Stone (not veneer) over 3″ rigid continuous exterior insulation
user-1101118
| Posted in General Questions on
Has anyone done this/have a detail/masonry clip supplier for installing stone over a continuous 3″ exterior insulation system (2×6 w sheathing) load bearing wall ? I am in climate zone 7 8000+ HDD.
I don’t wish to get into why I am using 3″ exterior rigid but I have performed the calcs for my climate. I just need help getting the stone to stay attached to the wall 🙂
I will have a typical galv angle with weep bottom support below grade.
Anyone?
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Do these have the capacity you need for stone? http://www.cascadiawindows.com/products/cascadia-clip
Are you talking full-thickness stone veneer with an air gap, or thin fully adhered? With the word "weep" I'm guessing the former, except that wouldn't be below grade, so still unsure...
Erik,
To my mind, "stone (not veneer)" means that you don't want to try to adhere (glue) the stone to the rigid foam. Instead, you want to install a traditional stone-and-mortar wall on the exterior side of the rigid foam.
If my understanding is correct, you need a concrete foundation that begins below the frost line to support this type of stone wall.
See attached image for clarification. I am wavering on the dimpleboard-do I need it? And I think? code requires a "wicking rope" where does this go? So in many cases I have the assembly transitioning form ICF to wood framed backup. I would very much appreciate feedback. I looked at the international masonry institute but they did not have a detail for this sort of scenario-which is likely more common in residential than commercial construction.
Eric,
The weep holes need to be above grade. The wicking ropes (which are an alternative to weep holes) have to lead from the bottom of the air space to the exterior (above grade).
You also need flashing at the base of the air space (the air space behind the stone) to direct water to the exterior (via the weep holes or wicks).
And Eric, that galvanized angle is not going to support the masonry, unless you've got some engineered solution for ICF. The problem is cantilevering the tremendous weight of stone veneer through the thickness of non-supporting foam. You'll have to go with one of the "masonry shelf" ICFs. There's no way to avoid the exterior thermal bridge of a concrete support for your masonry.
OK..attached is V2 (internally V5...) but based upon the feedback received.
You can reduce the thermal bridge of your steel angle stone ledger by attaching it to "knife plates" or "knife-edges" which are attached to the concrete. See Figure 2 in this article: https://buildingscience.com/documents/insights/bsi-005-a-bridge-too-far
That said, because your ICF also has insulation on the inside, this may or may not be worth the trouble.
Erik,
From the original drawing it looks as though you'd prefer to run the stone to grade - as Marin said you will want to have the weeps above grade. Can't recommend weep ropes, neither can the brick industry. I certainly recommend having a drainage mat behind the stone, which can hold a lot of moisture. I'm attaching a detail that gives the stone running to the grade, but weeps above grade. Also, pay attention at your transition - not sure what veneer is above your cap stone, but you will want to ensure your cap stone has a good slope-to drain and a flashing to transition it. Full pdfs of attached images at https://www.mtidry.com/hyperspecs/full-stone-veneer-run-to-grade-with-rigid-insulation and https://www.mtidry.com/hyperspecs/full-stone-to-stucco-transition
great feedback all. Question for tyler (#9)...does the 10mm sure cavity product meet code? Thought code required 1" of airspace? Agreed need to focus on transition, haven't much because the focus was down lower.....
Erik,
The flashing at the weep holes shouldn't be galvanized -- galvanized flashing won't last long (especially adjacent to damp mortar, which is alkaline). Lead-coated copper or EPDM flashing would be better.
Moreover, the weep holes will easily be buried in mulch if they are that close to grade. You need to get your weep holes several inches above grade. More information here: Flashing Brick Veneer.
In a brick cavity wall system a 1" drainage cavity is code, but the challenge there is getting a true 1" gap along the whole back side. In reality, the mortar droppings make such a mess that there are sections just solid with mortar in the "1 inch" cavity. Having a consistent and predictable drainage field, which a drainage mat like Sure Cavity provides, is much more important than how wide it is. Parts of Canada require a 10mm drainage gap, so the 10mm product meets code there. South of that border (aka USA) unless your local code differs from the IRC there isn't a specified drainage gap. 1x3s were sort of the old furring strip standard for convenience sake. Check with local code, but there's been a lot of testing done that shows a 10mm gap to as small as 1/8" is ample for drainage.
Check out "brick ledge ICF" or "taper top ICF" standard forms. Many manufacturer's have details online for brick/stone veneer. It will add some thermal bridging, which could be compensated by more insulation at the floor header and interior wall, or use an extra thick ICF form. Also, if you have snow, I'd place the stone veneer minimum 8" from grade, or higher if you have a lot of snow.
Gang: Took all to heart and agreed on all points. See attached "V3". I drew it so I could partially bury some stone instead of having the weird "levitating stone in the air" concept. As for ICF ledge-valid option but that seems like I can leave it up to contractor.
I agree that the 'run-to-grade' approach is more visually appealing. Last note that I'll include is that if you use a drainage mat (Sure Cavity or the like) you don't need to include the 1-2" airspace as the drainage mat is responsible for the airspace and drainage gap. Products like sure cavity have an attached fabric that keeps the drainage channels free from mortar. You can install the stone against the drainage mat or slug the cavity full with mortar, which results in a stronger wall. In areas with seismic considerations this approach is standard, and often a product such as Structolath would be used to add additional strength.