Civil Engineering Reference
In-Depth Information
lack of filling of bed joints, and also
to a lesser extent, of perpends - and
the laying of pressed bricks with their
frogs facing down.
Some buildings with solid one
brick external walls were built with
the headers in a better quality or
harder fired brick than the
stretchers, giving a diaper appearance
to the finished wall. This was done
partly because it was thought, with
some justification, that the lightly
burnt through header provided an
easier path for rainwater to penetrate
the wall than the path interrupted by
the transverse mortar joint between
the stretchers, and partly for the
decorative effect of the harder burnt
or sometimes blue headers (Figure
2.6 on page 79). In any event, the
weathertightness of the wall depends
heavily on the condition of the mortar
joints.
BRE investigators on site have
occasionally found a wall built in two
leaves in brick on edge, known as
'rat-trap bond' (Figure 2.7) Such
walls are perfectly adequate
structurally for two storey
construction provided there are no
obvious defects. They are perfect
havens for vermin, however, which is
how the bond gets its name.
Reinforced brickwork
Can take several different forms,
with reinforcing bars threaded
through vertical perforations in the
bricks or blocks, fitted into gaps
created by a special bonding pattern
(eg quetta-bond), embedded in a
grout occupying a cavity between two
walls, embedded in concrete cast into
pockets formed in the masonry, or
simply laid in the horizontal joints to
enable
brickwork to span openings with
minimal lintel support (Figure 2.8).
Design practice is analogous to
reinforced concrete and most forms
can be created if required, including
beams, columns, slabs, retaining
walls etc. Hoop iron strips may be
encountered in older work.
Figure 2.7
Rat-trap bond
Bars either bonded in with mortar as the brickwork is raised or gr
con
Bars either bonded in with mortar as the brickwork
is raised or grouted in with concrete with lifts
Shuttered, then filled with concrete to bond in
the reinforcement
Ties at 5 per m
2
Consists of two longitudinal bars with welded-on connecting cross wires.
The overall height must fit into the mortar bed
Vertical or horizontal or both reinforcing bars
The reinforcement must be lapped at
corners and joints
Concrete grouted cavity. Width 2 x cover + bar
Figure 2.8
The more common forms of reinforced brickwork
