Preventing dampness under suspended floors

For suspended floors that are damp because of moist ground conditions and/or lack of adequate ventilation, installing a sheet polythene vapour barrier over the ground to minimise the amount of water being emitted into the subfloor space is recommended.

When installing the ground cover:

  • remove any sharp object that might puncture the vapour barrier before laying it out
  • lap joints 150 mm
  • ensure that it fully covers the soil area under the building and prevents water ponding on top of it
  • weigh it down with stones or old bricks to stop it moving in the wind
  • trim and tape the vapour barrier around piles.

Also check that:

  • as much ventilation as possible has been provided
  • there are no plumbing or drainage leaks
  • surface water is not able to flow under the house.

Find out more

Resources available include:

Buy NZS 3604:2011

Published in building.