Subscribe or Renew Membership Subscribe Renew

How to apply Stucco to this unique combination of substrates

lazukars's picture
I need to apply a 1/8" scratch layer of Stucco on Hardie Boad in a Shower.There's also some stainless steel brackets that support the shower shelves, which can be seen in the picture below. I plan on putting Weldcrete on those brackets to ensure the Stucco sticks to the stainless steel. 
 
Question:
 
Is it ok, to Stucco Directly onto the Hardie Board and Metal Brackets as described above? 
 
Backgound:
 
The reason for the scratch layer of Stucco, is that I'm installing Tadelak (https://en.wikipedia.org/wiki/Tadelakt) on all the shower walls. 
 
I've learned how to do this from an experience Tadelakt installer in Utah. He's been formally trained in Morocco and has years of experience applying Tadalakt.
 
To give you an idea of what Tadelakt looks like below is a pic of a completed Tadelakt accent wall in an upstairs bath that I've completed. The next wall I'm about to Tadelakt are walls in a Master Shower. If you're wondering, Tadelakt, is indeed waterproof, so it's ok in showers.
 
However, there are concerns. Tadelakt is a 50/50 combination of Lime-S and crushed marble, and the installation process is as follows. The Tadelakt is applied, in 4 thin layers to over a 1/8" base layer of Stucco. The base layer of Stucco is directly applied to Hardie Board. This is how I've Tadelakted two other walls, including the picture above. They've all held up well at this point.
 
The main concern or worry is that the base Stucco will detach from the Hardi and Stainless steel brackets over time due to the constant temperature and moisture in the shower. I've read that Stucco should be applied with metal or fiberglass lathe on Hardie. Some people mention using an Stucco Bonding adhesive on the Hardi as an alternative to the lathe. Both these methods ensure proper adhesion of the Stucco to the Hardi.