When using the cork underlayment over concrete slabs for insulation purposes it it necessary to fasten the cork to the concrete? If so, What do you use to fasten it with? Also can a person install the radiant floor heat under a vanity. I have a 18×18 vanity and it is just easier to take it out before I start to install ceramic tile.

I would definitely recommend adhering the cork to the concrete with a thin layer of modified thinset cement (the same cement you are going to encase your heating system in). If the cork was not secured to the sub floor the thinset would pull it up while it was curing, and as you can imagine, this would create all sorts of problems for final floor.

I would suggest not heating under a vanity if the vanity is going to sit directly on the finished floor. As our system warms, heat is going to build up underneath the vanity and can potentially lead to over-heating issues. If you absolutely have to heat under the vanity, I would recommend installing a vent or something at the base – allowing any heat building up a place to dissipate.

If you have any other questions, don’t hesitate to contact me again!

Seth