Polythene on-ground layer
Ground vapour barriers (commonly known as GVB) are an effective and low cost retrofit option for addressing what can be the largest source of moisture entering the home from outside. Ground moisture barriers should be installed (regardless of existing subfloor vents are present) as most homes are still likely to experience a benefit.
High grade polythene is laid under suitable/applicable homes to ensure the minimisation of risng damp. Additionally, where installed, if water does enter the underfloor area it must be able to escape through gravity.
Ground Vapour Barrier is black. Ground Vapour Barrier needs to be installed correctly and in line with NZS:4246. Specific details include taping around piles and lapping.
Where can it be used?
Ground Vapour Barrier should be installed in underfloors where;