Help!!! Stone veneer type s mortar failure
 

Hi, I'm an experienced DIYer, I've done many remodels and built my own home. However, I just had a failure on a project and I can't seem to figure out what I'm doing wrong.

I have a zero-clearance gas fireplace and I built a surround for it out of hardi backer board and metal studs. I have a stream on the property, so I've been gathering flat stones to do a veneer of native stones.

I've tried three times to mortar the stones to the backer board using type S mortar, and every time the mortar failed to adhere to either the stones or the backer board. I've used dry morter, wet mortar, I've made the stones and the boards wet, and dry. I can't figure out what I'm doing wrong.

Any help/ideas are appreciated!

Sounds like the stones are too heavy & smooth for the amount of surface area available for adhesion on the backside. Personally I wouldn't have chosen tile backer board either. Can you post a picture of the stones you're trying to adhere?

A smooth surface trying to grab onto another hard none poris smooth surface.
I would have used plywood with tar paper over it then wire mesh instead of tile board.
The mesh is sold in Lowes and Home Depot in the masonery area.
If there's no flat spot on the back side of the stones it still might not hold.
That's why faux stones would have worked out better.

activa

Hardi isn't suitable for Type S to bond to without some additional help. If you will switch to modified tile thinset mortar you'll do fine. You don't need tar paper and mesh and all that crap if you use thinset.

You will have to stack the stones on spacers probably until the thinset dries then you can remove the spacers.

Ayuh,... That sounds like it might work,...

Scoring the backsides of the stones with a grinder might help as well...
I might resort to duct tape to help the spacers to hold things til it sets...:laughing: