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:
- NZS 3604:2011 Timber-framed buildings section 6.14 Prevention of dampness
- BRANZ Good Repair Guide: Damp Subfloors