Best details for thin stone veneer exterior wall
We are renovating part of our exterior and will clad it with thin stone veneer. However, the more I read, the more confused I am in determining the best exterior wall construct. We would like to add 1.5 inch of insulation to the exterior in order to eliminate any thermal bridges (placing all insulation to the exterior is not an option at this point due to design decisions along the way). The needed wall construct seems complicated and expensive and would like some advice on how to simplify it.
exterior to interior construct in toronto or zone 5.
stone veneer
ventilation gap in the form of greenguards DC14, sure cavity or delta-dry. or is open weave plastic mat sufficient?
wrb (what about vapro shield or vapor permeable blue skinor is plain tyvek ok?)
plywood or cbu
1.5 inches of iso or xps (could blown closed cell insulation be used to replace both insulation and wrb?)
WRB(air and water barrier) should this be liquid wrb to prevent issues from insulation fasteners?
plywood
2×6 cavity with closed cell insulation or fiberglass. should we use bracing to replace plywood in previous layer?
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Replies
Christine,
I don't think your proposed layers make sense.
First of all, a warning: thin stone veneer is a very risky type of cladding, especially when installed on a wood-framed walls. Many contractors are making a good living fixing hundreds of buildings with rotting walls, all of them formerly covered with thin stone veneer ("lick-and-stick" stone).
If you really want to throw caution to the wind and install this risky cladding on your house, I suggest you follow the details in this manual: Rain Screen Designs for Absorptive Claddings.
Thanks Martin
Where would you place the exterior insulation in A01d and a01c. Should it be vapour permeable or impermeable? would you add anything else because of the insulation?
What would you recommend for the drainage spacer?
Another question Martin
Do you feel the same way about porcelain tile?
Christine,
Q. "Where would you place the exterior insulation in A01d and a01c?"
A. The rigid foam insulation should be installed between the wall sheathing and the WRB or between the WRB and the drainage board.
Q. "Should it be vapour permeable or impermeable?"
A. Most rigid foams have a low vapor permeance. Don't worry about it.
Q. "Would you add anything else because of the insulation?"
A. The foam insulation has to be thick enough to keep the wall sheathing above the dew point in winter. More information here:
Calculating the Minimum Thickness of Rigid Foam Sheathing
How to Install Rigid Foam Sheathing
Q. "What would you recommend for the drainage spacer?"
A. A wide variety of products are available, and any of them will work, as long as the product is three-dimensional and includes an air space at least 3/8 inch or 1/2 inch deep.
Q. "Do you feel the same way about porcelain tile?"
A. I have never heard of porcelain tile being used as a siding for a home in North America, although I have seen it used on the exterior of mosques in Iraq, Iran, and Uzbekistan.
Thanks Martin,
We will be using natural limestone veneer. Do you feel as negative about that as you do about manufactured stone veneer?
Just to make sure, is this what you recommend? From outside to inside.
stone veneer installation
ventilation gap in the form of greenguards DC14, sure cavity or delta-dry.
wrb
1.5 inches of iso or xps (at least r7.5)
plywood
2x6 cavity with closed cell insulation
FYI, porcelain tiles is used in Italy and Germany and is making some inroads in the design circle in canada. Of course, everyone is concerned about installation.
I’ve used the same application and the same NAHB details many times w/o any issues; you must make sure your water management details are followed correctly. I like to speck out the following 2
products for reainscreens:
1. http://www.cosella-dorken.com/bvf-ca-en/products/rainscreen/products/dry.php
2. http://www.benjaminobdyke.com/visitor/product/key/homeSlicker
thanks Armando
Although it is thin (2 inches) the stone is heavy. Will their be proper support given there is insulation between the plywood and the stone itself? My contractor seems to think so.
Martin,
"A. Most rigid foams have a low vapor permeance. Don't worry about it."
IF this is the case, should i have a drainage gap behind the insulation to allow proper moisture management ?
CAn i put closed cell insulation between the studs?
Christine,
If you decide to put all of your insulation on the exterior side of the wall sheathing (following the PERSIST method), then you can use rigid foam with drainage channels on the back side. This is one of the methods used for water-managed EIFS installations. (See the attached image). In this case, however, you would not ordinarily insulate between the studs, since there may be air flow between the rigid foam and the wall sheathing.
I hesitate to provide you with final details for your wall assembly, however, since so many of these walls have failed. You are treading dangerous waters here; this is the realm of EIFS and stone veneer installations, and you really need to come up with a bullet-proof system. Don't try to invent a new wall assembly here; get experienced advice from an installer or engineer who understands the failures that have plagued the industry.
The weight and thickness of the rain screens are minimal when compared to the weight of the lath, scratch and bedding coats, and stone; especially if you are going to install veneer rock over 2” rigid insulation or more. You should ask the manufacturer of the stone for instructions on that application or you may need to hire an engineer to do the calcs. You may need to use 1x4 strapping to the framing members and specially designed fasteners & caps. Here are a couple of good places to start:
http://www.wind-lock.com/cat-25-1-5/Fasteners.htm, http://www.ebuildingproducts.com/products.php?cat=79
Martin / Christine -
Enjoyed reading through your posts, we're working out details for a similar assembly on the exterior of a concrete foundation wall. I think there are structural concerns that probably require a ledge of some sort, and in our case that has to be below grade.
We've seen the screws through foam into sheathing sag over time, even with just Hardie siding hanging on them.
The weep screed looks like it might be a good start if it had enough structural integrity.
Thanks -
Hi JOe,
Did your the nails go through the studs or only through the sheathing? Do you know how far in they went into the studs. Was the system engineered to determine if the weight was too much? IF it was, that is concerning, if it was not, I am not sure it is of concern.
I don't think the weep screed have much structural integrity.
Christine, I find myself in a very similar situation to yours. In Zone 5, 2x6 wood framing and wanting to use 2.5" of "outsulation" - rigid XPS exterior to the plywood sheathing with stone veneer as the final siding, specifically limestone veneer (looking at Maiden Stone products). Was wondering how did it go for you? Whats was the final design? Any pearls or pitfalls you might want to share? I would greatly appreciate discussing the issue if you have time. My email: [email protected].
Regards
Build a ledge into the foundation to support the weight of the stone. Place your wall accordingly. There is too much weight to just "glue" that stuff to the wall. Let the foundation bear the load of the stone, whether it is 1,2,3 inches thick veneer.