Architects memo no.
59: August 1999
kiwi castles - or monolithic monsters?
The solid monolithic appearance of concrete or plastered masonry
structures is much valued in the current New Zealand building climate.
The cost of such building methods can, however, be a deterrent and there
are many innovative methods available to mimic the desired appearance
at a lower cost.
One method uses fibre-reinforced cement sheeting fixed over traditional
timber framing. The monolithic appearance is crucially dependent on
the use of field applied flush jointing systems. Such systems have the
potential to produce durable structures with excellent aesthetic appearance.
The systems demand good building disciplines to ensure a successful
outcome, and the leading suppliers of the sheeting provide excellent
technical literature and guidance.
Critical to the success of the system, is the use of kiln-dried timber
for framing and floor joints; accuracy in the design and alignment of
the framing; correct laying out of the sheets, especially around openings;
the number and placement of the fixings; and the provision for the correct
type and number of relief and control joints. There are also several
details such as sills, jambs, drip edges etc. that need to be correctly
fitted for long term performance.
The contractor who applies the joint filling and texture coating also
has a major role to play, as these elements are obviously an integral
part of the weatherproofing of the structure.
There are clear areas where the applicator should accept responsibility.
These are: the use of trained staff and approved materials; the use
of anti-corrosive primers over the fixings and other metal elements;
the level of texture used to achieve the desired finish; and the use
of colours which comply with the sheet manufacturer's specifications.
However, there is a grey area, which is of concern!
Typically, when an applicator starts painting a surface, he or she
accepts the responsibility that the surface is fit for painting. With
such structures as we have described, however, it is unreasonable to
expect that the painter/applicator is so skilled in the building trade
as to recognise whether any of the above mentioned crucial steps have
been correctly carried out.
If water enters the structure, or a joint fails, the coating applicator
is often the first in the firing line. Proving that the fault is one
of construction can often be difficult and time-consuming. Furthermore,
some mud always sticks.
This memo does not purport to have an answer; it simply raises the
problem of interdependent building elements, the difficulty this raises
of responsibility for breakdowns; the need for inspection services,
and the question of who pays for them? It also presents a strong case
for both the supervision of the contract and the appointment of preferred
or nominated contractors.
Does anyone remember the 'Clerk of Works'? Come back friends - all