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. (CB)
Poorly designed or constructed details
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. (CB)
With no cavity between the cladding and the timber frame that would
allow for drainage and ventilation of moisture at the base of the wall, houses
built up to 2004/2005 with monolithic cladding are at a very high risk
of rotting inside their shell. (See
also: Constructing Cavities for Wall Claddings).
Simpler is safer
Complicated building designs exacerbate the problem. Complicated designs
are defined as having many cladding junctions, or junctions between
the cladding and roof planes or other materials. Windows are
also likely to be complex shapes and sizes.
Decks are also a major cause of leaks. For timber-slatted decks
problems have often occurred where the deck is attached to the house or where
cantilevered joists have been used. Cantilevered joists are continuous from the
inside of the building, out through the cladding to the outside of the building
and are very difficult to seal where they penetrate the cladding. (CB)
Design
features of a high-risk home are explained in detail, in an
interactive drawing, on the Prendos' website. (Clicking on a number in the
drawing or table opens up a new window with pictures of each respective
defect/damage).
Another interesting table is on the Website
of the Department of Building and Housing, listing Common Areas of
Weathertightness Risks, as outlined in the drawing below, and ranking them by
incidence (in %).