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Monolithic slab insulation

Sifu

Sifu

SAWHORSE
Joined
Sep 3, 2011
Messages
3,320
Codes require insulation be installed from the top of the slab down vertically and/or horizontally for the prescriptive depth. Codes also require that the exterior wall on top of this slab be 6" above the exterior grade. This means that 6" of 2" insulation will be exposed. I am having "trouble" with this application. If anyone can suggest workable methods for protecting this insulation I would be happy to hear them. So far about the only thing I can come up with is bending a kick out flashing out and over and down. That will look bad and obviously the builders I am introducing this to are not happy. I also think this will be damaged in fairly short order by a homeowner/landscaper or building owner (commercial) and then the intent of the code would be defeated anyway. I would like to come with a workable solution to make it an easier code to swallow and a lasting solution as well. Some adjoining jurisdictions have been allowing them to insulate under the slab inside the building, in fact my last jurisdiction did this as well. I never liked it because it leaves the slab edge open to direct energy transfer. Thoughts?
 
it can also be covered with pressure treated plywood. i have also installed a fiber-mesh sort of stucco ( don't remember the actual name of the produt) that trowels onto the styrofoam insulation, that is fairly substantial. it was years ago, so i don't have particulars. check wirth supply houses and styrofoam manufacturers for their products. get creative. necessity is the mother of invention

noah webster wrote the dictionary, daniel webster was a statesmen
 
mjesse said:
A parge coat or product similar to this http://www.akonallc.com/residential/mortars/foundation_coating.html works for me.(not advertisement, just a product I've seen around here)

mj
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I agree with mjesse, and not to make an advertisement out of this either, accrocrete was the regional protective product we used....similar to an EIFS system. If I remember correctly, a lot of manufacturers have CAD details and digital specification sheets you can easily integrate into your construction documents. what is your frost depth robert?
 
So is the consensus so far that there is no magic bullet, no other or better way to comply with the code than to insulate the exterior of the monolithic footing then cover and protect it in some way? It is the only way I come up with but I figure there has got to be someone smarter than me.
 
Robert S said:
So is the consensus so far that there is no magic bullet, no other or better way to comply with the code than to insulate the exterior of the monolithic footing then cover and protect it in some way? It is the only way I come up with but I figure there has got to be someone smarter than me.
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I will give it some more thought and research...but you are up against a typically tight lipped design industry and the status quo of good enough.
 
If the slab has radiant heat installed then the exterior slab insulation is a minimum R-10 plus an additional R-5 for a total R-15 requirement. See Table 402.1.1 footnote D of the energy code
 
R318.4 prohibits foam plastic below grade and restricts it within 6" of grade in Very Heavy termite infestation areas.
 
No radiant heat here, not considered a "very heavy" termite area either. The zone here requires R10 for 2'. I just thought I would check to see if anyone had any ideas but I'm not going to lose sleep over it. At the end of the day it is up to them to figure it out, I just like to offer options if it helps ease the pain.
 
JMORRISON said:
2x6 sill plate hang out two inches to cover top of insulation. Still have to cover face with sheet metal or fake stucco.
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How do you approve such a design when it does not jive with R602.3?
 
JMORRISON said:
Table 602.3(5) 2x4 wall will support one floor + roof/ceiling at 16"oc. 2x6 is just to get the required insulation depth
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Agreed - 2x4 would suffice. However, if you have a 2x6 wall, the bottom plate should be bearing full width.
 
Exactly, Mt.

Also - you can have all kinds of problems with keeping the anchor bolts and washers properly located on the bottom plate, and not violating minimum edge distances, espeically if we're talking about retro-fit anchors.
 
I have used a detail similar to JMORRISON’s for over 25 years with no difficulties. The detail I’ve used cantilevers the 2x6 plate 1 ½" not 2" (note; shear stresses may be neglected within the depth of the member), with the ½" sheathing the total projection is 2" which “flushes out” with 2" of rigid insulation. For protection I use 26ga. Pre-finished roll flashing (very economical and available at most home improvement stores).
 
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