Thin stone veneer over rigid foam
Last Post 04 Mar 2012 09:13 AM by ICFcoatings. 33 Replies.
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methierUser is Offline
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29 Aug 2010 11:56 AM

Has anyone ever installed thin stone veneer (natural) over 2" XPS rigid foam ?

2x6 wall construction
1/2" plywood
tyvek or typar house wrap
Driwall rain screen 10mm
2" XPS foam
Metal lath
Scratch coat
Thin stone veneer

If so, how is the stone supported ? Due to the outwards projection caused by the foam, nails or screws to hold the metal lath is no longer sufficient.
What are the recommended solutions in this case ?

Bonus question...do I have the correct order of layers listed above ? ie: should the XPS be placed over the house wrap followed by the Driwall rainscreen, or as indicated above ?

Thanks

cmkavalaUser is Offline
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29 Aug 2010 01:44 PM
bear stone on footer ledge or steel angle bolted to foundation. I would not put rainsceen between plywood and foam, I would put between lath and foam or use paper backed lath
Chris Kavala
info@southernsips dot com
1-877-321-SIPS
FL. Lic # CBC036455, GA Lic. RLCO000624, LA Lic. # CL33845
methierUser is Offline
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29 Aug 2010 08:08 PM
Thanks Chris.
You've seen this done before ? I know that regular (full thickness) stone is meant to be stacked and held up by the foundation wall, but I wasn't sure that this could be done with the thin stone product. All the installation instructions that I've seen indicate that this product is meant to be glued onto a wall surface and supported by the wall.
And anybody that I've talked to so far is stumped about how to install it...
Bruce FreyUser is Offline
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01 Sep 2010 02:01 PM
What do you mean by thin?  Unless you are using stone tile (e.g., 12" x 12" x 3/8" thick) in a non-freezing climate where you can use adhesive, you need some mechanical fasteners. 

In commercial buildings, we think of "thin" stone as anything less than "cubic" which generally means less than 3" to 4" thick.  Stone cladding needs to deal with vertical (deadload) and horizontal (wind and/or seismic) loads.  Attachment is normally done with some type of patented fastener such as http://www.stoneclip.com/uni-strut.html using kerfs cut in the top and bottom of the stone pieces.  Each fastener usually serves as a dead load anchor for the piece above it and as a windload anchor for the piece below it.  Very large pieces may have intermediate windload anchors.  As you can imagine, the anchors need to be taken back to structure, so they will penetrate the insulation. 

Rainscreen facades usually have open joints (hence the name) without grout, sealant or mortar so the space should be directly behind the stone.  The air and water barriers usually go behind the insulation.  We prefer a minimum 1" (2" is common), but we also use this space to absorb structural erection tolerances which (hopefully) is less of a problem in single family project.

If the stone is thick enough (4 or so inches) to stack like bricks on a brick ledge or shelf angle, you just need brick tie type of anchorage and brick wall type detailing.

Bruce
methierUser is Offline
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01 Sep 2010 09:18 PM
Bruce, thanks for the link to the stone clip fastener. Looks interesting. It would require a lot of nails or screws, one per stone, and these would have to be long enough to go through the 2" XPS foam, the rain screen and the1/2" plywood. But since each stone is held seperately it looks strong enough.

The stone that we were looking at is available at Rona and I believe that it is less than 2" thick (between 1.5" and 2").
Product is called Ledgestone Decorative wall ceramic, Mono Serra Ceramique.
Link: http://www.rona.ca/shop/shop?storeId=10001&catalogId=10051&page=1&langId=-1&keywords=84665331

There are similar products from other stone suppliers in town, but my wife likes the colour/style of the one sold at Rona, and it is a bit cheaper as well.

Are you saying that you would recommend an additional "water barrier" product in addition to the house wrap and the rain screen ?
When you say "We prefer a minimum of 1", are you referring to the amount of insulation or air gap ? In the case of the thin stone application, I don't see how there could be an air gap, so were you talking about the regular 4" stone application ?

With the use of the stone clip fastener, would this completely change the way the stone is installed ? In other words, no need for metal lath and scratch coat ? Or is it basically the same installation but the clips are in addition ?

Martin
Bruce FreyUser is Offline
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02 Sep 2010 05:37 AM
Thanks for the link. That makes it clearer. I couldn't find out much about the product (Japanese company, product manufactured in China), but it looks as if it is made to be installed as a tile with adhesive. I doubt it is thick enough to kerf and the joints around the pieces would not look good.

I would do as Chris sugggested (he probably understood what you were thinking better than I) and have a brick ledge or shelf angle to carry the weight and use the adhesive to hold it to the wall. Your idea of doing a plaster/stucco wall finish and gluing cast stone to it is probably OK. My only concern is that if you are in cold climate, freeze/thaw could pop the tiles if water gets behind them.

Since you are essentially doing a plaster/stucco wall, it should be detailed like one, so Chris is correct in suggesting that the rainscreen/drainage plane should be between the foam and the lath.

FYI, on a commercial building with larger pieces of stone, our wall buildup would typically be:
1. Structrure (usually concrete or masonry)
2. water/air/vapor barrier
3. stone supports attached to structure
4. insulation (supports penetrate insulation)
5. 1"-2" air space
6. stone with open joints

note: for using kerfed stone in a cold climate, the kerf on the top of the stone must be filled with sealant as it is installed or freeze/thaw will break the kerf.

Bruce
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02 Sep 2010 09:16 AM
See http://www.buechelstone.com/PDF/NTVinstall.pdf for instructions on thin veneer installation. What you need to be sure about is the shear strength of the long screws holding the lath through the foam. You probably should consult an engineer to ensure the screws used will work properly.
JellyUser is Offline
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02 Sep 2010 08:03 PM
Just to clear things up, Martin, yes the normal installation is to press the thin stone veneer into a wet scratch coat. The only thing complicating that is the foam layer. Hence the suggestion for something extra for the stone to bear on.

How much veneer are you installing? is it like a 12 foot high wall, or just a foot or two down by the foundation?
methierUser is Offline
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03 Sep 2010 10:41 AM
The house will be located in Ottawa, Ontario, Canada...so very cold climate.
Here's a link to some snapshots from my Google Sketchup model which shows where the stone will be installed. The rest of the exterior will be stucco/EIFS. That's an entirely different problem
http://profile.imageshack.us/user/methier
In case the above link doesn't work, here's a direct link to the front and rear elevation pictures:
http://yfrog.com/n6frontelevationj
http://yfrog.com/03readelevationj
(Seperate topic, but I'm amazed at how easy and useful Google Sketchup is. Awesome tool for planning a new house)

I understand the general idea of having something extra (in addition to the scratch coat) to hold the stone. What I'm still struggling to understand is exatly how the stone is supported. Is it as simple as having the first row of stones sitting on the foundation wall and then build up from there ? My foundation wall can be made an extra 2" thicker to allow this. I had been told that relying on the screws holding the metal lath is a bad idea since they will sag in the long run since they are sticking so far out due to the foam.
Yes, I definitely intend on having this entire support system reviewed by an engineer. The designer/draftsman will consult an engineer, but I wanted to have a good idea of how this would work and if it had been done befoe.

Thanks for all the comments and suggestions so far,
Martin
BruceUser is Offline
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03 Sep 2010 01:05 PM
The lath is screwed to the wall. The scratch coat is put on and the stone is stuck to the scratch coat with modified thinset. The modified part of the mix basically makes it sticky so the stones will stay put when placed. What keeps everything from falling to the ground is the screws that attach the lath to the wall. Then you are counting on the scratch coat and modified thinset to keep the stones on the lath.

Does that answer your question?

What I see as the issue in your case is the support for the screws. Typical installation have screws biting into something supportive rather quickly. I.E. Screw through lath and 30# felt and then right into the plywood and studs. In your case the 2" of foam provides little if any support for the screw. You will have all that weight bearing down on the screw causing a bending (shear)force since 2" is unsupported. I believe you should have an engineer specify the type and screw spacing to ensure it will hold the weight without the screws breaking due to the downward force.
methierUser is Offline
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03 Sep 2010 03:29 PM
tb1472000, thanks. Yes, it does answer my question in a way and you explained the problem better than I could...
--> screw will bend since there is a 2" portion of the screw (due to the foam) that is unsupported

What you are suggesting is that an engineer should analyze the length and thickness of the screws, and how many should be used, but to keep the same general installation approach as you described in your first paragraph.

What about the other suggestions to:
- bear the stone on the footer ledge
or
- use steel angle or some other type of support

Would either of these approaches help to support the stone and reduce to need (and cost) to use long and thick screws to hold the metal lath ?

I did read the installation guide that you provided with the link, and it is similar to other versions that I had read elsewhere. I think I understand the typical installation scenario. Where I get lost is the complications due to the 2" of foam.
I was hoping that I wasn't the first person to do this and that others could offer advice based on experience with this particular approach.

Thanks,
Martin
JellyUser is Offline
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03 Sep 2010 06:14 PM
The way much thicker structural stone is supported is by bearing on a brick ledge poured with the foundation (and brick ties attached to the frame at prescribed intervals). So I think you can rest assured that your thin stone veneer would be supported if you added a brick ledge to the foundation and treated it like structural stone. Assuming your still in the design stage, it's probably not much more cost at all to have a brick ledge added. Would the foundation be a monolithic concrete pour?
methierUser is Offline
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05 Sep 2010 01:15 PM
Jelly, yes, the foundation will be poured concrete. The foundation walls will be 8" thick where the finish will be EIFS. Where we have the thin stone, we can make the walls 2" thicker (10" foundation wall) or keep them at 8".

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09 Sep 2010 11:19 PM
The cultured stone and thin veneer stone I'm familiar with specify non rigid sheathing to be a max thickness of 1/2". The product you want to use seems like wall tile. If it is a tile then you need to follow TCNA details and I doubt they have one for your application.
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10 Sep 2010 10:33 AM
Posted By methier on 29 Aug 2010 11:56 AM

Has anyone ever installed thin stone veneer (natural) over 2" XPS rigid foam ?

2x6 wall construction
1/2" plywood
tyvek or typar house wrap
Driwall rain screen 10mm
2" XPS foam
Metal lath
Scratch coat
Thin stone veneer

If so, how is the stone supported ? Due to the outwards projection caused by the foam, nails or screws to hold the metal lath is no longer sufficient.
What are the recommended solutions in this case ?

Bonus question...do I have the correct order of layers listed above ? ie: should the XPS be placed over the house wrap followed by the Driwall rainscreen, or as indicated above ?

Thanks

we did basically what you're describing, with one difference.  Our XPS was only 1" vs. 2".  The masons had no concerns about installing over it, and did basically as described in other replies - metal lathe, scratch coat, stone.  The stone we used was natural stone, but a veneer stone rather than full thickness.  The pieces varied a bit, but on average I'd say they were  1-1 1/2" thick.  We talked with the masons before starting to talk about pouring in the brick ledge, but were told we didn't need it.

jonrUser is Offline
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10 Sep 2010 02:15 PM
I agree - it isn't that screws or nails aren't sufficient, it is a matter of how big do they need to be to span 2" without bending or pulling out of the 2x6. And perhaps how much thermal bridging they create.

If you also used a brick ledge, I'd be concerned (only speculation) that the two methods (stone mortared/screwed to wall and stacked) might be incompatible due to expansion rates.
bp f150User is Offline
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19 Sep 2010 08:50 PM
After reading the post I came up with possible suggestion (with possible drawbacks, but still a solution). What if you instaled a 1 inch insulation board (only where stone veneer is to be applied) then nail or screw 1 X material to studs, then fill in voids in between with 1 inch foam (I understand that this will cause some thermal brindging but should make the set up much more structural) to get the desired thickness. Afterwards the lath could be screwed into the 1 X (longer screws could be used to compress and hold everything together) and scratch coat over. My concern would be the need for a type a drainage plain for the 1X material.

I could be totaly wrong suggesting this approach. If so I am convinced somebody will let us know. In the mean time good luck.

The house looks nice. I hope you and your family will enjoy it when the time comes.
cmkavalaUser is Offline
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21 Sep 2010 07:38 AM
bp f150;

your suggestion would work better than the full 2" that relys solely on the screw
Chris Kavala
info@southernsips dot com
1-877-321-SIPS
FL. Lic # CBC036455, GA Lic. RLCO000624, LA Lic. # CL33845
jonrUser is Offline
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21 Sep 2010 11:36 AM
Perhaps one could leave the filler foam out to maintain a drainage plane. Might take closer 1x placement or stronger mesh. I'd also consider non-wood 1x - fibercement or plastic.
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26 Dec 2010 02:39 PM
I would only 'consider' this assembly method with thin stone veneer that is essentially a stone tile in essence applied like a hard coat exterior stucco to the XPS.
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