Drywall – What wall material should be used behind the Kerdi system in a tub/shower


I know from my previous question that in most cases a cement board of some kind needs to be used. However, when the Kerdi membrane system is being used behind the tile, is it still necessary to use a cement backer board?

Best Answer

Schluter says that behind the Kerdi membrane a solid backing needs to be used. They define a solid backing as :

  • gypsum wallboard
  • cementitious backer unit
  • fibercement underlayment
  • fiber-reinforced water-resistant
  • backerboard/underlayment
  • coated glass mat water-resistant gypsum
  • backerboard
  • portland cement mortar bed
  • concrete
  • masonry

Found this in their Shower System Installation Handbook here. Link : http://www.schluter.com/media/ShowerHandbook.pdf