Can I apply Earthaus Plaster to Cement Board or Mag Board?Updated a month ago

When applying Earthaus Plasters to cement backer board (such as HardieBacker or Durock) or magnesium oxide (MgO) board, proper surface preparation is important. The board must be finished to a level 4 drywall standard using normal drywall finishing techniques. Once dry and smooth, the entire surface should be primed with a water-based primer—either PVA or latex—with Earthaus Primer Grit mixed in to improve mechanical adhesion.

It's important to note that while these substrates are often used in high-humidity or wet environments, no Earthaus products are approved for use in wet areas such as shower stalls or tub surrounds with the sole exception of our Tadelakt System. For all other plaster systems, these substrates should only be used in dry, interior environments with proper surface preparation as outlined above.