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DaveBell
Moderator
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# Posted: 18 Mar 2017 10:44pm
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I'm looking for ideas/best practices for finishing the insulation board one has on the side of the slab. I'm insulating under the slab and assume I need to insulate the sides, entire outside of the footer up to the termite/bug shield under the framing. Or does the insulation board stop at ground level, say two inches below the bug shield?
If the insulation needs to go up to the bug shield, how would one finish it off so you are not looking at pink/silver trim?
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Nate R
Member
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# Posted: 18 Mar 2017 11:31pm
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As far as I know, you'd want the insulation to go all the way up the side of the slab.
What I've used on an old house foundation before was Styro industries fp ultra lite. Comes prefinished, seems to hold up OK and look good.
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Steve_S
Member
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# Posted: 19 Mar 2017 09:08am - Edited by: Steve_S
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I attached 2" XPS to the side of my slab with Hilti Anchors as shown below. The sides are 8" in height and also sealed to the bottom 4" XPS as well as the side edges. I then put HD Commercial Landscape fabric to cover the side and along the bottom extended "wing" which runs under the slab and out the side by 2'. That was then backfilled with 4" drainage gravel and will be topped with stone this spring... Some photo's below.
You absolutely want to insulate the sides of your slab otherwise you will radiate heat out and act as a cold sink in winter making the sides of your slab frosty WHICH IS NOT GOOD ! That will affect your heating but also frost+concrete=trouble over a short period of time.... remember that ice can and will destroy everything given the chance.
NB: I used Galvanised Steel for the flashing which are attached to cabin with galvanised roofing nails. The HD Landscape cloth is a very thick UV Safe Commercial product intended for drainage uses. Attached to cabin with Galv Staples (just under the flashing). The Hilti plugs were a PITA as you have to drill the concrete but well worth it. NOT SHOWN, is the Galv Flashing is sealed to the Wrap with TecTape to prevent water intrusion...
Hilti Anchors I used to attach the foam:
 
cloth & galv flashing being installed
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backfilling with drainage layer
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DaveBell
Moderator
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# Posted: 19 Mar 2017 11:57am
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If I insulate under the slab and around the perimeter of the slab, what about inside the footers and under the footers?
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Steve_S
Member
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# Posted: 19 Mar 2017 12:11pm
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Have a peek at this posting http://www.small-cabin.com/forum/2_7416_0.html#msg107612
I thought you were asking about a slab you already had. If your having one poured, the only solution if it is for residential use is FPSF in my opinion. There are different ways of dealing with the sides.
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DaveBell
Moderator
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# Posted: 20 Mar 2017 08:00am
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We had this discussion before but in general terms, without Air Freezing Index (AFI).
http://www.homeinnovation.com/~/media/Files/Reports/Revised-Builders-Guide-to-Frost-P rotected-Shallow-Foundations.pdf
BldgInsp mentioned the difference between his slab and a friend's slab that had Horizontal insulation.
So there is Frost Heave risk insulating requirements and added comfort insulating. For my AFI, it looks like I only need Vertical and NateR's recommendation fits the bill.
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Steve_S
Member
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# Posted: 20 Mar 2017 08:27am
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Well I don't know what Nate suggested and installing only vertical insulation seems a bit dubious as the concrete will still act as a cold sink. Just consider this... Once the concrete is poured that's it, no retrofit, no add ons... So plan for your areas Worst Case Scenario - you know, that 100 year event that will happen next winter...
Regardless of what your climate zone, insulation is never a waste... it keeps the cold out & heat in, during winter and the heat out & cold in, during summer which is always good for the pocket book and your personal comfort overall.
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