[Lump]

Derek, you are not going to hurt the tuff form pan nor the thinset with the heat cable.

Question is will the liquid waterproofer hold up? Typically Mapegum is sold with the tuff form system.

If the liquid waterproofer is suitable over the heat I would scuff the tuff form pan first, hot glue the wires in place, skim coat with a premium modified thinset, apply waterproofer according to manufacturers instructions then set the tile.

Best place to check is with the waterproofing manufacturer.


Remember with the system that you are dealing with you likely have 4 different manufacturers.
1) tuff form
2) water proofing
3) thinset
4) heat cable

You are the one holding the bag if things go bad.....a salesman will tell you anything.

Be sure to get it in writing, maybe in email.