In this article I'll cover some best practices for adhering our Thin Floor Warming Cables & Mats to an existing concrete floor.

• First you'll have to sweep and mop the floor to remove any dust, grime and oil.
• If you are laying mats down, you'll want to dry fit them first.  That means unrolling them, cutting the netting to flip them and making sure that they fit the way you 'd like them to.  Once you are satisfied, roll them back up again.
• Purchase some general purpose latex concrete admixture or primer as well as a can of spray-on adhesive contact cement and a roll of aluminum tape from your local building supply or concrete products wholesaler.  
• Roll on the primer to seal the floor.  It shouldn't have to be diluted over concrete but read the instructions to make sure.  Allow it to dry completely before proceeding.
• Un-roll the pre-cut mats or start laying cable.  The mats have an adhesive backing which should stick nicely to the primed concrete.  For Thin cables, use the aluminum tape to surround the cable and it should also stick very nicely to the primed concrete.
• For areas where tape or adhesive backing don't stick well on their own, spray the desired area with the contact cement and allow to dry for a minute before taping cables or sticking mat backing down.
• Use the spray-on contact cement under areas where cold leads and sensors will be going, allow to dry and then use the aluminum tape to secure the wires tight to the floor.
• If you are using mats it is recommended that you try to lay all or most of them with mat fabric facing up to keep the wire loops down.  Once the mats are down you can use Tuck tape to tape the edges of adjacent runs together so they act as a cohesive surface.  This makes it much easier to cover them with self-leveling cement or mortar since they will be weighed-down - preventing them from floating up.
• Note that a cold chisel and hammer may be required to chisel out grooves for the cold leads if you are tying to use less than 1/4" of self-leveler or thinset over the cables.
• If your installation will need to be inspected by the local electrical authority before cement can be applied it is recommended that you not waste much time trying to get all the loops or corners down with tape since the tape tends to come up after a day or two.  You are better off doing this just prior to cement work.

Anyway, hope this advice helps!