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 is forgiven.
The Resene architect's memo section provides technical information on a variety of topics relating to paints, finishes and coatings.
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