The subfloor in my home is 4" planks. The previous owner removed the hardwood, painted the flooring and left it that way (I have no idea why you would do that).

Regardless I want to put down tile. Do I need a moisture barrier between the mortar and the flooring?

FYI, I have to use mortar. Adhesive isn't an option because I'm going to be using electric radiant heat.

  • What system are you using for the radiant heat? Does it not have some integrated isolation or moisture blocking layer? – JPhi1618 Dec 4 '19 at 21:25
  • I haven’t purchased one yet but all of the systems I have looked are both designed and required to be encased in mortar. – mreff555 Dec 4 '19 at 21:30
  • I would think you will need a layer of cement board on top of the sub floor first! – Kris Dec 4 '19 at 23:50
  • That makes sense. Would 1/4 be thick enough? – mreff555 Dec 4 '19 at 23:56
  • Since the floor is a single layer now I would put a layer of felt down and bed the heat wires then a thin backer board set with thinset as you don’t want to screw into your heat cables. I have done this type of floor several time and have found using wood screws close to the heat cable but leave the head at slightly higher than the cable then when you bed the cable the screw heads hold the bed solid and provide a guide for height . It takes some extra work but locks the base to the flooring. – Ed Beal Dec 5 '19 at 16:00

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