Civil Engineering Reference
In-Depth Information
Workmanship
Workmanship is particularly
important in construction of the outer
leaf of a cavity wall, so as to reduce
the quantity of water passing into the
cavity, and in keeping the cavity clear
of obstructions and other faults which
can lead water across. If cavity
insulation is to be used, good
workmanship is also important for
installation of the insulant, either
during construction (for built-in
board or batt materials) or after
construction (for blown-in or injected
fills)
(112)
.
Inspection
All external walls should be inspected in
detail and cracks noted. If these are more
than a hairline, crack widths will need to be
recorded and long term monitoring
considered (Figure 2.35). If visual evidence
of distress is found then a full plumbline
survey may need to be undertaken. Also,
walls might have been built 'out of true'. A
metal detector may be used to locate wall
ties if inadequate numbers or incorrect
distribution are suspected.
Any potentially overstressed narrow
piers should be identified, and the wall
above each opening examined both
internally and externally for signs of stress.
Lintels may need to be exposed to
establish material, shape, size, condition
and width.
See also the same section in Chapter 2.1.
In addition to those listed in Chapter 2.1,
the problems to look for are:
◊
inadequately protected or missing ties
Figure 2.35
Cracking due to proximity of trees on a
shrinkable clay site
◊
ties sloping the wrong way
◊
inadequately embedded of ties
◊
cracking and instability due to corrosion
or absence of wall ties
◊
mortar on ties
◊
reduced weathertightness due to
induced cracking
◊
cavities too narrow
cavities fill bridged
◊
◊
damp penetrating to the inner leaf -
cavity trays omitted or poorly detailed
◊
cavity fill deteriorated
◊
thermal bridging and condensation
◊
stop ends omitted
◊
corrosion of inadequately protected or
damaged steel lintels
◊
rotation of concrete boot lintels
◊
weep holes absent or blocked
◊
presence of corroding hoop irons
