Frequently Asked Questions for a Better Understanding of Below-Slab Vapour Barriers
Polyethylene builder's film is an instrumental tool in the construction industry. It helps you keep out unwanted moisture when the concrete begins to cure. If too much moisture finds its way into a fresh slab at this stage, it will weaken the bonds between the concrete granules and the structural rebar used to support the building. With below-slab vapour barriers (polyethylene builder's film), you can ensure that moisture doesn't find its way into slabs and into the foundation over the course of the building's existence. The following discussion will help you gain insight on below-slab vapour barriers:
What is the Ideal Rating for a Vapour Barrier?
Basically, the rating on a below-slab vapour barrier shows the level of permeability of the film. It can be measured in terms of how much water the film will let through per millimetre, per day or per square metre. The unit of measure for permeability will vary among various film manufactures, but it will be denoted in Perms. When buying, make sure that you select a vapour barrier with a Perm rating that is equivalent to or below 0.01 Perms. Most of the materials with a rating considerably higher than 0.01 Perms are vapour retarders. They can mimic the performance of vapour barriers, but there is a high risk of moisture build up after some time.
Why Are Below-Slab Vapour Barriers Needed Yet There is Floor Cover?
Gases and moisture move by diffusion. This means that they can penetrate the small cavities and fissures within the concrete granules. Ground floors in contact with the foundation and soil pose a higher risk of contaminating your indoor air by letting in moisture and gasses trapped within the soil. Therefore, below-slab protection against moisture and other gaseous substances is necessary for keeping the intrusive gases and moisture at bay. Ordinary floor cover won't suffice!
What are some of the Attributes of a Good Vapour Barrier?
Besides low permeability, there are other attributes that you need to look out for when buying a vapour barrier. First, the film should be durable and non-biodegradable. In this way, it won't decompose despite coming into contact with moisture or being subjected to immense pressure. Secondly, look out for the "puncture resistant" label to ensure that the film won't tear apart during and after installation. Lastly, ask the vendor to show you a standardisation mark indicating that the product has been tested by relevant construction authorities and proven fit for use as a vapour barrier.
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