Rolled-Edge Slab with Continuous Insulation
Tim_E
| Posted in General Questions on
Greetings,
We will wrap our garage in polyiso that continues below the slab edge to the bottom of the rolled edge slab (monolithic). The ground/sidewalk level will be 6-8″ below the slab edge. There will be a ramp from ground level to the slab edge (or slightly under).
1. How do I protect and seal the insulation sandwiched between the concrete?
2. Ideas for protecting the face of the insulation around the house.
3. Value of the shelf under the door.
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Replies
Polyiso shouldn't be used below grade because it can absorb water and it can't release the water readily.
It sounds like you're planning to make the ramp out of concrete? Foam sandwiched between layers of concrete is as well protected as it gets, other than against insects.
Here's a good overview of options for protecting foundation insulation: https://www.greenbuildingadvisor.com/article/how-to-insulate-a-basement-wall. Check out the list of related links as well. I use Styro Industries' Tuff II synthetic stucco.
What "value" do you want for the shelf under the door?
True, I misstated my use of plastic. The building is Polyiso and the slab XPS outside and load bearing and EPS underneath.
Insects and an open edge of foam is exactly what i would like to avoid (and grandchildren poking at it).
I was wondering what value the shelf brought (sorry poor wording). Is it primarily for water and maybe some air? I was giving some thought to increasing the shelf depth and placing a product there that would extend out to meet the ramp.
PS Thank you for the link
In my world, a shelf in a foundation would be similar to a brick ledge, but on the interior. I don't see that in your drawing. Are you referring to making the slab extra-thick at the overhead door by dropping the elevation of the top-of-wall? If so, the reason is to reduce the risk of cracking if the sub-slab soil subsides. At least that's why I do it.
EPS is available with a borate treatment that in my experience does a good job of keeping insects at bay. Search for "R-Control" to find a dealer near you. But it's not perfect and may be hard to find. I avoid exterior insulation whenever possible, partly for this reason.
I am considering a shelf on all exterior doors primarily for shedding water and in the case of the garage, to reduce wind past the bottom weatherstripping. I am also considering composite decking material on this ledge to encase the exterior insulation...
I think I understand now--by "shelf," you're talking about stepping down the top of slab at the overhead door. That's not really clear in your drawing. I have not done that but it's not a bad idea. Simply having the change in height wouldn't do anything for air control, but it would block water infiltration. With the right kind of weatherstripping it could help with air infiltration but it would have to seal against the vertical face of the step, not the typical type applied to the bottom of the door.
My father-in-law built his garage with a step down and with the outer edge capped with a steel angle.
Thank you Michael...