Some claddings are more prone to causing leaky building problems. We look at the claddings most at risk and how they are applied to the house.
The types of cladding that have been identified as most commonly involved in leaky building claims are those with a plaster type finish with an applied waterproof coating. These are commonly known as monolithic claddings.
Specifically these cladding types are:
- EIFS (Exterior Insulation and Finish Systems).
- texture coated fibre-cement.
Many weathertightness problems have been caused by poor understanding of the materials used. This has resulted in poor design and detailing and poor application by inexperienced applicators.
Many leaky home designs imitate Mediterranean style houses, giving the appearance of solid materials such as concrete or plastered masonry. Many details common in solid construction have been copied, such as solid balustrades with a handrail attached, parapets or recessed windows. With lighter weight claddings attached directly to timber framing, extra care needs to be taken during detailing and construction.
Poorly designed or constructed details allow water to enter, and the waterproof coating then traps this moisture. The waterproof coating prevents water from draining or drying, and when this water saturates untreated timber framing, rapid decay results.
For more information on specific problems to look out for see What should I look for?
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 July 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.
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.
Texture coated fibre-cement
Texture coated fibre-cement consists of specially manufactured fibre-cement sheets fixed 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. Up until July 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.