bonding have been
developed over long periods of time.
The early English bonds, in use
from around 1430, consisted of
alternate courses of stretchers and
headers. Flemish bond, which
consists of alternate stretchers and
headers in the same course, was
introduced into England in Stuart
times (Figure 2.5). There are of
course many variants of these bonds
- doubles and singles, cross bond,
garden wall bond, Sussex bond,
monk bond etc. They mainly
involve slight displacements of
alternate courses, or doubling or
tripling of headers, but all with the
proviso that there should be no
continuous vertical joints, or at least
kept to a minimum.
It is sometimes considered that
English bond gives a stronger wall
than Flemish bond, but there is little
scientific backing for this view. Of
far greater significance is the effect
of the mortar in the joints, and the
presence of voids - in particular the
Brick bonds
Bricks are bonded together in order
to form a monolithic wall without
serious continuous vertical joints.
In order to bond successfully in a
one brick wall, and so that the
bricklayer can produce a wall with
reasonably fair faces on both sides,
the length of the solid brick used as a
header needs to be twice its width
plus one mortar joint (Figure 2.4).
This rule is less critical with walls
thicker than one brick, for differences
can be taken up by varying the cross
joint. It was also not necessarily
rigidly applied with old bricks.
The actual size of the brick used
in existing walls is not crucial until
the time comes to cut out and replace
bricks which have deteriorated, when
there may be problems. In England,
Tudor bricks tended to be around
58-60 mm
thick and laid with thick mortar
joints, whereas in later times, rather
thicker bricks were used, laid with
relatively thin joints, although size is
not invariably a reliable guide to
date. Between 1784 and 1803 a tax on
bricks led to an increase in size, for
large bricks paid the same duty
as small
(13)
. Until the size of bricks
was standardised in the 1950s, there
were two common thicknesses in the
UK, the so-called northern brick
averaging around 70-75 mm and
Figure 2.3
A Warwickshire flour mill in locally made
loadbearing blue engineering brickwork,
sadly now demolished
The length of a brick
equals two half bricks
plus one joint
Figure 2.4
The size criterion to ensure bond. English
bond is shown
Figure 2.6
Diaper pattern formed by harder burnt
headers
Figure 2.5
Flemish bond
