Easy ways to ventilate and reduce damp

  • Air your home regularly. Open doors and windows for 10-15 minutes each morning, or use a ventilation system. Airing out a room when you turn off the heater also helps to avoid condensation.
  • Use energy efficient, low emissions heaters. Heat every room being used by someone to at least 18°C. Don't use unflued or portable gas heaters.
  • Dry washing outside. Use a washing line or rack under a covered verandah, garage or carport. Use a clothes dryer only to finish them off, or if it's raining.
  • Use extractor fans and rangehoods. Make sure they're big enough to do the job, regularly cleaned and send air to the outside, not your ceiling space.
  • Turn on the bathroom fan before a shower or bath. Shut the door and open the window an inch. Afterwards, leave the fan running until the moisture clears.
  • Use lids on pots when you cook. This helps to stop the steam escaping.
  • Move furniture away from walls in winter. A 10cm gap will discourage mould (especially on external walls).
  • Leave wardrobes slightly open. A little air circulation discourages mould growing on fabric.
  • Use a dehumidifier on damp days. This will help to reduce condensation but it won't solve a dampness problem. It's better to tackle the sources of damp and heat and ventilate your home.

Checklist to find sources of damp and mould

  • Extractor fans, rangehood and clothes dryer are sending air and moisture to the outside, not inside or in the ceiling space. Extractor fans and rangehood filters are clean.
  • Extractor fans and ducting are at least 150mm diameter (smaller ones won’t be effective, except in a toilet) and ducting isn't damaged, and is short and as straight as possible.
  • Plumbing pipes and services have no leaks and no moisture is getting into walls, floors or near showers or baths — get under the house if you can.
  • Downpipes and gutters are clear and not leaking, and downpipes connect to storm water drains — check in the next downpour.
  • Subfloor wall vents are unblocked and the subfloor area is clear.
  • Wall and roof cladding, and flashings have no leaks.
  • Concrete walls and floors have no damp patches or white mineral deposits which indicate moisture is coming through (lift the flooring to check).

  • The little device that can help you find problem areas

    Use a hygrometer – a low-cost digital device you can buy online – to check room temperature and humidity over a few days (especially in winter). If the temperature is below 18˚C and the humidity regularly over 65%, the room is too damp to be healthy.

  • Need some healthy home advice?

    Get guidance to assess how warm, safe and dry your home is, and discover what you can do to improve it. You can do a healthy home check yourself online, or a certified advisor can visit and assess your home, and tailor an improvement plan. Many offer their services free of charge.

Things to fix, install and improve to combat dampness

  • Bathroom extractor fan — install a run-on timer switch to keep the fan running for a few minutes after you switch it off, or a humidity sensor to turn on the fan when it detects steam.
  • Install a shower dome — to stop steam escaping into your bathroom.
  • Buy a bed base — if your mattress is on the floor, a bed base will let air circulate underneath.
  • Improve drainage — if surface water flows under your house during heavy rain, reshape the outside levels or install drainage. Ask a licensed drain layer for advice.
  • Install subfloor vents — your house should have them on all sides. Ask a qualified builder for help on sizing and/or installation.
  • Seal damp concrete or masonry — use a waterproofing sealant or moisture barrier. Ask an expert about the best product for your situation.
  • Get moisture content professionally measured — hire a registered or accredited building surveyor to measure the moisture content of your home's materials (often the easiest way to find hidden leaks). Find an accredited building surveyor(external link)
  • Install a ground vapour barrier — thick polythene sheeting installed on the ground under your house keeps moisture in the ground and stops air under the floor from getting damp. How to install a ground vapour barrier(external link)