Stone facing attachment on ICF wall
SeanBWarm
| Posted in Energy Efficiency and Durability on
What is the best way to affix natural stone to an ICF wall? We have designed a walk-out basement home with ICF on the lower level and are planning to to use granite ruble stone from the property to face the walls over the above grade ICF portion. The detail drawings from this site show an air space behind the facing, but that detail was for a stick wall. If we were to use an air void behind the wall how would we anchor it given the significant weight and irregular shape of the stones?
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Replies
Dean,
Here are links to two brands of ICF masonry anchors:
TieKey ICF Masonry Anchor
Blok-Lok ICF Masonry Anchor
Thanks for the links Martin. So then, you're recommending the air space behind the stones, right? But help me understand... if direct contact with the ICF wall works below grade, why does direct contact with the stone facing not work? What is the downside to directly affixing the stone? I ask because I had hoped to apply the facing myself over a scratch coat. The air space/anchor method seems more technical. If I have to bring in a mason, I'm sure it will up my costs.
Sean,
Q. "If direct contact with the ICF wall works below grade, why does direct contact with the stone facing not work?"
A. Good question. I invite GBA readers who have built ICF homes to comment. My guess is that an ICF wall, with two layers of EPS, won't be adversely affected by the installation of stone without an air space. Where it gets tricky is at the windows.
I would include the air space if this were my home, because the air space facilitates window flashing.
Sean, what did you end up doing?
I appreciate your comments Martin, particularly with mention of the window flashing. We were thinking about taking our stone wainscotting over the ICF just above the bottom of the tallest windows, but now I think we should keep it below for this reason.
This article from JLC suggests roughing up the foam just a little (like with a stiff broom) with no need for fasteners, anchors, mesh, lath, or air space/rainscreen.
https://www.jlconline.com/how-to/exteriors/installing-manufactured-stone-over-icfs_o
Dustin, here are a couple of articles that might help:
https://www.finehomebuilding.com/2016/11/01/prepping-walkout-wall-cultured-stone
https://www.finehomebuilding.com/2016/12/05/students-master-cultured-stone-installation
Affixing the stone to wall depends on the type of stonework being done. If the stone veneer shelf is relatively deep - say a 9" average - and especially if the stone is relatively flat and not a round cobble-type stone the wall will be self supporting to the the extent that brick ties screwed into the icf plastic ties will be all that's needed. Check the icf manufacturer for screw recommendations. If you're appling a thin veneer that won't be "stacked" you'll be better off installing a continuous diamond lath that you can parge the mortar onto for adhesion to the wall. Either way you need to install weeps that will help water that could get behind the stone veneer makes its way out. Is this diy or are you hiring a mason?
We have done both natural stone and veneer stone on our ICF. The natural stone was done by including a ledge in the ICF which supported the vertical load, and nothing over the styrofoam of the ICF; both inside the house (20' tall stone fireplace) and outside.
We are also installing some stone veneer outside the house. I installed a layer of #30 asphalt paper, followed by a layer of Mortairvent screwed into the embedded strips in the ICF, then typical veneer system of scratch coat over screen (screwed into same strips) and then stone veneer. Overkill? Maybe, but its my house so I can do what I like to feel good about it!