Remedies: moisture

Bungalows have generally coped well with moisture because of their wide eaves and weatherboard construction.


Bungalows may leak in extreme weather conditions (such as horizontal driving rain) but the wide eaves typical of the bungalow means that they are generally quite well protected and weathertightness is not a major problem. Look for problems around bay windows and the flat roofs above them.

Once insulation is added and spaces are hard lined, the house becomes more airtight so one aspect that must be addressed during renovation work is how the principles of E2/AS1 can be incorporated into the reconstruction.

Issues to consider include:

  • the detailing of windows where the existing window has been removed or a new window is to be inserted into an existing wall
  • minimum roof pitches on lean-to construction – many are below the current minimum slope requirements
  • the lack of a wall and roof underlay (see roofing and cladding for solutions)
  • the need for a cavity when matching existing – see regulation and compliance, which details a path that may allow the cladding to be installed without a cavity provided it matches that existing. 

Window flashings

Traditional window and other head flashings have simply been inserted into the lap or joint of the weatherboard immediately above the opening. As long as the flashing remains in good condition, the detail appears to have generally worked well at protecting the top of the window. Modern details that require the flashing to be lapped under the wall underlay cannot be applied to an existing bungalow wall unless the cladding is being removed. 

BRANZ also believes that, where a window matching existing is being inserted into an existing wall, using the same detail is a logical solution. 

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Internal moisture

Draughty houses are less prone to internal moisture problems than newer, more airtight houses because of the air that moves through gaps around windows and doors, through chimneys and even floorboards. 

As a house becomes more airtight, generally as a result of hard lining, internal moisture generated from cooking, washing and unflued gas heaters and clothes dryers, can become a problem. 

If there is a musty smell, it may be able to be traced to:

  • a damp subfloor and the migration of the moisture through a draughty floor 
  • a leak from an internal gutter or through the roof or wall cladding.

One solution to a damp subfloor is to lay 0.25 mm polythene sheeting to completely cover the ground under the house. Ensure that the ground is shaped so no water accumulates on top of the polythene. Polythene sheets should be lapped a minimum of 150 mm, preferably taped, and tightly butted up to foundation walls and piles. Weigh down the sheets with bricks or concrete to avoid them being displaced by air movement from subfloor ventilation.

Renovation work will generally make the bungalow more airtight. Design solutions must include systems to remove moisture such as:

  • installing extract fans in the kitchen and bathroom that are ducted to outside
  • installing insulation where possible to keep indoor temperatures higher
  • installing security catches to windows that can be opened to allow ventilation without providing a security risk (but try to avoid siting on window sills)
  • if installing new windows, ensuring they have trickle ventilators to provide continuous ventilation.

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Other problems

Rising damp

Moisture being drawn up through brickwork can be a problem with chimneys. See Common problems and remedies: Brickwork for more.

Subfloor moisture

See Insufficient subfloor ventilation.


See Common problems and remedies: Roofing and cladding.


Rot is common when moisture is present, and can cause significant structural damage. Read more.


Mould is common when moisture is present, and can be harmful to health. Read more.