Final answer:
The proper primer for heat welding a vapour barrier to a concrete deck is usually specified by the vapour barrier's manufacturer and can vary depending on the material, commonly being asphalt-based or epoxy-based.
Step-by-step explanation:
When heat welding a vapour barrier to a concrete deck, it is crucial to use a primer that is compatible with both the vapour barrier material and the concrete surface. The purpose of the primer is to enhance the bond between the barrier and the deck, ensuring a secure and durable seal. Typically, manufacturers of vapour barriers will specify which type of primer is most suitable for their product. This recommendation should be followed closely to avoid adhesion failure.
In many cases, the primer will be an asphalt-based or an epoxy-based product designed for use with the specific type of vapour barrier being installed. For example, PVC or TPO membranes often require specialized primers. It is also important to prepare the concrete surface properly before applying the primer to ensure good adhesion; this usually involves cleaning and possibly etching the concrete to remove any contaminants or loose particles.