Pole barn perimeter insulation advice needed

[Dstyduhar]

Hello everyone,

I was hoping I could get some advice about the perimeter insulation on my pole barn. I have attached a pic showing the skirt detail, with a 2x8 on top of a 2x10 and some temporary midspan 2x4's to hold things together.

- The distance from the compacted sandrock pad to TOP of upper skirt is ~18inches
- TOP of the concrete will be about 4 inches down from top of upper skirt 18-4 = 14"
- The slab will be 5" thick 14"-5" = 9" inches of fill needed
- The plan is to put about 6" of crusher run down and then a few inches of 57 on top and do concrete next year.

I purchased 8 sheets of 2" 25PSI XPS foam last night. Its very difficult to get 1.5" in this part of NC, its either 1" or 2". But anyway, I plan to fasten the foam to inside of these skirt boards BEFORE we fill up the barn but not sure about the following:

Top detail

1. Should I set the foam even with where the top of where the future concrete will be? Should I do a bevel cut at top? Should I just cover the entire skirting and let the foam protrude above the concrete and cut later if needed? I plan on framing the walls in the future and still on the fence about radiant heat.

Bottom detail

1. How far down into the gravel should I run the foam? What about bugs and termites eating nesting in it and destabilizing the base under the concrete? Seems like the most straight forward solution would be to just cover both skirts in a single piece and move on. Really cant get a good feel if bugs are an issue though I have seen where folks wrap the xps in stainless mesh before being buried?

thanks,

Drew

 

[kj_mustang]

If you are framing in the walls, then run the insulation to the top of the slab since you won't see it in the future. For my radiant heated slab in my location in Virginia, I only insulated the depth of the slab on the perimeter and the entire bottom of the slab. I worried more about mice digging under the skirt and eating into the XPS than bugs.

 

[billconner]

If your concerned about frost heave, look up depth in ASCE 32. Probably not in NC. If about heating and energy efficiency, edges of slab and under it. I'd bevel tops because I'd be slow to build walls and wouldn't want to see edge if foam, but if framing walls soon, don't bother with bevel.

 

[Dstyduhar]

yeah the frost depth here is less than a foot. I have seen where some guys (likely in colder areas) painstakingly dig out below the skirt just to run the foam down further. Prob not an issue here. What about the inside of the skirting being exposed to the crushed rock? I figured the foam would help protect it a bit. I dont know....

 

[billconner]

For simplicity, I think your plan to just cover the 2x8 and 2x10 rat boards makes sense. But then 7" of gravel, 2" of foam, poly, and 5" of concrete.

 

[Juiced06GTO]

I just did this in my barn build. I have 12" of foam secured to the skirt boards, then filled and compacted 3/4" crushed stone to get me to a remaining depth of 7" or so, then laid the 15mil stego wrap vapor barrier, then 2" xps foam on top of that leaving me with a minimum of 5" depth concrete slab, 4kpsi with wire mesh. I left the foam out under where I plan to mount a lift in two 3'x6' pads and built a rebar cage so there is a 3x6 rebar and mesh reinforced 7" thick footing allowing some flexibility in where the lift goes. I also routed my radiant around these areas and stapled the pex to the foam under the mesh. The pex keeps the mesh up off the bottom so it is not at the very base of your slab.

I didn't bother with beveling the tops as they will be behind the walls, I did however leave the foam down about an inch and a half around the posts as it would have shown on the floor outside the finished walls.

Make sure that you bring the grade up around the outside of your building first so the skirt boards are supported otherwise when you fill and compact the inside it will bow the skirts out and cause you all sorts of issues. I've got a ton of pictures in my build thread if ya need a visual. Good luck with the build!! Any questions feel free to shoot them my way!

 

[fatboy99]

Here is a great video with lots of good tips