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Slab with two hydronic zones: thermal break?

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laurie71

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Apr 20, 2016
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Centerville, Ohio, USA
Planning a 36' x 56' garage divided into two internal spaces, a three car parking garage and an adjoining workshop. Footing and block wall foundation, floating slab, stick framed 2x6 @ 24 OC.

I'm planning to condition the workshop with hydronic but not the parking area, so the internal wall will be insulated and there will be PEX in the slab on the workshop side. I may run additional PEX in the parking end to have the option of hooking it up if I ever want to condition it in the future but, for now, I'll leave them not hooked up.

My question is, can I install some sort of thermal break / insulation in the slab between the two parts of the building? For example, could I form up the workshop portion, pour the slab, then form up the parking portion, and place a strip of 2" insulation foam along the existing poured edge, resulting in two independent floating slabs?

I don's see any reason why not, since foam is often used between the frost wall and slab at the perimeter. The interior wall isn't load bearing, so the foam break could be directly under it, allowing the foam to be covered and safe from varmints and other sources of damage.

Obviously not doable with a mono-pour, but with a floating slab this seems to me like it should be fine. Thoughts?
 
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GYPSY400

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Naughton Ontario
You could do it as described, I don't see a problem with it.. mind you I'm a mechanic not a builder.

My question is: are you planning on insulating the walls in the parking area? I'm assuming so, since you stated about possibly heating it in the future.. So what I'm getting at is : with no thermal break between the 2 zones the "wasted" heat from the workshop floor would essentially heat the parking area.. probably not a whole lot, but I'm guessing enough to keep it above freezing .. to me, it's a win/win.. as your not heating it directly, and your wife is not getting into a freezing car. Once the pad is warm, it will stay warm for days.

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finn

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The UP, God's country
I installed a thermal break as you described, for the same reason.

Actually, the inspector made us install it to protect the slab from thermally induced failure.
 
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Majordisorder

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North Idaho
If you use 2" for thermal breaks, sometimes it is nice to bevel it at a 45 deg angle, leaving only 1/2" showing at the top.
 
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kabinenroller

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Sep 14, 2013
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S.E. Wisconsin USA
My building is 40x60, the hydronic heated portion is 40x46. I insulted the full foundation and under the floor the same throughout the building, between the heated and non heated portion I installed 2" of ridged foam vertically to act as the thermo break, over the foam is a 6" stud wall that is insulated like the exterior walls dividing the two spaces. It works very well and I do not think there is any thermostat transfer between the two slabs.
 
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laurie71

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Location
Centerville, Ohio, USA
GYPSY400 said:
You could do it as described, I don't see a problem with it.. mind you I'm a mechanic not a builder.

My question is: are you planning on insulating the walls in the parking area? I'm assuming so, since you stated about possibly heating it in the future.. So what I'm getting at is : with no thermal break between the 2 zones the "wasted" heat from the workshop floor would essentially heat the parking area.. probably not a whole lot, but I'm guessing enough to keep it above freezing .. to me, it's a win/win.. as your not heating it directly, and your wife is not getting into a freezing car. Once the pad is warm, it will stay warm for days.

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Click to expand...

Parking section will be completely non-finished on the interior -- no insulation or drywall, minimal electrical. That's why I'm looking to limit thermal transfer from the finished, conditioned shop side.

finn said:
I installed a thermal break as you described, for the same reason.

Actually, the inspector made us install it to protect the slab from thermally induced failure.
Click to expand...

I'll have to research that, but it sounds like I'm on the right track. :beer:

Majordisorder said:
If you use 2" for thermal breaks, sometimes it is nice to bevel it at a 45 deg angle, leaving only 1/2" showing at the top.
Click to expand...

Not an issue if the foam is under the interior wall, but I think I'll adopt that tip for the foam around the perimeter -- thanks!

kabinenroller said:
My building is 40x60, the hydronic heated portion is 40x46. I insulted the full foundation and under the floor the same throughout the building, between the heated and non heated portion I installed 2" of ridged foam vertically to act as the thermo break, over the foam is a 6" stud wall that is insulated like the exterior walls dividing the two spaces. It works very well and I do not think there is any thermostat transfer between the two slabs.
Click to expand...

Sounds like *exactly* what I was thinking, thanks, good to know that plan worked well for you!
 
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Moosefire66

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Detroit
Please do a build thread when you start, that's nearly the size I'm looking to build, same design too, 3 parking spaces and a workshop

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laurie71

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Centerville, Ohio, USA
Moosefire66 said:
Please do a build thread when you start, that's nearly the size I'm looking to build, same design too, 3 parking spaces and a workshop

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Click to expand...

See my signature for link to the build thread, which will start being more active shortly as I get started in earnest. I'm having so much trouble getting any response from local concrete guys that I'm thinking about just diving in and building the foundation myself... :dunno:
 
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Radix2

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the thumb!, MI
I did as you describe to separate my shop from the garage - vertical foamboard as a thermal break - with careful bracing and pouring from both sides evenly, it was a mono pour without issue.
 
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laurie71

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Centerville, Ohio, USA
That's a good question; I had been thinking it would be effectively two independent floating slabs, but what happens if one or both heave under the non-structural interior wall? Which makes me wonder about that even if it were one continuous slab -- what happens with that interior wall if it moves?... :dunno:
 
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ishiboo

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Oshkosh, WI
I think normally a setup like this would have two separate slabs with a real wall between them... i.e. if it's a frost wall, you'd have a true frost wall in the middle to support the wall. If not, I'd plan on at least doweling the slabs so they kept on the same vertical plane where that wall is.
 
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laurie71

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Centerville, Ohio, USA
I hadn't thought to plan for a frost wall since the interior partition wall isn't meant to be load bearing. Now I'm thinking you're right, and a frost wall there would be good insurance... hmm.
 
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