In the 1990s certain architectural designs and finishing systems became
very popular in New Zealand: “Mediterranean” style homes, some with
complex structures of the building envelope, most with a plastered or stucco
type of finishing.
Certain cladding systems are now known to be risk factors, especially
when poorly detailed or finished. The
most risky are:
Texture coated fibre-cement
Texture coated fibre-cement consists of specially manufactured fibre-cement
sheetsfixed to timber framing, with the joints reinforced and
flush-stopped with proprietary fillers. It is then coated with a texture
coating. The texture coatings may form the waterproof coating, or an
additional waterproof coating may be applied. Until 2004, the fibre-cement
was always fixed directly to the timber framing. Texture coated
fibre-cement relies on the waterproof coating to keep moisture out and this
coating must be maintained. (CB)
Cement stucco
Stucco is a solid cement plaster (19-20mm thick), reinforced with
galvanised wire netting or expanded mesh and supported on fibre-cement, plywood
or heavyweight building paper. Where the stucco is applied over a non-rigid
backing (building paper), it should incorporate a cavity behind the building
paper. Up to 2004 most stucco applications over fibre-cement or plywood were
allowed to be attached directly to the timber framing.
Stucco should not be confused with texture coated fibre-cement. The backing
fibre-cement sheet for stucco is different from that used for texture coating.
Also the plaster coating on stucco is a cement plaster mix, applied in two or
three coats, up to a thickness of approximately 20mm. It is then painted to
ensure it is waterproof. (CB)
EIFS cladding systems
EIFS (External Insulation and Finish System) is a cladding system using 40 or
60mm thick polystyrene boards, plastered with a 3-5mm cement-based basecoat
and then painted with a waterproof coating. The cement plaster has polymer
modifiers added that make it more flexible and allow a thinner
coating to be applied. The base coat - one or two may be applied -
is reinforced with alkali-resistant glass-fibre mesh.
EIFS was traditionally constructed by fixing the polystyrene directly to the
timber framing. Several proprietary systems are available, but some installations
have not followed a proprietary system. They lacked the specially
manufactured flashings required, mixed brands of plaster and paint or
have been fixed without following the manufacturer’s instructions. (CB)