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Community and Q&A

Insects and rodents vs. foam under pole barn slab

mikeysp | Posted in General Questions on

Hi, I am in zone 4a (west of Nashville, Tennessee) and am making an insulated pole barn for use as living quarters and shop area. 

I want to insulate under the slab with EPS Type II or XPS (whichever I can find for less) as depicted in the details (below); but, I am concerned with critters moving in – rodents, termites, ants, etc… and damaging the foam.

I have no scientific reason to be concerned, just the thought that it might look inviting to these critters. 

Thank you for your advice.


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  1. Expert Member
    Zephyr7 | | #1

    I think you’re pretty safe except possibly for the edges. If you want some protection, You could use either some fiberglass window screen wrapped around the edge (cheap, but possibly chewable by determined insects), or some stainless steel screen (far more durable and totally insect proof) would protect you.

    DO NOT use aluminum window screen here — it will degrade into white powder in short order.


  2. Mike Kolder | | #2

    Bora-Foam is a termite-resistant expanded polystyrene insulation designed for basement and crawl space encapsulation. But Im leaning toward mineral wool

    1. James Someone | | #3

      I'm in 4A, southwest VA. I had a chunk of xps left outside for most of a year as an experiment, the house gets treated regularly for insects/termites as precaution. The xps was attacked by ants and wasps throughout the year. Wasps fly in a couple times a year like a plague and land on everything, even working their way into the body panels on automobiles. No exterior foam for me.

  3. Splenetic | | #4

    It should be safe and just like Zephyr7 says, be careful on the edges.

  4. Expert Member
    Malcolm Taylor | | #5


    The problem is that according to your sketch, you are proposing to extend the foam under the load-bearing parts of your foundation - which makes the consequences of any infestation a lot more serious. How you detail and protect the foam partly depends on the shape and depth of the footings. do you really have a slab with no thickened edges as your sketch shows?

  5. John Clark | | #6

    No footer?

  6. Jim Allen | | #7

    Mike says this is a pole barn. Traditional pole barn construction carries the building load into the ground through the "poles", which in most conditions similar to his would have footers poured in the bottoms of the holes. The slab generally isn't structural. The treated 2x8 on the exterior is typically fastened to the outside side of the poles, and extends below grade to function as a form board for the slab pour. The poles aren't shown in his section.

    I've never done a pole building with an insulated slab, but I would be very concerned about establishing an insect and rodent deterrent barrier around the outside of the foam. A gravel base isn't rat-proof.

  7. mikeysp | | #8

    Jim is correct, I am making a pole barn. What is not shown are the treated 6x6 posts. That 2x8 is also treated (ground contact). The reason i want insulation is because of the wet floor issue I had in my last garage 30x40. It would get wet because of the cool concrete floor and humid air touching it. I am trying to separate the cool ground from the concrete. While it was nice to help keep my work area a little cooler on hot days, the moist floor was most undesirable too me. I am going to look for some stainless or copper to protect the foam, but if unsuccessful in my budget hunt, what if I modify the concrete as shown in the following image? Will I still have those humid air wet spots along the edges?

  8. Splenetic | | #9

    I also recommend you use driveway sealers since I think it's a good way to seal your driveway, you can choose one these Best Driveway Sealer Reviews at

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