Hydro-static pressure or green concrete contributes to 85% of flooring failures, according to the Building Services Authority. The QBSA has countless claims of flooring failures each year, mostly due to moisture issues.
These could be avoided by completing a simple moisture test on your concrete. A majority of floors are never moisture tested, which is a very quick and easy test to complete.
To conform to the Australian standard (AS1884‐2012), concrete must have a reading of no greater than 75% relative humidity.
As a general rule of thumb, concrete will dry at approximately 20‐25mm per month in an average environment. That means that a slab of concrete 100mm thick can take 4‐5 months of drying time to conform to Australian Standards.
Concrete is like a sponge and will continue to absorb water if present. When exposed to rain, locked up in a building or has a curing agent applied, this will further increase the drying time. Higher elevations of relative humidity will slow drying times even further.
Hydro-static pressure comes from underneath the concrete and moves its way through the concrete via the capillary voids in the matrix of the concrete. It can come from things such as a hidden spring running underground, high water tables or low lying flood land.
Once a floor covering has been installed, it will draw any moisture to the surface and if there is no means of escape will react with, and break down the bond of the subsequent floor covering..
Waiting for the concrete to dry isn’t really an option due to the lengthy time delay. Concrete moisture barriers such as Moisture Proof should be applied to prevent any future issues.