I have an exisitng concrete slab on grade that i installed a 1/8" cork underlayment and then electric radiant heating mats on top of that.

The mats do not go wall to wall, however, i want to tile wall to wall.

On top of this i want to install ceramic tile in thinset, however, the floor is not perfectly level not only becuase of the radiant heat mats but also there are a few small bumps in the cork.

I believe an expert floor tile layer could float the floor, but i am not an expert.

Can i install a 3/8" layer of floor leveling compound over the cork and radiant heating and then do the tile with thinset?

 

Why are you using cork?

I would:

1. Remove cork
2. Install heating mats directly to slab
3. SLC
4. Ditra
5. Tile

 

The cork is recommended by TCNA and the radiant flooring provider. I need a thermal break from the concrete to the radiant mats.

 

I would not recommend cork for one main reason: moisture. If the cork gets wet from moisture, leak, etc, it will could swell and crack your tile. Also, if you were to have the cork as a underlayment, you need to use epoxy grout.

There are much better products out there instead of cork, Wedi is one of them that provides a barrier, along with Nobleseal, etc.

We not hear of many people installing cork as a underlayment for tile. I just think it's the best approach.