The industry is filled with many different types of underlayment made for different types of flooring and installation methods. In Toronto, most condos will have an IIC (impact insulation rating) rating specified already which will need to be used under the floor.
This will help from noise transferring down to your neighbors. Generally speaking with floating installations, the underlayment will be made of either a foam base material or it could be rubber or even felt. It will entirely depend on what the property managers have decided for the building.
If you were doing a glue down installation you will still require an underlayment, this underlayment is traditionally glued down to the concrete and then the engineered hardwood gets glued down to the underlayment. This is called a double glue down installation, the underlayment in this case can be made out of either a cork underlayment or rubber.
The thickness will depend on what the specified rating is from the property managers.
Have a question for the Toronto Flooring Solutions Team?
Feel free to contact them today!