couple questions about installing natural stone veneer

[Chase Golombek]

I have been tasked with installing NSV over an old brick fireplace. I could think of two options.

1. scratch coat brick, let dry, install stone.

2. install 1/4" CBU then adhere stone.

type s mortar?

any help would be much appreciated. thank you

[Davy]

Depending on your brick and if it's painted or not, the scratch coat may or may not stick to it. If the instructions say a scratch coat is recommended, I'd install lath using Tap-Con screws and apply scratch coat over it. I don't know if it's recommended but I've seen guys stick those stone directly to the lath.

[Davy]

A scratch coat isn't just a coat of mud but rather a rough coat. After you apply about 3/8-1/2 inch of mud over the lath, you scratch it using a rake. Home Depot has the hand held rake that creates the lines. Or, I've used a small piece of lath, say 5 inches square.

[cx]

That's a particularly nice lookin' scratch coat there, Davy.

Might this not be an application for that Laticrete 3701 Lite product we were recently discussing in this thread in the Hangout, Davy? This was one of the few applications I said in that thread that I saw for such a product.

[CaliGrown]

Scratch it as Davy suggests. Set the stone with a type s & thinset combo. Dampen your scratch coat, skim the back of the stone with thinset for a bond coat. Then butter it up with type s and set it into your scratch coat. Set a few pieces and beat them into satisfaction

[cx]

Sounds excessively complicated to me, Christopher. If you wanted to thinset the stones, why would you not just brown over your scratch for a flat, smooth substrate and then just thinset your stones?

[CaliGrown]

Natural veneer typically varies in thickness. The mortar sandwich lets you butter at varied mud bed depths, to set everything tight joint and flush with one another

[Chase Golombek]

Thank you for the replies.
I will go with the lathe and scratch coat. This brick is unpainted. The lower part of the fireplace is ceramic tile. Hopefully i can knock those off clean and adhere to the mortar behind it.

[Davy]

Kelly, I haven't ever used the 3701 lite but it would probably work fine for a scratch coat. I would want to make sure the mud sticks well to the brick if lath isn't used.

Not my work but I've seen those veneer type stones fall off the scratch coat when fat mud alone was used. Every piece didn't fall off but one here and there. And it did take a few years of freeze/ thaw weather but I was surprised to see it. I remember thinking that adding thinset to the mud would help it bond better.

[cx]

I've never had any confidence at all in the "systems" that use Type S mortar to install those manufactured stone veneers, 'specially outdoors.

Probably why Laticrete (first one I was aware of) and other tile installation product manufacturers developed their own installation systems for those products using waterproof membranes and thinset mortars.

I only mentioned that new pookie because it's advertised to be installed without metal lath. Indoor fireplace with raw brick seemed to be one of the few applications where I might trust such a product. At least 'till it's been on the market long enough to establish a track record one way or the other.

My opinion; worth price charged.

[ss3964spd]

I feel like I'm missing something.

If the brick is flat, clean, unsealed, and sound is there any reason he couldn't simply set that stone directly to the brick with thinset mortar?

To wit; natural slate directly to brick with Versabond.

[cx]

Originally Posted by Dan

If the brick is flat, clean, unsealed, and sound...

If those conditions existed and if tiles were large enough, I can't see a reason not to do that, Dan. But I think it would be the unicorn of brick façades that would qualify for such an installation without first flattening the surface.

My opinion; worth price charged.