What are the most common causes of leaky homes?

The most common causes of leaky home are generally issues with cladding, roofing, decking or joinery.


  • Solid plaster is a rigid cladding and where this is fixed directly onto a timber framed building, the framing will flex, shrink and expand, causing the plaster to crack.
  • Where the exterior plaster does not have control joints, there is no allowance for a certain amount of ground movement, ground expansion in cold conditions or contraction in hot conditions.
  • Where there are cracks in the plastered cladding or sheet joins.
  • Where there are poor flashing details around doors, windows, pipes, wires or other penetrations.
  • Where exterior cladding has been poorly maintained (i.e. painting and sealing).
  • Where the cladding finishes on to the ground or paving, or is too close to the ground, allowing moisture to track or wick up behind the cladding and into the wall framing.
  • Poor flashing details or no flashings to horizontal joints.
  • Where a capillary gap has not been allowed for between the foundation and the bottom edge of the cladding to prevent wicking.


  • Where there are flat roofs with poor flashing details, poor gutter details, internal roof gutters, poor overflow outlets or no overflow outlets.
  • Where there are parapet wall details in the roof area without metal cap flashings or poor flashing details.
  • Where there are no eaves overhangs or very small eaves overhangs which give little or no protection to the exterior cladding.
  • Where there are poor flashing details around penetrations through the roof.


  • Where cantilevered deck joists penetrate out through the exterior cladding of the house, therefore compromising the exterior cladding. This is particularly bad where the decking above is permeable (i.e. timber decking or deck joists).
  • Where there is waterproofing membrane on top of decks which has been poorly installed; or where there are tiles fixed directly on top of the waterproofing membrane which may compromise the integrity of this membrane. NOTE: this practice is now generally discouraged by local authorities, and some types of membrane can no longer be used in these situations.
  • Where decks are built over living areas, effectively forming a roof over a living area. These decks are a common cause of water ingress.
  • Where solid handrails have poor or no top cap flashings. Plastered handrail caps are a poor detail.
  • Poor flashing details where the solid handrail finishes up to the exterior of the house.
  • Where the level of the deck is too high in relation to the finished floor level of the house. This makes it difficult to flash, and may also allow water ingress if the deck floods.
  • Where poor rainwater outlet details, inadequate fall on the deck to the outlets, poor or no overflow outlets installed, rainwater will build up and possibly flood back into the house in the event of the main rainwater outlets being blocked up.


  • Aluminium joinery can be a contributing factor in leaky homes. There is a major overhaul occurring in regards to the design and assembly of aluminium joinery.
  • Older type aluminium joinery lacked condensation channels, had inadequate drainage holes, poor back flashing details, and were very reliant on silicone sealant or the mitred joints for waterproofing.
  • Aluminium joinery has been modified and improved over the years and is still a work in progress.